Solar panel controller

[krasw]

Any ideas for Strobl controller replacement? The voltage is not enough for LFP battery. Victron SmartSolar MPPT 75/10 looks good, but according to specs Strobl solar cell voltage is not enough to start the unit (!). Genasun has appalling efficiency.

[Soartech]

On Tuesday, December 29, 2020 at 10:42:19 AM UTC-5, krasw wrote:
> Any ideas for Strobl controller replacement? The voltage is not enough for LFP battery. Victron SmartSolar MPPT 75/10 looks good, but according to specs Strobl solar cell voltage is not enough to start the unit (!). Genasun has appalling efficiency.

We need more info: how many Volts does your cell put out? What is the battery type and size in Watt-hours? What aircraft is this on?

[jfitch]

I'd be amazed if you had room for a Victron in your glider. Both Victron and Genasun make generally good stuff. From the data sheets, the Victron efficiency is "98% peak" and the Genasun is "94 - 99.85% typical". These are effectively the same. What do you find appalling?

On Tuesday, December 29, 2020 at 8:03:58 AM UTC-8, Soartech wrote:
> On Tuesday, December 29, 2020 at 10:42:19 AM UTC-5, krasw wrote:
> > Any ideas for Strobl controller replacement? The voltage is not enough for LFP battery. Victron SmartSolar MPPT 75/10 looks good, but according to specs Strobl solar cell voltage is not enough to start the unit (!). Genasun has appalling efficiency.
> We need more info: how many Volts does your cell put out? What is the battery type and size in Watt-hours? What aircraft is this on?

[krasw]

On Tuesday, 29 December 2020 at 18:52:35 UTC+2, jfitch wrote:
> I'd be amazed if you had room for a Victron in your glider. Both Victron and Genasun make generally good stuff. From the data sheets, the Victron efficiency is "98% peak" and the Genasun is "94 - 99.85% typical". These are effectively the same. What do you find appalling?
> On Tuesday, December 29, 2020 at 8:03:58 AM UTC-8, Soartech wrote:
> > On Tuesday, December 29, 2020 at 10:42:19 AM UTC-5, krasw wrote:
> > > Any ideas for Strobl controller replacement? The voltage is not enough for LFP battery. Victron SmartSolar MPPT 75/10 looks good, but according to specs Strobl solar cell voltage is not enough to start the unit (!). Genasun has appalling efficiency.
> > We need more info: how many Volts does your cell put out? What is the battery type and size in Watt-hours? What aircraft is this on?

Genasun consumes 150mA, six times more than Victron (25 mA). My solar panel produces 550mA (via Strobl controller). Genasun robs almost third of the panel produced power.

[Eric Greenwell[_4_]]

krasw wrote on 12/29/2020 10:36 AM:
> On Tuesday, 29 December 2020 at 18:52:35 UTC+2, jfitch wrote:
>> I'd be amazed if you had room for a Victron in your glider. Both Victron and Genasun make generally good stuff. From the data sheets, the Victron efficiency is "98% peak" and the Genasun is "94 - 99.85% typical". These are effectively the same. What do you find appalling?
>> On Tuesday, December 29, 2020 at 8:03:58 AM UTC-8, Soartech wrote:
>>> On Tuesday, December 29, 2020 at 10:42:19 AM UTC-5, krasw wrote:
>>>> Any ideas for Strobl controller replacement? The voltage is not enough for LFP battery. Victron SmartSolar MPPT 75/10 looks good, but according to specs Strobl solar cell voltage is not enough to start the unit (!). Genasun has appalling efficiency.
>>> We need more info: how many Volts does your cell put out? What is the battery type and size in Watt-hours? What aircraft is this on?
>
> Genasun consumes 150mA, six times more than Victron (25 mA). My solar panel produces 550mA (via Strobl controller). Genasun robs almost third of the panel produced power.
>
The Genasum datasheet say 0.150 ma (150 ua), so much less power consumed than the Victron.

--
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

[Moshe Braner]

On 12/29/2020 1:36 PM, krasw wrote:
> On Tuesday, 29 December 2020 at 18:52:35 UTC+2, jfitch wrote:
>> I'd be amazed if you had room for a Victron in your glider. Both Victron and Genasun make generally good stuff. From the data sheets, the Victron efficiency is "98% peak" and the Genasun is "94 - 99.85% typical". These are effectively the same. What do you find appalling?
>> On Tuesday, December 29, 2020 at 8:03:58 AM UTC-8, Soartech wrote:
>>> On Tuesday, December 29, 2020 at 10:42:19 AM UTC-5, krasw wrote:
>>>> Any ideas for Strobl controller replacement? The voltage is not enough for LFP battery. Victron SmartSolar MPPT 75/10 looks good, but according to specs Strobl solar cell voltage is not enough to start the unit (!). Genasun has appalling efficiency.
>>> We need more info: how many Volts does your cell put out? What is the battery type and size in Watt-hours? What aircraft is this on?
>
> Genasun consumes 150mA, six times more than Victron (25 mA). My solar panel produces 550mA (via Strobl controller). Genasun robs almost third of the panel produced power.

I've often thought of adding small solar panels in my glider to extend
the battery life, but when I do the math it makes no sense. Most
gliders have very limited room for solar panels (unless you glue the
flexible type outside the cockpit). I am surprised you got 550 mA,
that's about 7 watts. But that's probably peak, when the panel is
perfectly aligned towards the sun, and not under a cloud, and the
average would be much lower, probably 200 mA or less. Meanwhile people
have been loading their gliders with so much electronics that they say
they need TWO 12AH batteries to last a flight. Let's take the example
of a 1-amp average load, i.e., one 12AH LFP battery (or two SLAs) would
last 12 hours. Add a 200mA-average solar charging setup and that
reduces the load on the battery to 0.8 amps, extending the battery life
to 15 hours. Useful?

[Brian[_1_]]

On Tuesday, December 29, 2020 at 8:42:19 AM UTC-7, krasw wrote:
> Any ideas for Strobl controller replacement? The voltage is not enough for LFP battery. Victron SmartSolar MPPT 75/10 looks good, but according to specs Strobl solar cell voltage is not enough to start the unit (!). Genasun has appalling efficiency.

[Brian[_1_]]

On Tuesday, December 29, 2020 at 8:42:19 AM UTC-7, krasw wrote:
> Any ideas for Strobl controller replacement? The voltage is not enough for LFP battery. Victron SmartSolar MPPT 75/10 looks good, but according to specs Strobl solar cell voltage is not enough to start the unit (!). Genasun has appalling efficiency.

I put a 10 Watt a panel on my HP16. It averaged 200-250ma charging a 12AH Lead Acid batteries. The real advantage was when I was flying contests or safaris where I left the plane tied down. I could fly about 3 days in a row without needing to charge the battery. If we had a rest day it would pretty much top off the battery. I didn’t use a charge controller, I just used a volt meter. Since I only left it tied down when I was flying almost daily I didn’t figure 200-250 was enough to hurt the battery. But if I didn’t fly for more than a day I would disconnect it.

I loved having the solar panel, most of the time I didn’t need to charge the battery when flying daily. I wish I could come up with a reasonable panel to install on my LS6.

IMO Unless you are leaving the plane outside for extended periods without flying almost daily, my opinion is you don’t need a charge controller for a 20 watt or less solar panel. An appropriately sized and heat sinked Zenor diode would prevent it from overcharging if you did inadvertently leave it connected. If it is connected only when flying then no controller is required.

[Eric Greenwell[_4_]]

Brian wrote on 12/30/2020 7:42 AM:
> On Tuesday, December 29, 2020 at 8:42:19 AM UTC-7, krasw wrote:
>> Any ideas for Strobl controller replacement? The voltage is not enough for LFP battery. Victron SmartSolar MPPT 75/10 looks good, but according to specs Strobl solar cell voltage is not enough to start the unit (!). Genasun has appalling efficiency.
>
> I put a 10 Watt a panel on my HP16. It averaged 200-250ma charging a 12AH Lead Acid batteries. The real advantage was when I was flying contests or safaris where I left the plane tied down. I could fly about 3 days in a row without needing to charge the battery. If we had a rest day it would pretty much top off the battery. I didn’t use a charge controller, I just used a volt meter. Since I only left it tied down when I was flying almost daily I didn’t figure 200-250 was enough to hurt the battery. But if I didn’t fly for more than a day I would disconnect it.
>
> I loved having the solar panel, most of the time I didn’t need to charge the battery when flying daily. I wish I could come up with a reasonable panel to install on my LS6.
>
> IMO Unless you are leaving the plane outside for extended periods without flying almost daily, my opinion is you don’t need a charge controller for a 20 watt or less solar panel. An appropriately sized and heat sinked Zenor diode would prevent it from overcharging if you did inadvertently leave it connected. If it is connected only when flying then no controller is required.
>
Brian's solution is a good one for gliders with a low enough current drain. Like Moshe, I
struggled to find a good place to put a useful amount of solar panel on my glider, given the
1.5 amp draw while flying. I eventually gave up trying, and installed a 20 AH Life battery,
which is enough capacity for two long flights. Normally, I recharge it after each flight from a
30 AH "donor" battery which is charged during the day by a 40W solar panel on the trailer,
using a DC-DC charger for electric model hobbyists. That's easy enough, and reliable.

--
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

[2G]

On Tuesday, December 29, 2020 at 7:42:19 AM UTC-8, krasw wrote:
> Any ideas for Strobl controller replacement? The voltage is not enough for LFP battery. Victron SmartSolar MPPT 75/10 looks good, but according to specs Strobl solar cell voltage is not enough to start the unit (!). Genasun has appalling efficiency.

Just take out the controller altogether. The only LFP batteries I would consider have an internal BMS (battery management system) that protects against over-charging (which won't happen airborne, anyhow). I passed on solar panels altogether for my new ASH31Mi because their output was so paltry compared to the draw of my full glass panel (2A) that it was just not worth the cost ($2,500). I put in an LFP avionics battery instead (20AHr) and supplemented that with a 12AHr battery. That works fine if I remember to turn off my master.

Tom

[2G]

On Wednesday, December 30, 2020 at 8:41:08 AM UTC-8, Eric Greenwell wrote:
> Brian wrote on 12/30/2020 7:42 AM:
> > On Tuesday, December 29, 2020 at 8:42:19 AM UTC-7, krasw wrote:
> >> Any ideas for Strobl controller replacement? The voltage is not enough for LFP battery. Victron SmartSolar MPPT 75/10 looks good, but according to specs Strobl solar cell voltage is not enough to start the unit (!). Genasun has appalling efficiency.
> >
> > I put a 10 Watt a panel on my HP16. It averaged 200-250ma charging a 12AH Lead Acid batteries. The real advantage was when I was flying contests or safaris where I left the plane tied down. I could fly about 3 days in a row without needing to charge the battery. If we had a rest day it would pretty much top off the battery. I didn’t use a charge controller, I just used a volt meter. Since I only left it tied down when I was flying almost daily I didn’t figure 200-250 was enough to hurt the battery. But if I didn’t fly for more than a day I would disconnect it.
> >
> > I loved having the solar panel, most of the time I didn’t need to charge the battery when flying daily. I wish I could come up with a reasonable panel to install on my LS6.
> >
> > IMO Unless you are leaving the plane outside for extended periods without flying almost daily, my opinion is you don’t need a charge controller for a 20 watt or less solar panel. An appropriately sized and heat sinked Zenor diode would prevent it from overcharging if you did inadvertently leave it connected. If it is connected only when flying then no controller is required.
> >
> Brian's solution is a good one for gliders with a low enough current drain. Like Moshe, I
> struggled to find a good place to put a useful amount of solar panel on my glider, given the
> 1.5 amp draw while flying. I eventually gave up trying, and installed a 20 AH Life battery,
> which is enough capacity for two long flights. Normally, I recharge it after each flight from a
> 30 AH "donor" battery which is charged during the day by a 40W solar panel on the trailer,
> using a DC-DC charger for electric model hobbyists. That's easy enough, and reliable.
> --
> 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 problem with using the glider's solar panel to recharge the battery is that there is, simply, not enough sun hours available to do the job if you fly consecutive days. To recharge a 20AHr LFP with a 200mA panel will take 100 hr - and there is only about 7 sun hours available per day. Even a partial charge would take multiple days. I do exactly what Eric does except my battery charger is AC/DC so I can choose which power source I want to use. My preference is to use AC, but that may be inconvenient at some fields. My donor batteries total 40AHr, so I can go multiple days w/o recharging them.. My only glitch to date is one solar charge controller I bought from Bioenno literally melted when left out on the ramp (they replaced it under warranty).

Tom

[krasw]

On Tuesday, 29 December 2020 at 21:27:37 UTC+2, Eric Greenwell wrote:
> krasw wrote on 12/29/2020 10:36 AM:
> > On Tuesday, 29 December 2020 at 18:52:35 UTC+2, jfitch wrote:
> >> I'd be amazed if you had room for a Victron in your glider. Both Victron and Genasun make generally good stuff. From the data sheets, the Victron efficiency is "98% peak" and the Genasun is "94 - 99.85% typical". These are effectively the same. What do you find appalling?
> >> On Tuesday, December 29, 2020 at 8:03:58 AM UTC-8, Soartech wrote:
> >>> On Tuesday, December 29, 2020 at 10:42:19 AM UTC-5, krasw wrote:
> >>>> Any ideas for Strobl controller replacement? The voltage is not enough for LFP battery. Victron SmartSolar MPPT 75/10 looks good, but according to specs Strobl solar cell voltage is not enough to start the unit (!). Genasun has appalling efficiency.
> >>> We need more info: how many Volts does your cell put out? What is the battery type and size in Watt-hours? What aircraft is this on?
> >
> > Genasun consumes 150mA, six times more than Victron (25 mA). My solar panel produces 550mA (via Strobl controller). Genasun robs almost third of the panel produced power.
> >
> The Genasum datasheet say 0.150 ma (150 ua), so much less power consumed than the Victron.
>
> --
> 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

Thanks, I should probably learn to read.

[krasw]

On Wednesday, 30 December 2020 at 01:58:04 UTC+2, Moshe Braner wrote:
> I've often thought of adding small solar panels in my glider to extend
> the battery life, but when I do the math it makes no sense. Most
> gliders have very limited room for solar panels (unless you glue the
> flexible type outside the cockpit). I am surprised you got 550 mA,
> that's about 7 watts. But that's probably peak, when the panel is
> perfectly aligned towards the sun, and not under a cloud, and the
> average would be much lower, probably 200 mA or less. Meanwhile people
> have been loading their gliders with so much electronics that they say
> they need TWO 12AH batteries to last a flight. Let's take the example
> of a 1-amp average load, i.e., one 12AH LFP battery (or two SLAs) would
> last 12 hours. Add a 200mA-average solar charging setup and that
> reduces the load on the battery to 0.8 amps, extending the battery life
> to 15 hours. Useful?

I wouldn't bother with solar panels unless my glider was factory equipped with one. My panel draws 830mA and I have 2*7 Ah of battery capacity, but OTOH I like to have one fresh battery to extend my engine in those very cold days.

[kinsell]

On 12/31/20 4:45 AM, krasw wrote:
> On Wednesday, 30 December 2020 at 01:58:04 UTC+2, Moshe Braner wrote:
>> I've often thought of adding small solar panels in my glider to extend
>> the battery life, but when I do the math it makes no sense. Most
>> gliders have very limited room for solar panels (unless you glue the
>> flexible type outside the cockpit). I am surprised you got 550 mA,
>> that's about 7 watts. But that's probably peak, when the panel is
>> perfectly aligned towards the sun, and not under a cloud, and the
>> average would be much lower, probably 200 mA or less. Meanwhile people
>> have been loading their gliders with so much electronics that they say
>> they need TWO 12AH batteries to last a flight. Let's take the example
>> of a 1-amp average load, i.e., one 12AH LFP battery (or two SLAs) would
>> last 12 hours. Add a 200mA-average solar charging setup and that
>> reduces the load on the battery to 0.8 amps, extending the battery life
>> to 15 hours. Useful?
>
> I wouldn't bother with solar panels unless my glider was factory equipped with one. My panel draws 830mA and I have 2*7 Ah of battery capacity, but OTOH I like to have one fresh battery to extend my engine in those very cold days.
>

Might want to be careful there. LFP's can be badly damaged when
charging under cold conditions.

[Moshe Braner]

On 12/31/2020 12:50 PM, kinsell wrote:
>
> Might want to be careful there.Â* LFP's can be badly damaged when
> charging under cold conditions.

Good point. "Cold" as in "below freezing" (0C, 32F) for charging, not
discharging. It seems like an arbitrary number (these batteries are not
made of water after all) but that's what they say. I'd recommend at
least several degrees above that for charging. If heading into the wave
with an LFP battery, if you have solar charging, you may want to
disconnect that (unless the charge controller does that automatically -
do the LFP-aware ones do that?). Would need a switch for that
disconnection. Otherwise it's another reason to avoid solar panels in
the glider, which can't help a lot with the battery running time anyway.

[2G]

On Thursday, December 31, 2020 at 9:50:30 AM UTC-8, kinsell wrote:
> On 12/31/20 4:45 AM, krasw wrote:
> > On Wednesday, 30 December 2020 at 01:58:04 UTC+2, Moshe Braner wrote:
> >> I've often thought of adding small solar panels in my glider to extend
> >> the battery life, but when I do the math it makes no sense. Most
> >> gliders have very limited room for solar panels (unless you glue the
> >> flexible type outside the cockpit). I am surprised you got 550 mA,
> >> that's about 7 watts. But that's probably peak, when the panel is
> >> perfectly aligned towards the sun, and not under a cloud, and the
> >> average would be much lower, probably 200 mA or less. Meanwhile people
> >> have been loading their gliders with so much electronics that they say
> >> they need TWO 12AH batteries to last a flight. Let's take the example
> >> of a 1-amp average load, i.e., one 12AH LFP battery (or two SLAs) would
> >> last 12 hours. Add a 200mA-average solar charging setup and that
> >> reduces the load on the battery to 0.8 amps, extending the battery life
> >> to 15 hours. Useful?
> >
> > I wouldn't bother with solar panels unless my glider was factory equipped with one. My panel draws 830mA and I have 2*7 Ah of battery capacity, but OTOH I like to have one fresh battery to extend my engine in those very cold days.
> >
> Might want to be careful there. LFP's can be badly damaged when
> charging under cold conditions.

That is independent of whether or not a solar charge controller is used. You can always add a switch to disconnect it, or omit the solar panels altogether (which is what I did).

Tom

[2G]

On Thursday, December 31, 2020 at 11:11:12 AM UTC-8, Moshe Braner wrote:
> On 12/31/2020 12:50 PM, kinsell wrote:
> >
> > Might want to be careful there. LFP's can be badly damaged when
> > charging under cold conditions.
> Good point. "Cold" as in "below freezing" (0C, 32F) for charging, not
> discharging. It seems like an arbitrary number (these batteries are not
> made of water after all) but that's what they say. I'd recommend at
> least several degrees above that for charging. If heading into the wave
> with an LFP battery, if you have solar charging, you may want to
> disconnect that (unless the charge controller does that automatically -
> do the LFP-aware ones do that?). Would need a switch for that
> disconnection. Otherwise it's another reason to avoid solar panels in
> the glider, which can't help a lot with the battery running time anyway.

If you're airborne it doesn't matter because the output of the panel goes totally towards powering the avionics and no charging is happening.

Tom

[Eric Greenwell[_4_]]

Moshe Braner wrote on 12/31/2020 11:12 AM:
> On 12/31/2020 12:50 PM, kinsell wrote:
>>
>> Might want to be careful there.* LFP's can be badly damaged when charging under cold conditions.
>
> Good point.* "Cold" as in "below freezing" (0C, 32F) for charging, not discharging.* It seems
> like an arbitrary number (these batteries are not made of water after all) but that's what they
> say.* I'd recommend at least several degrees above that for charging.* If heading into the wave
> with an LFP battery, if you have solar charging, you may want to disconnect that (unless the
> charge controller does that automatically - do the LFP-aware ones do that?).* Would need a
> switch for that disconnection.* Otherwise it's another reason to avoid solar panels in the
> glider, which can't help a lot with the battery running time anyway.

Do some LiFe batteries with a BMS stop charging at a low temperature? If so, maybe that's one
to put in the glider.

--
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

[jfitch]

Using the BMS to control charging is not considered good engineering practice. The BMS may or may not be designed to operate that way, but once it disconnects the power bus driven by the solar will be at uncontrolled and possibly damaging voltage. Also, different designs of BMS reset (and reconnect) in different ways, and maybe not how you expected.

On Thursday, December 31, 2020 at 3:25:05 PM UTC-8, Eric Greenwell wrote:
> Moshe Braner wrote on 12/31/2020 11:12 AM:
> > On 12/31/2020 12:50 PM, kinsell wrote:
> >>
> >> Might want to be careful there. LFP's can be badly damaged when charging under cold conditions.
> >
> > Good point. "Cold" as in "below freezing" (0C, 32F) for charging, not discharging. It seems
> > like an arbitrary number (these batteries are not made of water after all) but that's what they
> > say. I'd recommend at least several degrees above that for charging. If heading into the wave
> > with an LFP battery, if you have solar charging, you may want to disconnect that (unless the
> > charge controller does that automatically - do the LFP-aware ones do that?). Would need a
> > switch for that disconnection. Otherwise it's another reason to avoid solar panels in the
> > glider, which can't help a lot with the battery running time anyway.
> Do some LiFe batteries with a BMS stop charging at a low temperature? If so, maybe that's one
> to put in the glider.
> --
> 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]

On 12/31/20 12:12 PM, Moshe Braner wrote:
> On 12/31/2020 12:50 PM, kinsell wrote:
>>
>> Might want to be careful there.Â* LFP's can be badly damaged when
>> charging under cold conditions.
>
> Good point.Â* "Cold" as in "below freezing" (0C, 32F) for charging, not
> discharging.Â* It seems like an arbitrary number (these batteries are not
> made of water after all) but that's what they say.Â* I'd recommend at
> least several degrees above that for charging.Â* If heading into the wave
> with an LFP battery, if you have solar charging, you may want to
> disconnect that (unless the charge controller does that automatically -
> do the LFP-aware ones do that?).Â* Would need a switch for that
> disconnection.Â* Otherwise it's another reason to avoid solar panels in
> the glider, which can't help a lot with the battery running time anyway.

I have a toggle switch to switch between my LiFePO4 in the baggage area
and my Pb battery in the tail. I have a separate switch to switch the
main battery and the aux battery. I flew around at 16 deg F for almost
4 hours and had no trouble with the batteries or the solar panels (5 of
them). Just because the OAT is below freezing does not mean the the
batteries are getting that cold in the cockpit. The tail battery,
however, could get pretty cold, but it's a Pb battery.

--
Dan
5J

[2G]

On Thursday, December 31, 2020 at 4:08:21 PM UTC-8, jfitch wrote:
> Using the BMS to control charging is not considered good engineering practice. The BMS may or may not be designed to operate that way, but once it disconnects the power bus driven by the solar will be at uncontrolled and possibly damaging voltage. Also, different designs of BMS reset (and reconnect) in different ways, and maybe not how you expected.
> On Thursday, December 31, 2020 at 3:25:05 PM UTC-8, Eric Greenwell wrote:
> > Moshe Braner wrote on 12/31/2020 11:12 AM:
> > > On 12/31/2020 12:50 PM, kinsell wrote:
> > >>
> > >> Might want to be careful there. LFP's can be badly damaged when charging under cold conditions.
> > >
> > > Good point. "Cold" as in "below freezing" (0C, 32F) for charging, not discharging. It seems
> > > like an arbitrary number (these batteries are not made of water after all) but that's what they
> > > say. I'd recommend at least several degrees above that for charging. If heading into the wave
> > > with an LFP battery, if you have solar charging, you may want to disconnect that (unless the
> > > charge controller does that automatically - do the LFP-aware ones do that?). Would need a
> > > switch for that disconnection. Otherwise it's another reason to avoid solar panels in the
> > > glider, which can't help a lot with the battery running time anyway.
> > Do some LiFe batteries with a BMS stop charging at a low temperature? If so, maybe that's one
> > to put in the glider.
> > --
> > 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 BMS is being used for exactly what it is designed for: preventing over-voltage charging. Any question about recovering from an over-charge condition should be directed at the battery manufacturer, not speculated on. Additionally, the solar panel isn't charging the battery at all in flight, so this would only be an issue on the ground. My position is don't bother with the panels, they just don't contribute that much.

Tom

[jfitch]

Most of the industry doesn't agree with you, but I expect you're used to that situation. The BMS is usually regarded as a safety device, the controller of last resort, to prevent fault conditions. What you propose is kind of like using the over current circuit breaker as the limit stop on your motor jack. Run 'er 'till she trips. Yeah it works, but not the best way. There is little downside in having a proper charge controller, and much potential downside in leaving it out.

On Thursday, December 31, 2020 at 6:19:20 PM UTC-8, 2G wrote:
> On Thursday, December 31, 2020 at 4:08:21 PM UTC-8, jfitch wrote:
> > Using the BMS to control charging is not considered good engineering practice. The BMS may or may not be designed to operate that way, but once it disconnects the power bus driven by the solar will be at uncontrolled and possibly damaging voltage. Also, different designs of BMS reset (and reconnect) in different ways, and maybe not how you expected.
> > On Thursday, December 31, 2020 at 3:25:05 PM UTC-8, Eric Greenwell wrote:
> > > Moshe Braner wrote on 12/31/2020 11:12 AM:
> > > > On 12/31/2020 12:50 PM, kinsell wrote:
> > > >>
> > > >> Might want to be careful there. LFP's can be badly damaged when charging under cold conditions.
> > > >
> > > > Good point. "Cold" as in "below freezing" (0C, 32F) for charging, not discharging. It seems
> > > > like an arbitrary number (these batteries are not made of water after all) but that's what they
> > > > say. I'd recommend at least several degrees above that for charging.. If heading into the wave
> > > > with an LFP battery, if you have solar charging, you may want to disconnect that (unless the
> > > > charge controller does that automatically - do the LFP-aware ones do that?). Would need a
> > > > switch for that disconnection. Otherwise it's another reason to avoid solar panels in the
> > > > glider, which can't help a lot with the battery running time anyway..
> > > Do some LiFe batteries with a BMS stop charging at a low temperature? If so, maybe that's one
> > > to put in the glider.
> > > --
> > > 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 BMS is being used for exactly what it is designed for: preventing over-voltage charging. Any question about recovering from an over-charge condition should be directed at the battery manufacturer, not speculated on. Additionally, the solar panel isn't charging the battery at all in flight, so this would only be an issue on the ground. My position is don't bother with the panels, they just don't contribute that much.
>
> Tom

[krasw]

Re: cold weather, I have charged LFP batteries for years in cold hangar (often below zero at night) without any problems. Solar panels do not charge batteries, unless your glider is on the ground with all devices off.

I have 100k glider with 2k solar panels, I still have 100 bucks left for solar panel controller.

[2G]

On Friday, January 1, 2021 at 8:47:15 AM UTC-8, jfitch wrote:
> Most of the industry doesn't agree with you, but I expect you're used to that situation. The BMS is usually regarded as a safety device, the controller of last resort, to prevent fault conditions. What you propose is kind of like using the over current circuit breaker as the limit stop on your motor jack. Run 'er 'till she trips. Yeah it works, but not the best way. There is little downside in having a proper charge controller, and much potential downside in leaving it out.
> On Thursday, December 31, 2020 at 6:19:20 PM UTC-8, 2G wrote:
> > On Thursday, December 31, 2020 at 4:08:21 PM UTC-8, jfitch wrote:
> > > Using the BMS to control charging is not considered good engineering practice. The BMS may or may not be designed to operate that way, but once it disconnects the power bus driven by the solar will be at uncontrolled and possibly damaging voltage. Also, different designs of BMS reset (and reconnect) in different ways, and maybe not how you expected.
> > > On Thursday, December 31, 2020 at 3:25:05 PM UTC-8, Eric Greenwell wrote:
> > > > Moshe Braner wrote on 12/31/2020 11:12 AM:
> > > > > On 12/31/2020 12:50 PM, kinsell wrote:
> > > > >>
> > > > >> Might want to be careful there. LFP's can be badly damaged when charging under cold conditions.
> > > > >
> > > > > Good point. "Cold" as in "below freezing" (0C, 32F) for charging, not discharging. It seems
> > > > > like an arbitrary number (these batteries are not made of water after all) but that's what they
> > > > > say. I'd recommend at least several degrees above that for charging. If heading into the wave
> > > > > with an LFP battery, if you have solar charging, you may want to disconnect that (unless the
> > > > > charge controller does that automatically - do the LFP-aware ones do that?). Would need a
> > > > > switch for that disconnection. Otherwise it's another reason to avoid solar panels in the
> > > > > glider, which can't help a lot with the battery running time anyway.
> > > > Do some LiFe batteries with a BMS stop charging at a low temperature? If so, maybe that's one
> > > > to put in the glider.
> > > > --
> > > > 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 BMS is being used for exactly what it is designed for: preventing over-voltage charging. Any question about recovering from an over-charge condition should be directed at the battery manufacturer, not speculated on. Additionally, the solar panel isn't charging the battery at all in flight, so this would only be an issue on the ground. My position is don't bother with the panels, they just don't contribute that much.
> >
> > Tom

The recommendation WAS intended as the course of last resort if an appropriate solar charge controller was unavailable.

Tom

[Rhubarb[_2_]]

https://airbatt.de/navi.php?a=9114&lang=eng

[2G]

On Monday, January 4, 2021 at 7:41:18 AM UTC-8, Rhubarb wrote:
> https://airbatt.de/navi.php?a=9114&lang=eng

Unfortunately they don't ship to countries outside of Europe.

Tom

[Dan Marotta]

On 1/4/21 2:22 PM, 2G wrote:
> On Monday, January 4, 2021 at 7:41:18 AM UTC-8, Rhubarb wrote:
>> https://airbatt.de/navi.php?a=9114&lang=eng
>
> Unfortunately they don't ship to countries outside of Europe.
>
> Tom
>
I have one of these:
https://smile.amazon.com/gp/product/B008KWPGS6/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

--
Dan
5J

[2G]

On Monday, January 4, 2021 at 3:32:11 PM UTC-8, Dan Marotta wrote:
> On 1/4/21 2:22 PM, 2G wrote:
> > On Monday, January 4, 2021 at 7:41:18 AM UTC-8, Rhubarb wrote:
> >> https://airbatt.de/navi.php?a=9114&lang=eng
> >
> > Unfortunately they don't ship to countries outside of Europe.
> >
> > Tom
> >
> I have one of these:
> https://smile.amazon.com/gp/product/B008KWPGS6/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
>
> --
> Dan
> 5J
Besides been quite large and unavailable, it is not for use with LFP batteries.

Tom

[krasw]

On Monday, 4 January 2021 at 23:22:14 UTC+2, 2G wrote:
> On Monday, January 4, 2021 at 7:41:18 AM UTC-8, Rhubarb wrote:
> > https://airbatt.de/navi.php?a=9114&lang=eng
>
> Unfortunately they don't ship to countries outside of Europe.
>
> Tom

Well that's not a problem for me, but I don't buy anything from AIRBATT. They sold me a crap chinese LFP battery rebadged with AIRBATT-sticker, which then died after a year of use (BMS failure, unrepairable). First they tried to charge me for checking the battery, after sending it back at my expense. Then they told my that their battery warranty policy follows basically the same EU regulation as warranty for a banana bought from grocery store, and effectively told me to **** off. At a same time local car parts store gives 5 years no-hassle warranty to their cheapest made-in-poland car battery..

[Dan Marotta]

On 1/4/21 6:35 PM, 2G wrote:
> On Monday, January 4, 2021 at 3:32:11 PM UTC-8, Dan Marotta wrote:
>> On 1/4/21 2:22 PM, 2G wrote:
>>> On Monday, January 4, 2021 at 7:41:18 AM UTC-8, Rhubarb wrote:
>>>> https://airbatt.de/navi.php?a=9114&lang=eng
>>>
>>> Unfortunately they don't ship to countries outside of Europe.
>>>
>>> Tom
>>>
>> I have one of these:
>> https://smile.amazon.com/gp/product/B008KWPGS6/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
>>
>> --
>> Dan
>> 5J
> Besides been quite large and unavailable, it is not for use with LFP batteries.
>
> Tom
>

Oops, I thought the thread was about charge controllers, not about the
batteries they're charging.

There ARE MPPT chargers suitable for LiFePO4, however. They do cost
quite a bit more but they deliver a higher percentage of the energy to
the batteries.

--
Dan
5J

[Eric Greenwell[_4_]]

Dan Marotta wrote on 1/5/2021 8:19 AM:
> On 1/4/21 6:35 PM, 2G wrote:
>> On Monday, January 4, 2021 at 3:32:11 PM UTC-8, Dan Marotta wrote:
>>> On 1/4/21 2:22 PM, 2G wrote:
>>>> On Monday, January 4, 2021 at 7:41:18 AM UTC-8, Rhubarb wrote:
>>>>> https://airbatt.de/navi.php?a=9114&lang=eng
>>>>
>>>> Unfortunately they don't ship to countries outside of Europe.
>>>>
>>>> Tom
>>>>
>>> I have one of these:
>>> https://smile.amazon.com/gp/product/B008KWPGS6/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
>>>
>>> --
>>> Dan
>>> 5J
>> Besides been quite large and unavailable, it is not for use with LFP batteries.
>>
>> Tom
>>
>
> Oops, I thought the thread was about charge controllers, not about the batteries they're charging.
>
> There ARE MPPT chargers suitable for LiFePO4, however.* They do cost quite a bit more but they
> deliver a higher percentage of the energy to the batteries.
>
For glider use, they may not be worth the extra size, weight, and cost. It depends on the solar
panels, and the ones for gliders are usually chosen to optimize charging of 12 volt batteries
with PWM charge controllers, and using an MPPT controller on those panels will gain little
extra charging.

If the panels could be rewired in series instead of in parallel, the MPPT controller may
improve the charging rate. It's possible the constant changing of panel orientation in flight
may render the MPPT controller ineffective; on the ground it's probably similar to an RV, where
the range is often given at 10%-30% short term improvement, and perhaps as much as 15% average
over a few months use.

I've been researching this issue for my motorhome; currently (little pun there), I'm leaning to
doubling the size of the system as simply and cheaply as possible by duplicating the system it
already has, and paralleling the output from the two PWM controllers to the battery. If actual
usage shows another 15% charging would be worthwhile, I'll replace the PWM controllers with
MPPT units at about $200-$300 additional parts cost. I suspect additional batteries will be a
better way to spend $200, however.

--
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]

On 1/5/21 11:41 AM, Eric Greenwell wrote:
> the ones for gliders are usually chosen to optimize charging of 12 volt
> batteries with PWM charge controllers, and using an MPPT controller on
> those panels will gain little extra charging.

I'd like to see a proof of that...

--
Dan
5J

[Eric Greenwell[_4_]]

Dan Marotta wrote on 1/5/2021 10:48 AM:
> On 1/5/21 11:41 AM, Eric Greenwell wrote:
>> the ones for gliders are usually chosen to optimize charging of 12 volt batteries with PWM
>> charge controllers, and using an MPPT controller on those panels will gain little extra
>> charging.
>
> I'd like to see a proof of that...
>
Which statement: glider panels chosen to optimize PWM, or MPPT controller won't help with that
type panel (ie, low voltage output)? In general, though, the big difference is PWM is more
efficient with low voltage panels (like 18 volts), and MPPT is more efficient with higher
voltages (at least 24 volts, 30 is better).

Do you have the specs for your Stemme panels?

--
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

[2G]

On Tuesday, January 5, 2021 at 4:58:48 PM UTC-8, Eric Greenwell wrote:
> Dan Marotta wrote on 1/5/2021 10:48 AM:
> > On 1/5/21 11:41 AM, Eric Greenwell wrote:
> >> the ones for gliders are usually chosen to optimize charging of 12 volt batteries with PWM
> >> charge controllers, and using an MPPT controller on those panels will gain little extra
> >> charging.
> >
> > I'd like to see a proof of that...
> >
> Which statement: glider panels chosen to optimize PWM, or MPPT controller won't help with that
> type panel (ie, low voltage output)? In general, though, the big difference is PWM is more
> efficient with low voltage panels (like 18 volts), and MPPT is more efficient with higher
> voltages (at least 24 volts, 30 is better).
>
> Do you have the specs for your Stemme panels?
> --
> 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

That doesn't make sense: an MPPT controller IS a PWM power converter, it just optimizes the operating point.
https://www.researchgate.net/profile/Rajeev_Valunjkar/publication/317723124_Designing_and_implementation_of_maximum_ power_point_trackingMPPT_solar_charge_controller/links/5b0540a7a6fdcc91ed8a9f74/Designing-and-implementation-of-maximum-power-point-trackingMPPT-solar-charge-controller.pdf

The advantages of a higher voltage panel are:
1. Lower percentage losses in the MOSFET switch (not much of a factor).
2. Wider operating point to deal with less sunlight.

Tom

[Eric Greenwell[_4_]]

2G wrote on 1/5/2021 6:52 PM:
> On Tuesday, January 5, 2021 at 4:58:48 PM UTC-8, Eric Greenwell wrote:
>> Dan Marotta wrote on 1/5/2021 10:48 AM:
>>> On 1/5/21 11:41 AM, Eric Greenwell wrote:
>>>> the ones for gliders are usually chosen to optimize charging of 12 volt batteries with PWM
>>>> charge controllers, and using an MPPT controller on those panels will gain little extra
>>>> charging.
>>>
>>> I'd like to see a proof of that...
>>>
>> Which statement: glider panels chosen to optimize PWM, or MPPT controller won't help with that
>> type panel (ie, low voltage output)? In general, though, the big difference is PWM is more
>> efficient with low voltage panels (like 18 volts), and MPPT is more efficient with higher
>> voltages (at least 24 volts, 30 is better).
>>
>> Do you have the specs for your Stemme panels?
>> --
>> 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
>
> That doesn't make sense: an MPPT controller IS a PWM power converter, it just optimizes the operating point.
> https://www.researchgate.net/profile/Rajeev_Valunjkar/publication/317723124_Designing_and_implementation_of_maximum_ power_point_trackingMPPT_solar_charge_controller/links/5b0540a7a6fdcc91ed8a9f74/Designing-and-implementation-of-maximum-power-point-trackingMPPT-solar-charge-controller.pdf
>
> The advantages of a higher voltage panel are:
> 1. Lower percentage losses in the MOSFET switch (not much of a factor).
> 2. Wider operating point to deal with less sunlight.
>
> Tom


An MPPT charge controller includes a DC-DC converter (called a "buck" converter in the paper
you reference) to convert power at the MPP voltage to the battery voltage needed for charging.
A PWM charge controller, in the context of solar power systems charging batteries does not have
the DC-DC converter. It just switches the panel on and off to the battery - no power conversion.

Here's an example: My motorhome has two 100W panels in parallel, producing about 11 amps
charging in good conditions. If I were to put the panels in series while using the PWM
controller, the system would produce about 5 amps. If instead, I used an MPPT controller on
that same two panels in series, it could produce about 14 amps of charging.

--
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

[2G]

On Tuesday, January 5, 2021 at 8:57:17 PM UTC-8, Eric Greenwell wrote:
> 2G wrote on 1/5/2021 6:52 PM:
> > On Tuesday, January 5, 2021 at 4:58:48 PM UTC-8, Eric Greenwell wrote:
> >> Dan Marotta wrote on 1/5/2021 10:48 AM:
> >>> On 1/5/21 11:41 AM, Eric Greenwell wrote:
> >>>> the ones for gliders are usually chosen to optimize charging of 12 volt batteries with PWM
> >>>> charge controllers, and using an MPPT controller on those panels will gain little extra
> >>>> charging.
> >>>
> >>> I'd like to see a proof of that...
> >>>
> >> Which statement: glider panels chosen to optimize PWM, or MPPT controller won't help with that
> >> type panel (ie, low voltage output)? In general, though, the big difference is PWM is more
> >> efficient with low voltage panels (like 18 volts), and MPPT is more efficient with higher
> >> voltages (at least 24 volts, 30 is better).
> >>
> >> Do you have the specs for your Stemme panels?
> >> --
> >> 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
> >
> > That doesn't make sense: an MPPT controller IS a PWM power converter, it just optimizes the operating point.
> > https://www.researchgate.net/profile/Rajeev_Valunjkar/publication/317723124_Designing_and_implementation_of_maximum_ power_point_trackingMPPT_solar_charge_controller/links/5b0540a7a6fdcc91ed8a9f74/Designing-and-implementation-of-maximum-power-point-trackingMPPT-solar-charge-controller.pdf
> >
> > The advantages of a higher voltage panel are:
> > 1. Lower percentage losses in the MOSFET switch (not much of a factor).
> > 2. Wider operating point to deal with less sunlight.
> >
> > Tom
> An MPPT charge controller includes a DC-DC converter (called a "buck" converter in the paper
> you reference) to convert power at the MPP voltage to the battery voltage needed for charging.
> A PWM charge controller, in the context of solar power systems charging batteries does not have
> the DC-DC converter. It just switches the panel on and off to the battery - no power conversion.
>
> Here's an example: My motorhome has two 100W panels in parallel, producing about 11 amps
> charging in good conditions. If I were to put the panels in series while using the PWM
> controller, the system would produce about 5 amps. If instead, I used an MPPT controller on
> that same two panels in series, it could produce about 14 amps of charging.
> --
> 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

A dc-dc converter IS pulse-width modulated (PWM). A series switching MOSFET is turned on and off (pulse-width modulated) to regulate current in an inductor. Here is an excerpt of the article I referenced:

" Then depending upon power level it gives PWM input to buck converter which
decides whether the solar panel is to be connected to battery or not for charging."

Tom

[Eric Greenwell[_4_]]

2G wrote on 1/6/2021 3:24 PM:
> On Tuesday, January 5, 2021 at 8:57:17 PM UTC-8, Eric Greenwell wrote:
>> 2G wrote on 1/5/2021 6:52 PM:
>>> On Tuesday, January 5, 2021 at 4:58:48 PM UTC-8, Eric Greenwell wrote:
>>>> Dan Marotta wrote on 1/5/2021 10:48 AM:
>>>>> On 1/5/21 11:41 AM, Eric Greenwell wrote:
>>>>>> the ones for gliders are usually chosen to optimize charging of 12 volt batteries with PWM
>>>>>> charge controllers, and using an MPPT controller on those panels will gain little extra
>>>>>> charging.
>>>>>
>>>>> I'd like to see a proof of that...
>>>>>
>>>> Which statement: glider panels chosen to optimize PWM, or MPPT controller won't help with that
>>>> type panel (ie, low voltage output)? In general, though, the big difference is PWM is more
>>>> efficient with low voltage panels (like 18 volts), and MPPT is more efficient with higher
>>>> voltages (at least 24 volts, 30 is better).
>>>>
>>>> Do you have the specs for your Stemme panels?
>>>> --
>>>> 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
>>>
>>> That doesn't make sense: an MPPT controller IS a PWM power converter, it just optimizes the operating point.
>>> https://www.researchgate.net/profile/Rajeev_Valunjkar/publication/317723124_Designing_and_implementation_of_maximum_ power_point_trackingMPPT_solar_charge_controller/links/5b0540a7a6fdcc91ed8a9f74/Designing-and-implementation-of-maximum-power-point-trackingMPPT-solar-charge-controller.pdf
>>>
>>> The advantages of a higher voltage panel are:
>>> 1. Lower percentage losses in the MOSFET switch (not much of a factor).
>>> 2. Wider operating point to deal with less sunlight.
>>>
>>> Tom
>> An MPPT charge controller includes a DC-DC converter (called a "buck" converter in the paper
>> you reference) to convert power at the MPP voltage to the battery voltage needed for charging.
>> A PWM charge controller, in the context of solar power systems charging batteries does not have
>> the DC-DC converter. It just switches the panel on and off to the battery - no power conversion.
>>
>> Here's an example: My motorhome has two 100W panels in parallel, producing about 11 amps
>> charging in good conditions. If I were to put the panels in series while using the PWM
>> controller, the system would produce about 5 amps. If instead, I used an MPPT controller on
>> that same two panels in series, it could produce about 14 amps of charging.
>> --
>> 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
>
> A dc-dc converter IS pulse-width modulated (PWM). A series switching MOSFET is turned on and off (pulse-width modulated) to regulate current in an inductor. Here is an excerpt of the article I referenced:
>
> " Then depending upon power level it gives PWM input to buck converter which
> decides whether the solar panel is to be connected to battery or not for charging."
>
> Tom
In the solar battery charging context we are discussing, the label "PWM" refers to controllers
that directly connect the solar panel to the battery with a switch to charge it. When the
switch closes, the panel voltage drops to the battery voltage, so the charging current is
limited to what the panel can put out at the battery's voltage.

The label "MPPT" refers to controllers that have a logic controlled DC to DC converter in them
that allows the controller to adjust the the DC-DC converter to maintain the panel voltage
where the panel is putting out maximum power while DC-DC converter output is at the battery
voltage, and the current is higher than the panel is putting out.

So, in this context, PWM and MPPT refer to significantly different types of controllers, and
it's irrelevant if the DC-DC converter uses pulse width modulation to control the DC-DC
converter. Using the labels as I've described is common industry practice, even in the paper
you referenced.


--
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

[2G]

On Wednesday, January 6, 2021 at 3:51:57 PM UTC-8, Eric Greenwell wrote:
> 2G wrote on 1/6/2021 3:24 PM:
> > On Tuesday, January 5, 2021 at 8:57:17 PM UTC-8, Eric Greenwell wrote:
> >> 2G wrote on 1/5/2021 6:52 PM:
> >>> On Tuesday, January 5, 2021 at 4:58:48 PM UTC-8, Eric Greenwell wrote:
> >>>> Dan Marotta wrote on 1/5/2021 10:48 AM:
> >>>>> On 1/5/21 11:41 AM, Eric Greenwell wrote:
> >>>>>> the ones for gliders are usually chosen to optimize charging of 12 volt batteries with PWM
> >>>>>> charge controllers, and using an MPPT controller on those panels will gain little extra
> >>>>>> charging.
> >>>>>
> >>>>> I'd like to see a proof of that...
> >>>>>
> >>>> Which statement: glider panels chosen to optimize PWM, or MPPT controller won't help with that
> >>>> type panel (ie, low voltage output)? In general, though, the big difference is PWM is more
> >>>> efficient with low voltage panels (like 18 volts), and MPPT is more efficient with higher
> >>>> voltages (at least 24 volts, 30 is better).
> >>>>
> >>>> Do you have the specs for your Stemme panels?
> >>>> --
> >>>> 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
> >>>
> >>> That doesn't make sense: an MPPT controller IS a PWM power converter, it just optimizes the operating point.
> >>> https://www.researchgate.net/profile/Rajeev_Valunjkar/publication/317723124_Designing_and_implementation_of_maximum_ power_point_trackingMPPT_solar_charge_controller/links/5b0540a7a6fdcc91ed8a9f74/Designing-and-implementation-of-maximum-power-point-trackingMPPT-solar-charge-controller.pdf
> >>>
> >>> The advantages of a higher voltage panel are:
> >>> 1. Lower percentage losses in the MOSFET switch (not much of a factor).
> >>> 2. Wider operating point to deal with less sunlight.
> >>>
> >>> Tom
> >> An MPPT charge controller includes a DC-DC converter (called a "buck" converter in the paper
> >> you reference) to convert power at the MPP voltage to the battery voltage needed for charging.
> >> A PWM charge controller, in the context of solar power systems charging batteries does not have
> >> the DC-DC converter. It just switches the panel on and off to the battery - no power conversion.
> >>
> >> Here's an example: My motorhome has two 100W panels in parallel, producing about 11 amps
> >> charging in good conditions. If I were to put the panels in series while using the PWM
> >> controller, the system would produce about 5 amps. If instead, I used an MPPT controller on
> >> that same two panels in series, it could produce about 14 amps of charging.
> >> --
> >> 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
> >
> > A dc-dc converter IS pulse-width modulated (PWM). A series switching MOSFET is turned on and off (pulse-width modulated) to regulate current in an inductor. Here is an excerpt of the article I referenced:
> >
> > " Then depending upon power level it gives PWM input to buck converter which
> > decides whether the solar panel is to be connected to battery or not for charging."
> >
> > Tom
> In the solar battery charging context we are discussing, the label "PWM" refers to controllers
> that directly connect the solar panel to the battery with a switch to charge it. When the
> switch closes, the panel voltage drops to the battery voltage, so the charging current is
> limited to what the panel can put out at the battery's voltage.
>
> The label "MPPT" refers to controllers that have a logic controlled DC to DC converter in them
> that allows the controller to adjust the the DC-DC converter to maintain the panel voltage
> where the panel is putting out maximum power while DC-DC converter output is at the battery
> voltage, and the current is higher than the panel is putting out.
>
> So, in this context, PWM and MPPT refer to significantly different types of controllers, and
> it's irrelevant if the DC-DC converter uses pulse width modulation to control the DC-DC
> converter. Using the labels as I've described is common industry practice, even in the paper
> you referenced.
> --
> 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

Ok, but the terminology is a bit confusing as they are both PWM controllers.. This Genasun MPPT controller is widely available and has been recommended on RAS before as a STROBL replacement:

https://www.amazon.com/Genasun-GV-5-Li-14-2V-Controller-Lithium-Batteries/dp/B01N9BP7VL

Tom