K2 battery endurance [Archive]

Eric Greenwell[_4_]

May 8th 20, 09:18 PM

John Silverberg wrote on 5/8/2020 12:21 PM:
> Hi,
>
> I'm hoping someone with experience with K2 batteries can help determine if mine are due for replacement. I have dual K2 batteries wired in parallel to supply avionics power. I have an LX9000, S8 and V8 varios, trig transponder, FLARM core, and becker com radio running off them. I'm not sure how old they are but they're at least 3 years old as this is my 3rd season with the ship. Yesterday, after a little over 5 hours I got a low battery warning with the batteries at 11.3 volts. I had all the above avionics on but did virtually no transmitting on the com, just listening. They were fully charged at takeoff.
>
> I'm not sure if this normal endurance for these batteries or not, any advice would be appreciated.

I recommend charging each battery separately and completely, then doing a
discharge test on each battery individually at it's 20 hour rate. For example,
discharge the 10 AH battery at 0.5 amps during the test.

While the test is under way, determine the current draw of your instruments. I'd
guess it's high, and over 1.5 amps at 12.8 volts.

Once you know your current draw and the capacity of each battery, you can consider
your options.

If you decide to replace them, try to use a single 20AH battery, instead of
paralleling two 10 AH units, or perhaps a single 15AH if size matters.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorgliders/publications/download-the-guide-1

[email protected]

May 8th 20, 09:23 PM

On Friday, May 8, 2020 at 3:21:11 PM UTC-4, John Silverberg wrote:
> Hi,
>
> I'm hoping someone with experience with K2 batteries can help determine if mine are due for replacement. I have dual K2 batteries wired in parallel to supply avionics power. I have an LX9000, S8 and V8 varios, trig transponder, FLARM core, and becker com radio running off them. I'm not sure how old they are but they're at least 3 years old as this is my 3rd season with the ship. Yesterday, after a little over 5 hours I got a low battery warning with the batteries at 11.3 volts. I had all the above avionics on but did virtually no transmitting on the com, just listening. They were fully charged at takeoff.
>
> I'm not sure if this normal endurance for these batteries or not, any advice would be appreciated.
>
> Thanks,
>
> John S.

John: At 3 years of age the batteries (I assume they are LiFePO4 type) should hold almost as much charge as new ones, assuming they were stored under reasonable conditions (not in a hot trailer). You know from your experience what is normal endurance with your avionics, so compare with that. If this is way lower than normal then that's bad news. But try recharging them and trying again, perhaps the capacity will return. Was this the first use after the winter lay-over? Some types of batteries need "exercise" after a long rest, although LiFePO4 are less prone to that AFAIK. If there is still an issue, try using one battery at a time, perhaps one is bad but the other still good.

May 8th 20, 09:28 PM

On Friday, May 8, 2020 at 12:21:11 PM UTC-7, John Silverberg wrote:
> Hi,
>
> I'm hoping someone with experience with K2 batteries can help determine if mine are due for replacement. I have dual K2 batteries wired in parallel to supply avionics power. I have an LX9000, S8 and V8 varios, trig transponder, FLARM core, and becker com radio running off them. I'm not sure how old they are but they're at least 3 years old as this is my 3rd season with the ship. Yesterday, after a little over 5 hours I got a low battery warning with the batteries at 11.3 volts. I had all the above avionics on but did virtually no transmitting on the com, just listening. They were fully charged at takeoff.
>
> I'm not sure if this normal endurance for these batteries or not, any advice would be appreciated.
>
> Thanks,
>
> John S.

I am not sure which K2 batteries you are using, but they are likely at the end of their life. I have all of the avionics you have, and am drawing 2 - 2.1 A at a higher voltage (meaning you are drawing even more). I put in a Bioenno 20AH lithium battery and it can handle an 8 hr flight. You should only be discharging an SLA battery no more than 50% of its capacity.

Tom

[email protected]

May 8th 20, 09:33 PM

My 8 year old 9 Amp Hour K2 battery, just tested about a month ago, delivered 8.33 Amp Hours at a 1 amp rate. Capacity new was right at 9 Amp Hours.

Danny Brotto

[email protected]

May 8th 20, 09:55 PM

There was a thread about this, K2's mentioned, a rew years ago that Steve Keorner replied too. He asked the K2 engineers about reduced capacity he was getting, IIRC, their answer was to leave them on the charger for weeks at a time so they can balancecout the cells with the BMS on board.

CH

Dave Springford

May 8th 20, 10:00 PM

The batteries are most likely not at the end of their life.

There are a few things that you can do.

1. Check the battery type on your LX9000, is it set to LiFe?
2. Check the voltage reported by the LX9000 and compare it to the voltage reported by another instrument. Most radios have a voltage readout and often this is more accurate than the 9000 readout. IF they are different use hte voltage offset function in the 9000 to have it read the same voltage as the radio.
3. If 1 and 2 don't help, put the K2 batteries on an extended 10 day charge cycle. This helps balance the cells and restore capacity in the K2's.
4. If this doesn't work, put them on a longer 20-30 day charge cycle.

The K2 batteries should never be stored for a long duration at full charge. Always store them at about 1/2 charge and then when they come out of storage put them on a 10 day float charge. Do this once a year.

Bob Youngblood

May 8th 20, 10:41 PM

Piet Barber

May 9th 20, 02:37 AM

On Friday, May 8, 2020 at 3:21:11 PM UTC-4, John Silverberg wrote:
> Hi,
>
> I'm hoping someone with experience with K2 batteries can help determine if mine are due for replacement. I have dual K2 batteries wired in parallel to supply avionics power. I have an LX9000, S8 and V8 varios, trig transponder, FLARM core, and becker com radio running off them.

I'm guessing your LX9000 was the one making the complaints about the battery levels, right? Under the Hardware settings, what setting do you have for a battery? The LXNav flight computer doesn't have a "K2 Battery" setting. You should consider going into the setup page, go to hardware, select battery type and select "Custom"
For the battery settings under "Custom" enter the numbers they have printed on the side of the K2 battery. The numbers, as listed on the side of the K2 battery are:

Discharge Voltage Cutoff | 10.0V

That number is the absolute bitter end of the battery. I wouldn't recommend discharging your battery all the way to that level! But theoretically you can set the custom settings to that number for the "this whole system could shut off at any moment" value. Try playing around with the numbers to see what you can come up with that seems right.

I remember going into this setting immediately after turning on the system, finding out what the maximum battery charge is.

If you choose one of the other settings like Lead Acid, LiFe or LiPO, the numbers aren't quite right. I have a two seater, and like clockwork, I turn on the system and the passenger says, "Uh, the battery meter is already showing yellow"

Richard Pfiffner[_2_]

May 9th 20, 03:08 AM

On Friday, May 8, 2020 at 6:37:33 PM UTC-7, Piet Barber wrote:
> On Friday, May 8, 2020 at 3:21:11 PM UTC-4, John Silverberg wrote:
> > Hi,
> >
> > I'm hoping someone with experience with K2 batteries can help determine if mine are due for replacement. I have dual K2 batteries wired in parallel to supply avionics power. I have an LX9000, S8 and V8 varios, trig transponder, FLARM core, and becker com radio running off them.
>
> I'm guessing your LX9000 was the one making the complaints about the battery levels, right? Under the Hardware settings, what setting do you have for a battery? The LXNav flight computer doesn't have a "K2 Battery" setting. You should consider going into the setup page, go to hardware, select battery type and select "Custom"
> For the battery settings under "Custom" enter the numbers they have printed on the side of the K2 battery. The numbers, as listed on the side of the K2 battery are:
>
> Discharge Voltage Cutoff | 10.0V
>
> That number is the absolute bitter end of the battery. I wouldn't recommend discharging your battery all the way to that level! But theoretically you can set the custom settings to that number for the "this whole system could shut off at any moment" value. Try playing around with the numbers to see what you can come up with that seems right.
>
> I remember going into this setting immediately after turning on the system, finding out what the maximum battery charge is.
>
> If you choose one of the other settings like Lead Acid, LiFe or LiPO, the numbers aren't quite right. I have a two seater, and like clockwork, I turn on the system and the passenger says, "Uh, the battery meter is already showing yellow"

Read before you comment on how to charge a LiFEPO4 Battery

https://www.planetanalog.com/how-to-charge-lithium-iron-phosphate-rechargeable-batteries/#

Richard
www.craggyaero.com

Eric Greenwell[_4_]

May 9th 20, 04:29 AM

Piet Barber wrote on 5/8/2020 6:37 PM:
> On Friday, May 8, 2020 at 3:21:11 PM UTC-4, John Silverberg wrote:
>> Hi,
>>
>> I'm hoping someone with experience with K2 batteries can help determine if mine are due for replacement. I have dual K2 batteries wired in parallel to supply avionics power. I have an LX9000, S8 and V8 varios, trig transponder, FLARM core, and becker com radio running off them.
>
> I'm guessing your LX9000 was the one making the complaints about the battery levels, right? Under the Hardware settings, what setting do you have for a battery? The LXNav flight computer doesn't have a "K2 Battery" setting. You should consider going into the setup page, go to hardware, select battery type and select "Custom"
> For the battery settings under "Custom" enter the numbers they have printed on the side of the K2 battery. The numbers, as listed on the side of the K2 battery are:
>
> Discharge Voltage Cutoff | 10.0V
>
> That number is the absolute bitter end of the battery. I wouldn't recommend discharging your battery all the way to that level! But theoretically you can set the custom settings to that number for the "this whole system could shut off at any moment" value. Try playing around with the numbers to see what you can come up with that seems right.
>
> I remember going into this setting immediately after turning on the system, finding out what the maximum battery charge is.
>
> If you choose one of the other settings like Lead Acid, LiFe or LiPO, the numbers aren't quite right. I have a two seater, and like clockwork, I turn on the system and the passenger says, "Uh, the battery meter is already showing yellow"
>
At 11.3 volts, the K2 battery should have very little charge left, less than 5%.
The setting is OK as an endpoint, but you need to determine that the 9000 is
measuring the voltage accurately. If not, fix the measurement, or adjust the 9000
alarm point until it alarms when the battery is 11.3-11.7.

But, first measure the capacity of each battery.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorgliders/publications/download-the-guide-1

May 9th 20, 05:21 AM

On Friday, May 8, 2020 at 8:29:23 PM UTC-7, Eric Greenwell wrote:
> Piet Barber wrote on 5/8/2020 6:37 PM:
> > On Friday, May 8, 2020 at 3:21:11 PM UTC-4, John Silverberg wrote:
> >> Hi,
> >>
> >> I'm hoping someone with experience with K2 batteries can help determine if mine are due for replacement. I have dual K2 batteries wired in parallel to supply avionics power. I have an LX9000, S8 and V8 varios, trig transponder, FLARM core, and becker com radio running off them.
> >
> > I'm guessing your LX9000 was the one making the complaints about the battery levels, right? Under the Hardware settings, what setting do you have for a battery? The LXNav flight computer doesn't have a "K2 Battery" setting. You should consider going into the setup page, go to hardware, select battery type and select "Custom"
> > For the battery settings under "Custom" enter the numbers they have printed on the side of the K2 battery. The numbers, as listed on the side of the K2 battery are:
> >
> > Discharge Voltage Cutoff | 10.0V
> >
> > That number is the absolute bitter end of the battery. I wouldn't recommend discharging your battery all the way to that level! But theoretically you can set the custom settings to that number for the "this whole system could shut off at any moment" value. Try playing around with the numbers to see what you can come up with that seems right.
> >
> > I remember going into this setting immediately after turning on the system, finding out what the maximum battery charge is.
> >
> > If you choose one of the other settings like Lead Acid, LiFe or LiPO, the numbers aren't quite right. I have a two seater, and like clockwork, I turn on the system and the passenger says, "Uh, the battery meter is already showing yellow"
> >
> At 11.3 volts, the K2 battery should have very little charge left, less than 5%.
> The setting is OK as an endpoint, but you need to determine that the 9000 is
> measuring the voltage accurately. If not, fix the measurement, or adjust the 9000
> alarm point until it alarms when the battery is 11.3-11.7.
>
> But, first measure the capacity of each battery.
>
> --
> Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
> - "A Guide to Self-Launching Sailplane Operation"
> https://sites.google.com/site/motorgliders/publications/download-the-guide-1

One thing that comes to mind is how did you know that the batteries were fully charged? The charger may have shut off for some unknown reason. I never fully trust battery chargers and double-check their operation with a battery monitor:
https://www.amazon.com/gp/product/B00C1BZSYO/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
Most of the time the charger and the monitor agree within the margin of error, but occasionally there is a significant disagreement.

And, speaking of battery chargers, which charger are you using?

Tom

[email protected]

May 9th 20, 01:54 PM

> after a little over 5 hours I got a low battery warning with the batteries at 11.3 volts.

It might be worth checking at the batt terminals just to make sure something didn't get loose.

John Silverberg

May 9th 20, 05:34 PM

On Friday, May 8, 2020 at 3:21:11 PM UTC-4, John Silverberg wrote:
> Hi,
>
> I'm hoping someone with experience with K2 batteries can help determine if mine are due for replacement. I have dual K2 batteries wired in parallel to supply avionics power. I have an LX9000, S8 and V8 varios, trig transponder, FLARM core, and becker com radio running off them. I'm not sure how old they are but they're at least 3 years old as this is my 3rd season with the ship. Yesterday, after a little over 5 hours I got a low battery warning with the batteries at 11.3 volts. I had all the above avionics on but did virtually no transmitting on the com, just listening. They were fully charged at takeoff.
>
> I'm not sure if this normal endurance for these batteries or not, any advice would be appreciated.
>
> Thanks,
>
> John S.

Hi,

Thanks for all the information, I have some good ideas to work from now. I use the proper K2 charger and usually charge the batteries overnight. Temperature may have been a player too as it was -17C at cloud base (over 10,000' very unusual for the Northeast) and the batteries are behind the rear bulkhead on a Ventus so I'm sure they were cold soaked.

Thanks again for all the info.

[email protected]

May 10th 20, 06:06 PM

On Friday, May 8, 2020 at 4:55:35 PM UTC-4, wrote:
> There was a thread about this, K2's mentioned, a rew years ago that Steve Keorner replied too. He asked the K2 engineers about reduced capacity he was getting, IIRC, their answer was to leave them on the charger for weeks at a time so they can balancecout the cells with the BMS on board.
>
> CH

Question: I don't know about K2 batteries and chargers specifically, but generally I thought the BMS in LiFePO4 batteries disconnects completely from the charger once some maximum battery voltage is reached. How, then, does leaving them wired together for "weeks" going to do anything?

Perhaps over time the battery voltage drops back somewhat and the BMS re-engages with the charger?

[email protected]

May 10th 20, 06:40 PM

On Sunday, May 10, 2020 at 10:06:53 AM UTC-7, wrote:
> On Friday, May 8, 2020 at 4:55:35 PM UTC-4, wrote:
> > There was a thread about this, K2's mentioned, a rew years ago that Steve Keorner replied too. He asked the K2 engineers about reduced capacity he was getting, IIRC, their answer was to leave them on the charger for weeks at a time so they can balancecout the cells with the BMS on board.
> >
> > CH
>
> Question: I don't know about K2 batteries and chargers specifically, but generally I thought the BMS in LiFePO4 batteries disconnects completely from the charger once some maximum battery voltage is reached. How, then, does leaving them wired together for "weeks" going to do anything?
>
> Perhaps over time the battery voltage drops back somewhat and the BMS re-engages with the charger?

The internal BMS itself has a top balancer. It will detect when one or more of the cells are undercharged and very slowly discharge the others to first equalize them, then top them all off together. This may happen multiple times over a fairly long time until all cells are equalized since the undercharged cells themselves are unequally so. This can happen by passive balancing (resistive) or active (energy transfer from one cell to another).

I have seen my charger cycle when charging my LFP batteries (it's not K2 though).

There is no hard disconnect. Monitoring by the BMS is continuous.

David

[email protected]

May 10th 20, 06:50 PM

On Sunday, May 10, 2020 at 1:40:44 PM UTC-4, wrote:
> On Sunday, May 10, 2020 at 10:06:53 AM UTC-7, wrote:
> > On Friday, May 8, 2020 at 4:55:35 PM UTC-4, wrote:
> > > There was a thread about this, K2's mentioned, a rew years ago that Steve Keorner replied too. He asked the K2 engineers about reduced capacity he was getting, IIRC, their answer was to leave them on the charger for weeks at a time so they can balancecout the cells with the BMS on board.
> > >
> > > CH
> >
> > Question: I don't know about K2 batteries and chargers specifically, but generally I thought the BMS in LiFePO4 batteries disconnects completely from the charger once some maximum battery voltage is reached. How, then, does leaving them wired together for "weeks" going to do anything?
> >
> > Perhaps over time the battery voltage drops back somewhat and the BMS re-engages with the charger?
>
> The internal BMS itself has a top balancer. It will detect when one or more of the cells are undercharged and very slowly discharge the others to first equalize them, then top them all off together. This may happen multiple times over a fairly long time until all cells are equalized since the undercharged cells themselves are unequally so. This can happen by passive balancing (resistive) or active (energy transfer from one cell to another).
>
>
> I have seen my charger cycle when charging my LFP batteries (it's not K2 though).
>
> There is no hard disconnect. Monitoring by the BMS is continuous.
>
> David

So you concur with the BMS-reconnects-over-time hypothesis.

I usually charge my battery with my iMax B6 charger because it shows me what's going on, voltage and mAH. But when the battery reaches about 14.6V my battery's BMS disconnects - a bit before that charger would have stopped the charge anyway. And that charger then complains loudly about the connection being lost, and won't restart automatically.

If I want to give the battery BMS time to balance the cells further, I'd need to put it on a different charger. Would connecting the battery at that point to a "dumb" fixed-voltage source of about 14V be a good idea? Would using an SLA charger that aims for a "float" at 13.6V or so be a good idea?

[email protected]

May 10th 20, 07:10 PM

On Sunday, May 10, 2020 at 10:50:22 AM UTC-7, wrote:
> On Sunday, May 10, 2020 at 1:40:44 PM UTC-4, wrote:
> > On Sunday, May 10, 2020 at 10:06:53 AM UTC-7, wrote:
> > > On Friday, May 8, 2020 at 4:55:35 PM UTC-4, wrote:
> > > > There was a thread about this, K2's mentioned, a rew years ago that Steve Keorner replied too. He asked the K2 engineers about reduced capacity he was getting, IIRC, their answer was to leave them on the charger for weeks at a time so they can balancecout the cells with the BMS on board.
> > > >
> > > > CH
> > >
> > > Question: I don't know about K2 batteries and chargers specifically, but generally I thought the BMS in LiFePO4 batteries disconnects completely from the charger once some maximum battery voltage is reached. How, then, does leaving them wired together for "weeks" going to do anything?
> > >
> > > Perhaps over time the battery voltage drops back somewhat and the BMS re-engages with the charger?
> >
> > The internal BMS itself has a top balancer. It will detect when one or more of the cells are undercharged and very slowly discharge the others to first equalize them, then top them all off together. This may happen multiple times over a fairly long time until all cells are equalized since the undercharged cells themselves are unequally so. This can happen by passive balancing (resistive) or active (energy transfer from one cell to another).
> >
> >
> > I have seen my charger cycle when charging my LFP batteries (it's not K2 though).
> >
> > There is no hard disconnect. Monitoring by the BMS is continuous.
> >
> > David
>
> So you concur with the BMS-reconnects-over-time hypothesis.
>
> I usually charge my battery with my iMax B6 charger because it shows me what's going on, voltage and mAH. But when the battery reaches about 14.6V my battery's BMS disconnects - a bit before that charger would have stopped the charge anyway. And that charger then complains loudly about the connection being lost, and won't restart automatically.
>
> If I want to give the battery BMS time to balance the cells further, I'd need to put it on a different charger. Would connecting the battery at that point to a "dumb" fixed-voltage source of about 14V be a good idea? Would using an SLA charger that aims for a "float" at 13.6V or so be a good idea?

With my battery (Stark Power) and charger (see below) this is not just a hypothesis.

The BMS in all LFPs may not have the same functionality regarding balancing but at the very least they should start/stop accepting charge appropriately.

Yes, my charger behaves like a dumb power supply with an LED that shows if the battery is drawing current (>300mA) or not. All the logic is in the BMS not the charger.

See photo here:

https://photos.app.goo.gl/gcC4gB98fNUag5g39

kinsell

May 14th 20, 04:00 AM

On 5/10/20 12:10 PM, wrote:
> On Sunday, May 10, 2020 at 10:50:22 AM UTC-7, wrote:
>> On Sunday, May 10, 2020 at 1:40:44 PM UTC-4, wrote:
>>> On Sunday, May 10, 2020 at 10:06:53 AM UTC-7, wrote:
>>>> On Friday, May 8, 2020 at 4:55:35 PM UTC-4, wrote:
>>>>> There was a thread about this, K2's mentioned, a rew years ago that Steve Keorner replied too. He asked the K2 engineers about reduced capacity he was getting, IIRC, their answer was to leave them on the charger for weeks at a time so they can balancecout the cells with the BMS on board.
>>>>>
>>>>> CH
>>>>
>>>> Question: I don't know about K2 batteries and chargers specifically, but generally I thought the BMS in LiFePO4 batteries disconnects completely from the charger once some maximum battery voltage is reached. How, then, does leaving them wired together for "weeks" going to do anything?
>>>>
>>>> Perhaps over time the battery voltage drops back somewhat and the BMS re-engages with the charger?
>>>
>>> The internal BMS itself has a top balancer. It will detect when one or more of the cells are undercharged and very slowly discharge the others to first equalize them, then top them all off together. This may happen multiple times over a fairly long time until all cells are equalized since the undercharged cells themselves are unequally so. This can happen by passive balancing (resistive) or active (energy transfer from one cell to another).
>>>
>>>
>>> I have seen my charger cycle when charging my LFP batteries (it's not K2 though).
>>>
>>> There is no hard disconnect. Monitoring by the BMS is continuous.
>>>
>>> David
>>
>> So you concur with the BMS-reconnects-over-time hypothesis.
>>
>> I usually charge my battery with my iMax B6 charger because it shows me what's going on, voltage and mAH. But when the battery reaches about 14.6V my battery's BMS disconnects - a bit before that charger would have stopped the charge anyway. And that charger then complains loudly about the connection being lost, and won't restart automatically.
>>
>> If I want to give the battery BMS time to balance the cells further, I'd need to put it on a different charger. Would connecting the battery at that point to a "dumb" fixed-voltage source of about 14V be a good idea? Would using an SLA charger that aims for a "float" at 13.6V or so be a good idea?
>
> With my battery (Stark Power) and charger (see below) this is not just a hypothesis.
>
> The BMS in all LFPs may not have the same functionality regarding balancing but at the very least they should start/stop accepting charge appropriately.
>

It matters not what you think should happen, the truth is not all LFP
batteries have a BMS, and of those that do, not all of them protect from
over and under voltage.

May 25th 20, 10:20 PM

On Wednesday, May 13, 2020 at 8:00:09 PM UTC-7, kinsell wrote:
> On 5/10/20 12:10 PM, wrote:
> > On Sunday, May 10, 2020 at 10:50:22 AM UTC-7, wrote:
> >> On Sunday, May 10, 2020 at 1:40:44 PM UTC-4, wrote:
> >>> On Sunday, May 10, 2020 at 10:06:53 AM UTC-7, wrote:
> >>>> On Friday, May 8, 2020 at 4:55:35 PM UTC-4, wrote:
> >>>>> There was a thread about this, K2's mentioned, a rew years ago that Steve Keorner replied too. He asked the K2 engineers about reduced capacity he was getting, IIRC, their answer was to leave them on the charger for weeks at a time so they can balancecout the cells with the BMS on board.
> >>>>>
> >>>>> CH
> >>>>
> >>>> Question: I don't know about K2 batteries and chargers specifically, but generally I thought the BMS in LiFePO4 batteries disconnects completely from the charger once some maximum battery voltage is reached. How, then, does leaving them wired together for "weeks" going to do anything?
> >>>>
> >>>> Perhaps over time the battery voltage drops back somewhat and the BMS re-engages with the charger?
> >>>
> >>> The internal BMS itself has a top balancer. It will detect when one or more of the cells are undercharged and very slowly discharge the others to first equalize them, then top them all off together. This may happen multiple times over a fairly long time until all cells are equalized since the undercharged cells themselves are unequally so. This can happen by passive balancing (resistive) or active (energy transfer from one cell to another).
> >>>
> >>>
> >>> I have seen my charger cycle when charging my LFP batteries (it's not K2 though).
> >>>
> >>> There is no hard disconnect. Monitoring by the BMS is continuous.
> >>>
> >>> David
> >>
> >> So you concur with the BMS-reconnects-over-time hypothesis.
> >>
> >> I usually charge my battery with my iMax B6 charger because it shows me what's going on, voltage and mAH. But when the battery reaches about 14.6V my battery's BMS disconnects - a bit before that charger would have stopped the charge anyway. And that charger then complains loudly about the connection being lost, and won't restart automatically.
> >>
> >> If I want to give the battery BMS time to balance the cells further, I'd need to put it on a different charger. Would connecting the battery at that point to a "dumb" fixed-voltage source of about 14V be a good idea? Would using an SLA charger that aims for a "float" at 13.6V or so be a good idea?
> >
> > With my battery (Stark Power) and charger (see below) this is not just a hypothesis.
> >
> > The BMS in all LFPs may not have the same functionality regarding balancing but at the very least they should start/stop accepting charge appropriately.
> >
>
> It matters not what you think should happen, the truth is not all LFP
> batteries have a BMS, and of those that do, not all of them protect from
> over and under voltage.

Which LFP batteries don't have a BMS?

Tom

Eric Greenwell[_4_]

May 26th 20, 04:47 AM

2G wrote on 5/25/2020 2:20 PM:
> On Wednesday, May 13, 2020 at 8:00:09 PM UTC-7, kinsell wrote:
....
>>>
>>> The BMS in all LFPs may not have the same functionality regarding balancing but at the very least they should start/stop accepting charge appropriately.
>>>
>>
>> It matters not what you think should happen, the truth is not all LFP
>> batteries have a BMS, and of those that do, not all of them protect from
>> over and under voltage.
>
> Which LFP batteries don't have a BMS?
>
> Tom

The "powersports" (ie, for engine starting) LFP don't always have a BMS. A
motorglider pilot might be tempted to use one for the engine, for example.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorgliders/publications/download-the-guide-1

May 30th 20, 03:50 PM

One of my early K2's experienced a cell failure which dropped that battery's voltage output and lowered it's capacity. I run two batteries in parallel and had an experience like yours. Individual testing of each found the bad battery. Replacement is the only fix for this.

Battery testing can be done pretty easily and low tech. Using a voltmeter and 12V side marker lights from your local tractor supply. , 2-4 of the side marker lights should approximate your gliders normal electrical load. Plug them into the battery then check and record the voltage every half hour until it drops to 11.5V.

You can measure amperage with most multi-meters, just be careful to switch the leads back to voltage measurement. The cheap meters are not fused. Had a guy blow one up checking 480V with an un-fused meter set to measure current. It can cause serious injury, so exercise caution. The batteries we use in sailplanes can deliver enough energy to melt things if shorted out, so respect that potential when dealing with them. We had to evacuate a 300,000 SQFT manufacturing facility once because a technician shorted out a single lithium Ion battery cell in his test stand, The smoke from off-gassing was impressive.

SF

kinsell

May 30th 20, 10:46 PM

Testing is always good, but John has a very reasonable suspicion the
problem was due to cold soaking the batteries. LFP's really don't like
the cold, and can even be damaged if charged below freezing. Maybe he
had a temporary loss of capacity that wouldn't show up under room temp
testing.

On 5/30/20 8:50 AM, SF wrote:
> One of my early K2's experienced a cell failure which dropped that battery's voltage output and lowered it's capacity. I run two batteries in parallel and had an experience like yours. Individual testing of each found the bad battery. Replacement is the only fix for this.
>
> Battery testing can be done pretty easily and low tech. Using a voltmeter and 12V side marker lights from your local tractor supply. , 2-4 of the side marker lights should approximate your gliders normal electrical load. Plug them into the battery then check and record the voltage every half hour until it drops to 11.5V.
>
> You can measure amperage with most multi-meters, just be careful to switch the leads back to voltage measurement. The cheap meters are not fused. Had a guy blow one up checking 480V with an un-fused meter set to measure current. It can cause serious injury, so exercise caution. The batteries we use in sailplanes can deliver enough energy to melt things if shorted out, so respect that potential when dealing with them. We had to evacuate a 300,000 SQFT manufacturing facility once because a technician shorted out a single lithium Ion battery cell in his test stand, The smoke from off-gassing was impressive.
>
> SF
>

[email protected]

May 31st 20, 03:15 PM

On Saturday, May 30, 2020 at 5:47:01 PM UTC-4, kinsell wrote:
> Testing is always good, but John has a very reasonable suspicion the
> problem was due to cold soaking the batteries. LFP's really don't like
> the cold, and can even be damaged if charged below freezing. Maybe he
> had a temporary loss of capacity that wouldn't show up under room temp
> testing.

LFPs don't like to be charged while cold (below the freezing point of water is the rule of thumb, even though they are not made of water). But they discharge just fine while (reasonably) cold. Their capacity while cold doesn't suffer anything like the way SLAs capacity does.

[email protected]

May 31st 20, 04:03 PM

On Sunday, May 31, 2020 at 4:15:11 PM UTC+2, wrote:
> On Saturday, May 30, 2020 at 5:47:01 PM UTC-4, kinsell wrote:
> > Testing is always good, but John has a very reasonable suspicion the
> > problem was due to cold soaking the batteries. LFP's really don't like
> > the cold, and can even be damaged if charged below freezing. Maybe he
> > had a temporary loss of capacity that wouldn't show up under room temp
> > testing.
>
> LFPs don't like to be charged while cold (below the freezing point of water is the rule of thumb, even though they are not made of water). But they discharge just fine while (reasonably) cold. Their capacity while cold doesn't suffer anything like the way SLAs capacity does.

FYI the capacity does still suffer somewhat, -20% at -10c, http://liionbms.com/pdf/kokam/SLPB100216216H_40Ah%20Nano.pdf

kinsell

June 2nd 20, 03:13 AM

On 5/31/20 9:03 AM, wrote:
> On Sunday, May 31, 2020 at 4:15:11 PM UTC+2, wrote:
>> On Saturday, May 30, 2020 at 5:47:01 PM UTC-4, kinsell wrote:
>>> Testing is always good, but John has a very reasonable suspicion the
>>> problem was due to cold soaking the batteries. LFP's really don't like
>>> the cold, and can even be damaged if charged below freezing. Maybe he
>>> had a temporary loss of capacity that wouldn't show up under room temp
>>> testing.
>>
>> LFPs don't like to be charged while cold (below the freezing point of water is the rule of thumb, even though they are not made of water). But they discharge just fine while (reasonably) cold. Their capacity while cold doesn't suffer anything like the way SLAs capacity does.
>
> FYI the capacity does still suffer somewhat, -20% at -10c, http://liionbms.com/pdf/kokam/SLPB100216216H_40Ah%20Nano.pdf
>

You grabbed the data sheet for a lithium-polymer battery, which is quite
different than the LFP that John would have been using.

http://kokam.com/data/Kokam_Cell_Brochure_V.1.pdf?PHPSESSID=127ce197928d 82d81619847c0b83f2f5

Even with the correct data sheet, that would have been for a brand new
battery, no cell balancing issues.

kinsell

June 2nd 20, 05:46 AM

On 5/25/20 9:47 PM, Eric Greenwell wrote:
> 2G wrote on 5/25/2020 2:20 PM:
>> On Wednesday, May 13, 2020 at 8:00:09 PM UTC-7, kinsell wrote:
> ...
>>>>
>>>> The BMS in all LFPs may not have the same functionality regarding
>>>> balancing but at the very least they should start/stop accepting
>>>> charge appropriately.
>>>>
>>>
>>> It matters not what you think should happen, the truth is not all LFP
>>> batteries have a BMS, and of those that do, not all of them protect from
>>> over and under voltage.
>>
>> Which LFP batteries don't have a BMS?
>>
>> Tom
>
> The "powersports" (ie, for engine starting) LFP don't always have a BMS.
> A motorglider pilot might be tempted to use one for the engine, for
> example.
>

StarkPower had a series of batteries aimed at motorcycles that they were
quite open about not having a BMS. Unfortunately they're in Chapter 7
now and the website is gone.

More commonly, some batteries with BMS don't have over and under voltage
protection. Richard Pfiffner one time was testing batteries, and his
vendor shipped 24 volt chargers accidentally for 12 volt batteries. All
the white stuff leaked out of the battery. Some electrical genius on
R.A.S. (don't remember which one) declared that they really had
overvoltage protection, but 24 volts just wasn't enough to trigger it.

One of our fellow Schleicher motorglider pilots had an LFP, left the
transponder on, and ruined the battery. A 15-20 AH battery intended as
a starter battery can easily find it's way into other applications. You
may have read about the ASG 32 mi that got fried when the solar
controller malfunctioned, drained the battery, and got quite hot when
charged from another charger. Did it have a BMS? Doesn't really matter.

Dave

June 2nd 20, 03:40 PM

On Monday, June 1, 2020 at 9:46:09 PM UTC-7, kinsell wrote:
> On 5/25/20 9:47 PM, Eric Greenwell wrote:
> > 2G wrote on 5/25/2020 2:20 PM:
> >> On Wednesday, May 13, 2020 at 8:00:09 PM UTC-7, kinsell wrote:
> > ...
> >>>>
> >>>> The BMS in all LFPs may not have the same functionality regarding
> >>>> balancing but at the very least they should start/stop accepting
> >>>> charge appropriately.
> >>>>
> >>>
> >>> It matters not what you think should happen, the truth is not all LFP
> >>> batteries have a BMS, and of those that do, not all of them protect from
> >>> over and under voltage.
> >>
> >> Which LFP batteries don't have a BMS?
> >>
> >> Tom
> >
> > The "powersports" (ie, for engine starting) LFP don't always have a BMS.
> > A motorglider pilot might be tempted to use one for the engine, for
> > example.
> >
>
> StarkPower had a series of batteries aimed at motorcycles that they were
> quite open about not having a BMS. Unfortunately they're in Chapter 7
> now and the website is gone.
>
> More commonly, some batteries with BMS don't have over and under voltage
> protection. Richard Pfiffner one time was testing batteries, and his
> vendor shipped 24 volt chargers accidentally for 12 volt batteries. All
> the white stuff leaked out of the battery. Some electrical genius on
> R.A.S. (don't remember which one) declared that they really had
> overvoltage protection, but 24 volts just wasn't enough to trigger it.
>
> One of our fellow Schleicher motorglider pilots had an LFP, left the
> transponder on, and ruined the battery. A 15-20 AH battery intended as
> a starter battery can easily find it's way into other applications. You
> may have read about the ASG 32 mi that got fried when the solar
> controller malfunctioned, drained the battery, and got quite hot when
> charged from another charger. Did it have a BMS? Doesn't really matter.
>
> Dave

I think it matters: what kind of battery was it?

Tom

Richard Pfiffner[_2_]

June 2nd 20, 05:26 PM

On Monday, June 1, 2020 at 9:46:09 PM UTC-7, kinsell wrote:
> On 5/25/20 9:47 PM, Eric Greenwell wrote:
> > 2G wrote on 5/25/2020 2:20 PM:
> >> On Wednesday, May 13, 2020 at 8:00:09 PM UTC-7, kinsell wrote:
> > ...
> >>>>
> >>>> The BMS in all LFPs may not have the same functionality regarding
> >>>> balancing but at the very least they should start/stop accepting
> >>>> charge appropriately.
> >>>>
> >>>
> >>> It matters not what you think should happen, the truth is not all LFP
> >>> batteries have a BMS, and of those that do, not all of them protect from
> >>> over and under voltage.
> >>
> >> Which LFP batteries don't have a BMS?
> >>
> >> Tom
> >
> > The "powersports" (ie, for engine starting) LFP don't always have a BMS.
> > A motorglider pilot might be tempted to use one for the engine, for
> > example.
> >
>
> StarkPower had a series of batteries aimed at motorcycles that they were
> quite open about not having a BMS. Unfortunately they're in Chapter 7
> now and the website is gone.
>
> More commonly, some batteries with BMS don't have over and under voltage
> protection. Richard Pfiffner one time was testing batteries, and his
> vendor shipped 24 volt chargers accidentally for 12 volt batteries. All
> the white stuff leaked out of the battery. Some electrical genius on
> R.A.S. (don't remember which one) declared that they really had
> overvoltage protection, but 24 volts just wasn't enough to trigger it.
>
> One of our fellow Schleicher motorglider pilots had an LFP, left the
> transponder on, and ruined the battery. A 15-20 AH battery intended as
> a starter battery can easily find it's way into other applications. You
> may have read about the ASG 32 mi that got fried when the solar
> controller malfunctioned, drained the battery, and got quite hot when
> charged from another charger. Did it have a BMS? Doesn't really matter.
>
> Dave

The problem batteries were Bioenno Batteries.

Richard

Eric Greenwell[_4_]

June 2nd 20, 06:09 PM

Richard Pfiffner wrote on 6/2/2020 9:26 AM:
....
>>>
>>
>> StarkPower had a series of batteries aimed at motorcycles that they were
>> quite open about not having a BMS. Unfortunately they're in Chapter 7
>> now and the website is gone.
>>
>> More commonly, some batteries with BMS don't have over and under voltage
>> protection. Richard Pfiffner one time was testing batteries, and his
>> vendor shipped 24 volt chargers accidentally for 12 volt batteries. All
>> the white stuff leaked out of the battery. Some electrical genius on
>> R.A.S. (don't remember which one) declared that they really had
>> overvoltage protection, but 24 volts just wasn't enough to trigger it.
>>
>> One of our fellow Schleicher motorglider pilots had an LFP, left the
>> transponder on, and ruined the battery. A 15-20 AH battery intended as
>> a starter battery can easily find it's way into other applications. You
>> may have read about the ASG 32 mi that got fried when the solar
>> controller malfunctioned, drained the battery, and got quite hot when
>> charged from another charger. Did it have a BMS? Doesn't really matter.
>>
>> Dave
>
> The problem batteries were Bioenno Batteries.

Were they Bioennos with a BMS that protects against overvoltage? For example, I
use the BLF-1220AS, which ....

"Includes built-in PCM (protection circuit module) which provides internal cell
balancing and management, protection from overcurrent, undervoltage
(overdischarge), overvoltage and short circuiting, and has integrated charging
circuitry "

I haven't tried applying 24 volts to it, but I'd expect it to protect against 24
VDC being applied to it. I've just emailed Bioenno this question, but have not
heard back.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorgliders/publications/download-the-guide-1

Dan Marotta

June 2nd 20, 07:10 PM

My Bioenno batteries worked just fine for several years.Â* Just sayin'...

On 6/2/2020 10:26 AM, Richard Pfiffner wrote:
> On Monday, June 1, 2020 at 9:46:09 PM UTC-7, kinsell wrote:
>> On 5/25/20 9:47 PM, Eric Greenwell wrote:
>>> 2G wrote on 5/25/2020 2:20 PM:
>>>> On Wednesday, May 13, 2020 at 8:00:09 PM UTC-7, kinsell wrote:
>>> ...
>>>>>> The BMS in all LFPs may not have the same functionality regarding
>>>>>> balancing but at the very least they should start/stop accepting
>>>>>> charge appropriately.
>>>>>>
>>>>> It matters not what you think should happen, the truth is not all LFP
>>>>> batteries have a BMS, and of those that do, not all of them protect from
>>>>> over and under voltage.
>>>> Which LFP batteries don't have a BMS?
>>>>
>>>> Tom
>>> The "powersports" (ie, for engine starting) LFP don't always have a BMS.
>>> A motorglider pilot might be tempted to use one for the engine, for
>>> example.
>>>
>> StarkPower had a series of batteries aimed at motorcycles that they were
>> quite open about not having a BMS. Unfortunately they're in Chapter 7
>> now and the website is gone.
>>
>> More commonly, some batteries with BMS don't have over and under voltage
>> protection. Richard Pfiffner one time was testing batteries, and his
>> vendor shipped 24 volt chargers accidentally for 12 volt batteries. All
>> the white stuff leaked out of the battery. Some electrical genius on
>> R.A.S. (don't remember which one) declared that they really had
>> overvoltage protection, but 24 volts just wasn't enough to trigger it.
>>
>> One of our fellow Schleicher motorglider pilots had an LFP, left the
>> transponder on, and ruined the battery. A 15-20 AH battery intended as
>> a starter battery can easily find it's way into other applications. You
>> may have read about the ASG 32 mi that got fried when the solar
>> controller malfunctioned, drained the battery, and got quite hot when
>> charged from another charger. Did it have a BMS? Doesn't really matter.
>>
>> Dave
> The problem batteries were Bioenno Batteries.
>
> Richard

--
Dan, 5J

[email protected]

June 2nd 20, 08:52 PM

On Tuesday, June 2, 2020 at 2:10:54 PM UTC-4, Dan Marotta wrote:
> My Bioenno batteries worked just fine for several years.Â* Just sayin'...
>
> On 6/2/2020 10:26 AM, Richard Pfiffner wrote:
> > On Monday, June 1, 2020 at 9:46:09 PM UTC-7, kinsell wrote:
> >> On 5/25/20 9:47 PM, Eric Greenwell wrote:
> >>> 2G wrote on 5/25/2020 2:20 PM:
> >>>> On Wednesday, May 13, 2020 at 8:00:09 PM UTC-7, kinsell wrote:
> >>> ...
> >>>>>> The BMS in all LFPs may not have the same functionality regarding
> >>>>>> balancing but at the very least they should start/stop accepting
> >>>>>> charge appropriately.
> >>>>>>
> >>>>> It matters not what you think should happen, the truth is not all LFP
> >>>>> batteries have a BMS, and of those that do, not all of them protect from
> >>>>> over and under voltage.
> >>>> Which LFP batteries don't have a BMS?
> >>>>
> >>>> Tom
> >>> The "powersports" (ie, for engine starting) LFP don't always have a BMS.
> >>> A motorglider pilot might be tempted to use one for the engine, for
> >>> example.
> >>>
> >> StarkPower had a series of batteries aimed at motorcycles that they were
> >> quite open about not having a BMS. Unfortunately they're in Chapter 7
> >> now and the website is gone.
> >>
> >> More commonly, some batteries with BMS don't have over and under voltage
> >> protection. Richard Pfiffner one time was testing batteries, and his
> >> vendor shipped 24 volt chargers accidentally for 12 volt batteries. All
> >> the white stuff leaked out of the battery. Some electrical genius on
> >> R.A.S. (don't remember which one) declared that they really had
> >> overvoltage protection, but 24 volts just wasn't enough to trigger it.
> >>
> >> One of our fellow Schleicher motorglider pilots had an LFP, left the
> >> transponder on, and ruined the battery. A 15-20 AH battery intended as
> >> a starter battery can easily find it's way into other applications. You
> >> may have read about the ASG 32 mi that got fried when the solar
> >> controller malfunctioned, drained the battery, and got quite hot when
> >> charged from another charger. Did it have a BMS? Doesn't really matter.
> >>
> >> Dave
> > The problem batteries were Bioenno Batteries.
> >
> > Richard
>
> --
> Dan, 5J

The BMS boards must be changing over the years. I don't expect a company like Bioenno could keep getting the same model BMS over time, even if they tried. Not at a reasonable price anyway. You just get whatever is being churned out in large numbers by a few Chinese factories at the moment. If you want to know whether your specific battery has overvoltage cutoff, try it! Connect to a source with about 15-18 volts, via a resistor to limit the current, and watch the voltage on the battery. It should eventually drop (when cut off at something less than 15V if it's a "12V" LFP), and then the voltage on the resistor should drop to zero (no current). A smart charger such as the iMax B6 can serve for the test, tell it the battery has 5 LFP cells in series ("15V" battery), limit the current to 0.1A, and watch what happens.

Last year I bought an "energized outside" brand (since renamed) LFP battery.. When I charge it with my B6 smart charger, the BMS cuts out at about 14.4V, a bit earlier than the B6 would stop the charge at about 14.6V. As a result, the B6 yells at me about the battery being disconnected, and I can't see what the total amphours charge was. Minor annoyance. At least I know that that battery has a high-voltage cutoff.

And another LFP battery I recently bought, PowerSync brand, shuts itself off when it tries to start up the motor in an electric mower I am using it in.. (Actually two 12V batteries in series.) The initial current surge is somewhat over the 20 amps peak that this battery allows. I solved that problem by adding a longish spool of wire in series with the motor to serve as extra resistance (0.3 ohms) to limit that current surge. And now I know that that BMS really does have an over-current shut-off.

MNLou

June 3rd 20, 04:02 AM

On Tuesday, June 2, 2020 at 1:10:54 PM UTC-5, Dan Marotta wrote:
> My Bioenno batteries worked just fine for several years.Â* Just sayin'...

I'm with Dan. I'm running Bioenno batteries and am very happy with them. 2 are 4 years old and work like new.

YMMV -

Lou

Richard Pfiffner[_2_]

June 3rd 20, 01:35 PM

On Tuesday, June 2, 2020 at 10:09:21 AM UTC-7, Eric Greenwell wrote:
> Richard Pfiffner wrote on 6/2/2020 9:26 AM:
> ...
> >>>
> >>
> >> StarkPower had a series of batteries aimed at motorcycles that they were
> >> quite open about not having a BMS. Unfortunately they're in Chapter 7
> >> now and the website is gone.
> >>
> >> More commonly, some batteries with BMS don't have over and under voltage
> >> protection. Richard Pfiffner one time was testing batteries, and his
> >> vendor shipped 24 volt chargers accidentally for 12 volt batteries. All
> >> the white stuff leaked out of the battery. Some electrical genius on
> >> R.A.S. (don't remember which one) declared that they really had
> >> overvoltage protection, but 24 volts just wasn't enough to trigger it.
> >>
> >> One of our fellow Schleicher motorglider pilots had an LFP, left the
> >> transponder on, and ruined the battery. A 15-20 AH battery intended as
> >> a starter battery can easily find it's way into other applications. You
> >> may have read about the ASG 32 mi that got fried when the solar
> >> controller malfunctioned, drained the battery, and got quite hot when
> >> charged from another charger. Did it have a BMS? Doesn't really matter.
> >>
> >> Dave
> >
> > The problem batteries were Bioenno Batteries.
>
> Were they Bioennos with a BMS that protects against overvoltage? For example, I
> use the BLF-1220AS, which ....
>
> "Includes built-in PCM (protection circuit module) which provides internal cell
> balancing and management, protection from overcurrent, undervoltage
> (overdischarge), overvoltage and short circuiting, and has integrated charging
> circuitry "
>
> I haven't tried applying 24 volts to it, but I'd expect it to protect against 24
> VDC being applied to it. I've just emailed Bioenno this question, but have not
> heard back.
>
> --
> Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
> - "A Guide to Self-Launching Sailplane Operation"
> https://sites.google.com/site/motorgliders/publications/download-the-guide-1

Eric,

I don't know about the BMS. All I know is Bioenno supplied the batteries with a 24 volt charger. When the batteries were charged they were destroyed. Bioenno replaced the batteries and chargers although it took a long time to get the replacements.

Richard

Eric Greenwell[_4_]

June 3rd 20, 02:11 PM

Richard Pfiffner wrote on 6/3/2020 5:35 AM:
> On Tuesday, June 2, 2020 at 10:09:21 AM UTC-7, Eric Greenwell wrote:
>> Richard Pfiffner wrote on 6/2/2020 9:26 AM:
>> ...
>>>>>
>>>>
>>>> StarkPower had a series of batteries aimed at motorcycles that they were
>>>> quite open about not having a BMS. Unfortunately they're in Chapter 7
>>>> now and the website is gone.
>>>>
>>>> More commonly, some batteries with BMS don't have over and under voltage
>>>> protection. Richard Pfiffner one time was testing batteries, and his
>>>> vendor shipped 24 volt chargers accidentally for 12 volt batteries. All
>>>> the white stuff leaked out of the battery. Some electrical genius on
>>>> R.A.S. (don't remember which one) declared that they really had
>>>> overvoltage protection, but 24 volts just wasn't enough to trigger it.
>>>>
>>>> One of our fellow Schleicher motorglider pilots had an LFP, left the
>>>> transponder on, and ruined the battery. A 15-20 AH battery intended as
>>>> a starter battery can easily find it's way into other applications. You
>>>> may have read about the ASG 32 mi that got fried when the solar
>>>> controller malfunctioned, drained the battery, and got quite hot when
>>>> charged from another charger. Did it have a BMS? Doesn't really matter.
>>>>
>>>> Dave
>>>
>>> The problem batteries were Bioenno Batteries.
>>
>> Were they Bioennos with a BMS that protects against overvoltage? For example, I
>> use the BLF-1220AS, which ....
>>
>> "Includes built-in PCM (protection circuit module) which provides internal cell
>> balancing and management, protection from overcurrent, undervoltage
>> (overdischarge), overvoltage and short circuiting, and has integrated charging
>> circuitry "
>>
>> I haven't tried applying 24 volts to it, but I'd expect it to protect against 24
>> VDC being applied to it. I've just emailed Bioenno this question, but have not
>> heard back.
>
> Eric,
>
> I don't know about the BMS. All I know is Bioenno supplied the batteries with a 24 volt charger. When the batteries were charged they were destroyed. Bioenno replaced the batteries and chargers although it took a long time to get the replacements.
>
> Richard
>
I emailed this question to Bioenno:

"Does the BLF-1220AS protect itself if a charger for a 24 volt Bioenno is
connected to it?"

Their answer:

"The BLF-1220AS can only accept a charging voltage from 13.8VDC to 15.3VDC. If
you exceed 15.3VDC, the BMS will trip and the battery shuts off. However, high
voltage should not be left attached continuously to the battery which can cause
permanent damage to the BMS/cells. If the voltage is less than 13.8VDC, the
battery will charge, but not be 100% charged.

-Kevin"

I don't consider 24 volts (or the likely charging voltage of 28 volts) to be a
"high voltage", but it sounds like leaving a 24 volt charger applied to a 12 volt
Bioenno battery will damage the battery after a while. So, while the battery does
protect itself in the short term, neither the battery nor the charger indicate
that there is a problem. Since the battery can be hidden from view, I think the
charger should be smart enough to indicate it's been connected to the wrong
battery AND it should disconnect itself. The Bioenno charger does neither,
unfortunately.

If you do connect the 24 volt charger to the 12 volt battery, the LED indicator
(all it has) will show GREEN, indicating the battery is fully charged, instead of
RED, your expectation to indicate it is charging. Too subtle, I think.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorgliders/publications/download-the-guide-1

[email protected]

June 3rd 20, 08:06 PM

On Wednesday, June 3, 2020 at 9:12:00 AM UTC-4, Eric Greenwell wrote:
> Richard Pfiffner wrote on 6/3/2020 5:35 AM:
> > On Tuesday, June 2, 2020 at 10:09:21 AM UTC-7, Eric Greenwell wrote:
> >> Richard Pfiffner wrote on 6/2/2020 9:26 AM:
> >> ...
> >>>>>
> >>>>
> >>>> StarkPower had a series of batteries aimed at motorcycles that they were
> >>>> quite open about not having a BMS. Unfortunately they're in Chapter 7
> >>>> now and the website is gone.
> >>>>
> >>>> More commonly, some batteries with BMS don't have over and under voltage
> >>>> protection. Richard Pfiffner one time was testing batteries, and his
> >>>> vendor shipped 24 volt chargers accidentally for 12 volt batteries. All
> >>>> the white stuff leaked out of the battery. Some electrical genius on
> >>>> R.A.S. (don't remember which one) declared that they really had
> >>>> overvoltage protection, but 24 volts just wasn't enough to trigger it.

Eric Greenwell[_4_]

June 3rd 20, 09:12 PM

wrote on 6/3/2020 12:06 PM:
> On Wednesday, June 3, 2020 at 9:12:00 AM UTC-4, Eric Greenwell wrote:
>> Richard Pfiffner wrote on 6/3/2020 5:35 AM:
>>> On Tuesday, June 2, 2020 at 10:09:21 AM UTC-7, Eric Greenwell wrote:
>>>> Richard Pfiffner wrote on 6/2/2020 9:26 AM:
>>>> ...
>>>>>>>
>>>>>>
>>>>>> StarkPower had a series of batteries aimed at motorcycles that they were
>>>>>> quite open about not having a BMS. Unfortunately they're in Chapter 7
>>>>>> now and the website is gone.
>>>>>>
>>>>>> More commonly, some batteries with BMS don't have over and under voltage
>>>>>> protection. Richard Pfiffner one time was testing batteries, and his
>>>>>> vendor shipped 24 volt chargers accidentally for 12 volt batteries. All
>>>>>> the white stuff leaked out of the battery. Some electrical genius on
>>>>>> R.A.S. (don't remember which one) declared that they really had
>>>>>> overvoltage protection, but 24 volts just wasn't enough to trigger it.
>>>>>>
>>>>>> One of our fellow Schleicher motorglider pilots had an LFP, left the
>>>>>> transponder on, and ruined the battery. A 15-20 AH battery intended as
>>>>>> a starter battery can easily find it's way into other applications. You
>>>>>> may have read about the ASG 32 mi that got fried when the solar
>>>>>> controller malfunctioned, drained the battery, and got quite hot when
>>>>>> charged from another charger. Did it have a BMS? Doesn't really matter.
>>>>>>
>>>>>> Dave
>>>>>
>>>>> The problem batteries were Bioenno Batteries.
>>>>
>>>> Were they Bioennos with a BMS that protects against overvoltage? For example, I
>>>> use the BLF-1220AS, which ....
>>>>
>>>> "Includes built-in PCM (protection circuit module) which provides internal cell
>>>> balancing and management, protection from overcurrent, undervoltage
>>>> (overdischarge), overvoltage and short circuiting, and has integrated charging
>>>> circuitry "
>>>>
>>>> I haven't tried applying 24 volts to it, but I'd expect it to protect against 24
>>>> VDC being applied to it. I've just emailed Bioenno this question, but have not
>>>> heard back.
>>>
>>> Eric,
>>>
>>> I don't know about the BMS. All I know is Bioenno supplied the batteries with a 24 volt charger. When the batteries were charged they were destroyed. Bioenno replaced the batteries and chargers although it took a long time to get the replacements.
>>>
>>> Richard
>>>
>> I emailed this question to Bioenno:
>>
>> "Does the BLF-1220AS protect itself if a charger for a 24 volt Bioenno is
>> connected to it?"
>>
>> Their answer:
>>
>> "The BLF-1220AS can only accept a charging voltage from 13.8VDC to 15.3VDC. If
>> you exceed 15.3VDC, the BMS will trip and the battery shuts off. However, high
>> voltage should not be left attached continuously to the battery which can cause
>> permanent damage to the BMS/cells. If the voltage is less than 13.8VDC, the
>> battery will charge, but not be 100% charged.
>>
>> -Kevin"
>>
>> I don't consider 24 volts (or the likely charging voltage of 28 volts) to be a
>> "high voltage", but it sounds like leaving a 24 volt charger applied to a 12 volt
>> Bioenno battery will damage the battery after a while. So, while the battery does
>> protect itself in the short term, neither the battery nor the charger indicate
>> that there is a problem. Since the battery can be hidden from view, I think the
>> charger should be smart enough to indicate it's been connected to the wrong
>> battery AND it should disconnect itself. The Bioenno charger does neither,
>> unfortunately.
>>
>> If you do connect the 24 volt charger to the 12 volt battery, the LED indicator
>> (all it has) will show GREEN, indicating the battery is fully charged, instead of
>> RED, your expectation to indicate it is charging. Too subtle, I think.
>>
>> --
>> Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
>> - "A Guide to Self-Launching Sailplane Operation"
>> https://sites.google.com/site/motorgliders/publications/download-the-guide-1
>
> The battery does not "know" that it is connected to a 24V charger. The battery itself should clamp the voltage to a value consistent with it's state-of-charge. If a 24V charger is able to deliver current at the relatively low voltage of the 12V battery, then current will flow and the battery will absorb this current, charge, and reach the BMS cutoff voltage at which time the overcharge protection FET should open. The voltage across the battery terminals will then be 24V but with no current flow since the FET is open. The internal battery cell cluster will not "see" this high voltage but portions of the BMS circuit will. This 24V "may" damage the BMS if it is not rated for it. There may be some small leakage current through the overcharge FET which may get through to the inner cell cluster which, over a (very, very) long period of time, damage the cells.
>
> Danny Brotto
>
Perhaps I wasn't clear. I want to the battery to have an LED indicator that
announces it has shut off the battery due to an overvoltage. And definitely shut
off - not clamp the voltage. It doesn't matter what is supplying the high voltage.

I also want the 24 volt battery charger to shut off it's output if it doesn't
detect a 24 volt battery on it's output, and have an LED indicator to show that's
why it shut off. I very much do not want a 24 volt charger to attempt charging
anything but a 24 volt battery.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorgliders/publications/download-the-guide-1

[email protected]

June 3rd 20, 09:50 PM

I have recently moved from my still good, 8 year old K2 to the rated 9 amp version of these PowerSonic Iron Phosphate batteries:

https://www.power-sonic.com/batteries/lithium-bluetooth-series/

I am very happy with it so far. My tester shows that at a 1 amp discharge rate I'm getting 10.3 Amp Hours. The battery has over/under voltage protection although I have not tested the feature. The app (Android only) is very useful providing SOC, voltage, current measurement in/out, number of discharge cycles, individual cell voltage readings, and battery use event errors (over/under voltage, etc.) It works great. I am able to insure that starting the flight I'm at 100% SOC (well, 99% because I know that my charger slightly undercharges.) After 5 hours of use I'm down to 60% very consistently. The Bluetooth system is TI-based and I believe that the BMU is also TI-based. It is a tremendous value for what you get.

Danny Brotto

kinsell

June 3rd 20, 11:19 PM

On 6/3/20 2:12 PM, Eric Greenwell wrote:
> wrote on 6/3/2020 12:06 PM:
>> On Wednesday, June 3, 2020 at 9:12:00 AM UTC-4, Eric Greenwell wrote:
>>> Richard Pfiffner wrote on 6/3/2020 5:35 AM:
>>>> On Tuesday, June 2, 2020 at 10:09:21 AM UTC-7, Eric Greenwell wrote:
>>>>> Richard Pfiffner wrote on 6/2/2020 9:26 AM:
>>>>> ...
>>>>>>>>
>>>>>>>
>>>>>>> StarkPower had a series of batteries aimed at motorcycles that
>>>>>>> they were
>>>>>>> quite open about not having a BMS.Â* Unfortunately they're in
>>>>>>> Chapter 7
>>>>>>> now and the website is gone.
>>>>>>>
>>>>>>> More commonly, some batteries with BMS don't have over and under
>>>>>>> voltage
>>>>>>> protection.Â* Richard Pfiffner one time was testing batteries, and
>>>>>>> his
>>>>>>> vendor shipped 24 volt chargers accidentally for 12 volt
>>>>>>> batteries.Â* All
>>>>>>> the white stuff leaked out of the battery.Â* Some electrical
>>>>>>> genius on
>>>>>>> R.A.S. (don't remember which one) declared that they really had
>>>>>>> overvoltage protection, but 24 volts just wasn't enough to
>>>>>>> trigger it.
>>>>>>>
>>>>>>> One of our fellow Schleicher motorglider pilots had an LFP, left the
>>>>>>> transponder on, and ruined the battery.Â* A 15-20 AH battery
>>>>>>> intended as
>>>>>>> a starter battery can easily find it's way into other
>>>>>>> applications.Â* You
>>>>>>> may have read about the ASG 32 mi that got fried when the solar
>>>>>>> controller malfunctioned, drained the battery, and got quite hot
>>>>>>> when
>>>>>>> charged from another charger.Â* Did it have a BMS?Â* Doesn't really
>>>>>>> matter.
>>>>>>>
>>>>>>> Dave
>>>>>>
>>>>>> The problem batteries were Bioenno Batteries.
>>>>>
>>>>> Were they Bioennos with a BMS that protects against overvoltage?
>>>>> For example, I
>>>>> use the BLF-1220AS, which ....
>>>>>
>>>>> "Includes built-in PCM (protection circuit module) which provides
>>>>> internal cell
>>>>> balancing and management, protection from overcurrent, undervoltage
>>>>> (overdischarge), overvoltage and short circuiting, and has
>>>>> integrated charging
>>>>> circuitry "
>>>>>
>>>>> I haven't tried applying 24 volts to it, but I'd expect it to
>>>>> protect against 24
>>>>> VDC being applied to it. I've just emailed Bioenno this question,
>>>>> but have not
>>>>> heard back.
>>>>
>>>> Eric,
>>>>
>>>> I don't know about the BMS.Â* All I know is Bioenno supplied the
>>>> batteries with a 24 volt charger. When the batteries were charged
>>>> they were destroyed.Â* Bioenno replaced the batteries and chargers
>>>> although it took a long time to get the replacements.
>>>>
>>>> Richard
>>>>
>>> I emailed this question to Bioenno:
>>>
>>> "Does the BLF-1220AS protect itself if a charger for a 24 volt
>>> Bioenno is
>>> connected to it?"
>>>
>>> Their answer:
>>>
>>> "The BLF-1220AS can only accept a charging voltage from 13.8VDC to
>>> 15.3VDC.Â* If
>>> you exceed 15.3VDC, the BMS will trip and the battery shuts off.
>>> However, high
>>> voltage should not be left attached continuously to the battery which
>>> can cause
>>> permanent damage to the BMS/cells.Â* If the voltage is less than
>>> 13.8VDC, the
>>> battery will charge, but not be 100% charged.
>>>
>>> -Kevin"
>>>
>>> I don't consider 24 volts (or the likely charging voltage of 28
>>> volts) to be a
>>> "high voltage", but it sounds like leaving a 24 volt charger applied
>>> to a 12 volt
>>> Bioenno battery will damage the battery after a while. So, while the
>>> battery does
>>> protect itself in the short term, neither the battery nor the charger
>>> indicate
>>> that there is a problem. Since the battery can be hidden from view, I
>>> think the
>>> charger should be smart enough to indicate it's been connected to the
>>> wrong
>>> battery AND it should disconnect itself. The Bioenno charger does
>>> neither,
>>> unfortunately.
>>>
>>> If you do connect the 24 volt charger to the 12 volt battery, the LED
>>> indicator
>>> (all it has) will show GREEN, indicating the battery is fully
>>> charged, instead of
>>> RED, your expectation to indicate it is charging. Too subtle, I think.
>>>
>>> --
>>> Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
>>> email me)
>>> - "A Guide to Self-Launching Sailplane Operation"
>>>
>>> https://sites.google.com/site/motorgliders/publications/download-the-guide-1
>>>
>>
>> The battery does not "know" that it is connected to a 24V charger. The
>> battery itself should clamp the voltage to a value consistent with
>> it's state-of-charge. If a 24V charger is able to deliver current at
>> the relatively low voltage of the 12V battery, then current will flow
>> and the battery will absorb this current, charge, and reach the BMS
>> cutoff voltage at which time the overcharge protection FET should
>> open. The voltage across the battery terminals will then be 24V but
>> with no current flow since the FET is open. The internal battery cell
>> cluster will not "see" this high voltage but portions of the BMS
>> circuit will. This 24V "may" damage the BMS if it is not rated for it.
>> There may be some small leakage current through the overcharge FET
>> which may get through to the inner cell cluster which, over a (very,
>> very) long period of time, damage the cells.
>>
>> Danny Brotto
>>
> Perhaps I wasn't clear. I want to the battery to have an LED indicator
> that announces it has shut off the battery due to an overvoltage. And
> definitely shut off - not clamp the voltage. It doesn't matter what is
> supplying the high voltage.
>
> I also want the 24 volt battery charger to shut off it's output if it
> doesn't detect a 24 volt battery on it's output, and have an LED
> indicator to show that's why it shut off. I very much do not want a 24
> volt charger to attempt charging anything but a 24 volt battery.
>

My first priority would be to have an overvoltage circuit that performs
as you would reasonably expect it to, along with clear specs such as
"withstands 50 volt continuous voltage on the terminals with no damage"
and "withstands 20 volt reverse voltage on the terminals". Many smart
chargers will refuse to try to charge a backwards connected battery, but
not all of them.

EaarthX makes LFP's for experimental and certified aircraft, and they do
have an error output that drives an LED and/or an EFIS system to warn of
problems like a weak cell. They require that this info be provided to
the pilot in flight.

I was a little confused by Danny's answer, he seems to be confusing how
he thinks the Bioenno batteries should work, rather than how they
actually DO work. This after the vendor confirmed they can't withstand
continuous overvoltage, and Richard dramatically demonstrated the
problem on a number of units. Fortunately Richard does 100% incoming
inspection on his batteries, and was able to catch the issue. Doesn't
speak well to the vendor's quality control. Maybe not as bad as
sprinkling metal shavings in the lithium-cobalt batteries, but still not
good.

-Dave

[email protected]

June 4th 20, 12:24 AM

Dave,

The Bioenno site shows this 14.6V 2A charger to be the one recommended on their web site. I suspect the supplied 24V chargers were a QC issue in pack out; somebody packed 24V chargers with 12V batteries. Bioenno also sells 24V packs with a compatable charger.

https://www.bioennopower.com/collections/8-ac-to-dc-chargers-accessories/products/14-6vdc-2a-lifepo4-ac-to-dc-charger

Danny Brotto

Dan Marotta

June 4th 20, 01:28 AM

I have one of THESE
<https://smile.amazon.com/gp/product/B004LWTHP2/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1>
which I used on the C-180 (24v system) and on anything else in the
hangar (12v systems).Â* If it's been on the 180 and is set for 24 volts
and I connect it to a 12 volt battery, the lights flash wildly to tell
me there's a problem.Â* Then I simply set it for 12v with the push of a
button.

On 6/3/2020 2:12 PM, Eric Greenwell wrote:
> wrote on 6/3/2020 12:06 PM:
>> On Wednesday, June 3, 2020 at 9:12:00 AM UTC-4, Eric Greenwell wrote:
>>> Richard Pfiffner wrote on 6/3/2020 5:35 AM:
>>>> On Tuesday, June 2, 2020 at 10:09:21 AM UTC-7, Eric Greenwell wrote:
>>>>> Richard Pfiffner wrote on 6/2/2020 9:26 AM:
>>>>> ...
>>>>>>>>
>>>>>>>
>>>>>>> StarkPower had a series of batteries aimed at motorcycles that
>>>>>>> they were
>>>>>>> quite open about not having a BMS.Â* Unfortunately they're in
>>>>>>> Chapter 7
>>>>>>> now and the website is gone.
>>>>>>>
>>>>>>> More commonly, some batteries with BMS don't have over and under
>>>>>>> voltage
>>>>>>> protection.Â* Richard Pfiffner one time was testing batteries,
>>>>>>> and his
>>>>>>> vendor shipped 24 volt chargers accidentally for 12 volt
>>>>>>> batteries.Â* All
>>>>>>> the white stuff leaked out of the battery.Â* Some electrical
>>>>>>> genius on
>>>>>>> R.A.S. (don't remember which one) declared that they really had
>>>>>>> overvoltage protection, but 24 volts just wasn't enough to
>>>>>>> trigger it.
>>>>>>>
>>>>>>> One of our fellow Schleicher motorglider pilots had an LFP, left
>>>>>>> the
>>>>>>> transponder on, and ruined the battery.Â* A 15-20 AH battery
>>>>>>> intended as
>>>>>>> a starter battery can easily find it's way into other
>>>>>>> applications.Â* You
>>>>>>> may have read about the ASG 32 mi that got fried when the solar
>>>>>>> controller malfunctioned, drained the battery, and got quite hot
>>>>>>> when
>>>>>>> charged from another charger.Â* Did it have a BMS? Doesn't really
>>>>>>> matter.
>>>>>>>
>>>>>>> Dave
>>>>>>
>>>>>> The problem batteries were Bioenno Batteries.
>>>>>
>>>>> Were they Bioennos with a BMS that protects against overvoltage?
>>>>> For example, I
>>>>> use the BLF-1220AS, which ....
>>>>>
>>>>> "Includes built-in PCM (protection circuit module) which provides
>>>>> internal cell
>>>>> balancing and management, protection from overcurrent, undervoltage
>>>>> (overdischarge), overvoltage and short circuiting, and has
>>>>> integrated charging
>>>>> circuitry "
>>>>>
>>>>> I haven't tried applying 24 volts to it, but I'd expect it to
>>>>> protect against 24
>>>>> VDC being applied to it. I've just emailed Bioenno this question,
>>>>> but have not
>>>>> heard back.
>>>>
>>>> Eric,
>>>>
>>>> I don't know about the BMS.Â* All I know is Bioenno supplied the
>>>> batteries with a 24 volt charger. When the batteries were charged
>>>> they were destroyed.Â* Bioenno replaced the batteries and chargers
>>>> although it took a long time to get the replacements.
>>>>
>>>> Richard
>>>>
>>> I emailed this question to Bioenno:
>>>
>>> "Does the BLF-1220AS protect itself if a charger for a 24 volt
>>> Bioenno is
>>> connected to it?"
>>>
>>> Their answer:
>>>
>>> "The BLF-1220AS can only accept a charging voltage from 13.8VDC to
>>> 15.3VDC.Â* If
>>> you exceed 15.3VDC, the BMS will trip and the battery shuts off.Â*
>>> However, high
>>> voltage should not be left attached continuously to the battery
>>> which can cause
>>> permanent damage to the BMS/cells.Â* If the voltage is less than
>>> 13.8VDC, the
>>> battery will charge, but not be 100% charged.
>>>
>>> -Kevin"
>>>
>>> I don't consider 24 volts (or the likely charging voltage of 28
>>> volts) to be a
>>> "high voltage", but it sounds like leaving a 24 volt charger applied
>>> to a 12 volt
>>> Bioenno battery will damage the battery after a while. So, while the
>>> battery does
>>> protect itself in the short term, neither the battery nor the
>>> charger indicate
>>> that there is a problem. Since the battery can be hidden from view,
>>> I think the
>>> charger should be smart enough to indicate it's been connected to
>>> the wrong
>>> battery AND it should disconnect itself. The Bioenno charger does
>>> neither,
>>> unfortunately.
>>>
>>> If you do connect the 24 volt charger to the 12 volt battery, the
>>> LED indicator
>>> (all it has) will show GREEN, indicating the battery is fully
>>> charged, instead of
>>> RED, your expectation to indicate it is charging. Too subtle, I think.
>>>
>>> --
>>> Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
>>> email me)
>>> - "A Guide to Self-Launching Sailplane Operation"
>>> https://sites.google.com/site/motorgliders/publications/download-the-guide-1
>>
>> The battery does not "know" that it is connected to a 24V charger.
>> The battery itself should clamp the voltage to a value consistent
>> with it's state-of-charge. If a 24V charger is able to deliver
>> current at the relatively low voltage of the 12V battery, then
>> current will flow and the battery will absorb this current, charge,
>> and reach the BMS cutoff voltage at which time the overcharge
>> protection FET should open. The voltage across the battery terminals
>> will then be 24V but with no current flow since the FET is open. The
>> internal battery cell cluster will not "see" this high voltage but
>> portions of the BMS circuit will. This 24V "may" damage the BMS if it
>> is not rated for it. There may be some small leakage current through
>> the overcharge FET which may get through to the inner cell cluster
>> which, over a (very, very) long period of time, damage the cells.
>>
>> Danny Brotto
>>
> Perhaps I wasn't clear. I want to the battery to have an LED indicator
> that announces it has shut off the battery due to an overvoltage. And
> definitely shut off - not clamp the voltage. It doesn't matter what is
> supplying the high voltage.
>
> I also want the 24 volt battery charger to shut off it's output if it
> doesn't detect a 24 volt battery on it's output, and have an LED
> indicator to show that's why it shut off. I very much do not want a 24
> volt charger to attempt charging anything but a 24 volt battery.
>

--
Dan, 5J

kinsell

June 4th 20, 04:48 PM

On 6/2/20 11:09 AM, Eric Greenwell wrote:
> Richard Pfiffner wrote on 6/2/2020 9:26 AM:
> ...
>>>>
>>>
>>> StarkPower had a series of batteries aimed at motorcycles that they were
>>> quite open about not having a BMS.Â* Unfortunately they're in Chapter 7
>>> now and the website is gone.
>>>
>>> More commonly, some batteries with BMS don't have over and under voltage
>>> protection.Â* Richard Pfiffner one time was testing batteries, and his
>>> vendor shipped 24 volt chargers accidentally for 12 volt batteries.Â* All
>>> the white stuff leaked out of the battery.Â* Some electrical genius on
>>> R.A.S. (don't remember which one) declared that they really had
>>> overvoltage protection, but 24 volts just wasn't enough to trigger it.
>>>
>>> One of our fellow Schleicher motorglider pilots had an LFP, left the
>>> transponder on, and ruined the battery.Â* A 15-20 AH battery intended as
>>> a starter battery can easily find it's way into other applications.Â* You
>>> may have read about the ASG 32 mi that got fried when the solar
>>> controller malfunctioned, drained the battery, and got quite hot when
>>> charged from another charger.Â* Did it have a BMS?Â* Doesn't really
>>> matter.
>>>
>>> Dave
>>
>> The problem batteries were Bioenno Batteries.
>
> Were they Bioennos with a BMS that protects against overvoltage? For
> example, I use the BLF-1220AS, which ....
>
> "Includes built-in PCM (protection circuit module) which provides
> internal cell balancing and management, protection from overcurrent,
> undervoltage (overdischarge), overvoltage and short circuiting, and has
> integrated charging circuitry "
>
> I haven't tried applying 24 volts to it, but I'd expect it to protect
> against 24 VDC being applied to it. I've just emailed Bioenno this
> question, but have not heard back.
>

The glossy brochures say they have short-circuit protection, yet the
actual user manual says "Caution do not short circuit negative and
positive terminals" Apparently the BMS circuit isn't as effective as
they like to make it sound.

Reminds me of a story, one of our motorglider friends was telling me
about his new LFP batteries he installed, and said he felt they were
safe due to the BMS. I asked him if he had ever put a wrench across the
terminals to test the short circuit protection. Turns out he hadn't,
and wasn't about to try that. He's the one that had the transponder
left on accidentally, and ruined the battery due to overdischarge just a
few months later. Apparently his BMS circuit wasn't as effective as he
had been lead to believe. I see a pattern here.

John the OP is using two K2 batteries in parallel. The Bioenno manual
says you can do that with theirs, but you should measure the internal
impedance of the batteries and compensate for any difference with
resistors. It warns of the danger of fire, and says to monitor the
batteries continuously. The user is responsible for any problems due to
parallel or series connections. Not exactly a ringing endorsement for
using them in parallel.

https://cdn.shopify.com/s/files/1/0219/0154/files/BLF-1220A_User_Manual_rev_04_23_2019.pdf?209

Would be nice to see what K2 says about that, but they require
registration to see their specs. I'm not saying Bioenno makes a bad
battery, they just seem to be a little more candid than others about the
limitations of their batteries.

-Dave

June 6th 20, 06:06 AM

On Thursday, June 4, 2020 at 8:48:04 AM UTC-7, kinsell wrote:
> On 6/2/20 11:09 AM, Eric Greenwell wrote:
> > Richard Pfiffner wrote on 6/2/2020 9:26 AM:
> > ...
> >>>>
> >>>
> >>> StarkPower had a series of batteries aimed at motorcycles that they were
> >>> quite open about not having a BMS.Â* Unfortunately they're in Chapter 7
> >>> now and the website is gone.
> >>>
> >>> More commonly, some batteries with BMS don't have over and under voltage
> >>> protection.Â* Richard Pfiffner one time was testing batteries, and his
> >>> vendor shipped 24 volt chargers accidentally for 12 volt batteries.Â* All
> >>> the white stuff leaked out of the battery.Â* Some electrical genius on
> >>> R.A.S. (don't remember which one) declared that they really had
> >>> overvoltage protection, but 24 volts just wasn't enough to trigger it..
> >>>
> >>> One of our fellow Schleicher motorglider pilots had an LFP, left the
> >>> transponder on, and ruined the battery.Â* A 15-20 AH battery intended as
> >>> a starter battery can easily find it's way into other applications.Â* You
> >>> may have read about the ASG 32 mi that got fried when the solar
> >>> controller malfunctioned, drained the battery, and got quite hot when
> >>> charged from another charger.Â* Did it have a BMS?Â* Doesn't really
> >>> matter.
> >>>
> >>> Dave
> >>
> >> The problem batteries were Bioenno Batteries.
> >
> > Were they Bioennos with a BMS that protects against overvoltage? For
> > example, I use the BLF-1220AS, which ....
> >
> > "Includes built-in PCM (protection circuit module) which provides
> > internal cell balancing and management, protection from overcurrent,
> > undervoltage (overdischarge), overvoltage and short circuiting, and has
> > integrated charging circuitry "
> >
> > I haven't tried applying 24 volts to it, but I'd expect it to protect
> > against 24 VDC being applied to it. I've just emailed Bioenno this
> > question, but have not heard back.
> >
>
> The glossy brochures say they have short-circuit protection, yet the
> actual user manual says "Caution do not short circuit negative and
> positive terminals" Apparently the BMS circuit isn't as effective as
> they like to make it sound.
>
> Reminds me of a story, one of our motorglider friends was telling me
> about his new LFP batteries he installed, and said he felt they were
> safe due to the BMS. I asked him if he had ever put a wrench across the
> terminals to test the short circuit protection. Turns out he hadn't,
> and wasn't about to try that. He's the one that had the transponder
> left on accidentally, and ruined the battery due to overdischarge just a
> few months later. Apparently his BMS circuit wasn't as effective as he
> had been lead to believe. I see a pattern here.
>
> John the OP is using two K2 batteries in parallel. The Bioenno manual
> says you can do that with theirs, but you should measure the internal
> impedance of the batteries and compensate for any difference with
> resistors. It warns of the danger of fire, and says to monitor the
> batteries continuously. The user is responsible for any problems due to
> parallel or series connections. Not exactly a ringing endorsement for
> using them in parallel.
>
> https://cdn.shopify.com/s/files/1/0219/0154/files/BLF-1220A_User_Manual_rev_04_23_2019.pdf?209
>
> Would be nice to see what K2 says about that, but they require
> registration to see their specs. I'm not saying Bioenno makes a bad
> battery, they just seem to be a little more candid than others about the
> limitations of their batteries.
>
> -Dave

There is one thing about designing in protection against an unintentional short circuit and an entirely another about doing it deliberately. Of course, Bioenno is going to warn against shorting the battery - this can cause serious injury.

Tom