Some LiFePO4 Battery Testing Results Manual and Automated

[John DeRosa OHM Ω http://aviation.derosaweb.net]

Every year I test my two LiFePO4 batteries to gauge how long they will last during a flight. I decided to open the field a bit and also tested some soaring friend's batteries.

You can read about my simple cheap manual process (later automated - see below) here > http://aviation.derosaweb.net/#batterytest which was also detailed in Soaring (Feb 2012). Yeah, I know there are automated testers on the market but I want to create something cheap that everyone can make.

My battery go/no-go is how long it will take for the battery to drop to 12.0Vdc with a continuous 12Ω (~1A) resistive load. Here is what I found;

2013 Bioenno Model BLF-1209T- 6.5H
2015 Stark Model SP-12V9-EF - 5.5h
2015 Bioenno Model HN12V9AHF- 7.0H
2017 Bioenno model BLF-1209WS - 9.0H

Full details of my results can be found here > http://aviation.derosaweb.net/batterytest/Battery_Testing_Results_04.08.19.pdf

Anyone else tested their batteries in this same way? What are your results?

Automation - Manually gathering data every 10 minutes for 6-9 hours on four different batteries is tedious at best. I watched a lot of movies. So I decided to automate the process with an cheap $10 Arduino Duo. The Arduino software takes a reading at different points of time based on the current voltage. Every one minute at the beginning and end of the test, and every 10 minutes in the middle.

It still takes 6-9 hours to run the test but recording the voltages is fully automated so running the test is a start-then-walk-away-and-come-back-later-for-the-findings kind of deal. Luckily with the LiFePO4 batteries when they get below ~11.0Vdc the BMS basically shuts the battery off. The program detects any voltage drop below 8Vdc and terminates itself.

If anyone is interested in duplicating my Arduino test rig, drop me a line and I will share the details. My Arduino code can be found at http://aviation.derosaweb.net/batterytest/arduino.

John OHM Ω

[[email protected]]

On Wednesday, April 17, 2019 at 6:58:40 PM UTC-7, John DeRosa OHM Ω http://aviation.derosaweb.net wrote:
> Every year I test my two LiFePO4 batteries to gauge how long they will last during a flight. I decided to open the field a bit and also tested some soaring friend's batteries.
>
> You can read about my simple cheap manual process (later automated - see below) here > http://aviation.derosaweb.net/#batterytest which was also detailed in Soaring (Feb 2012). Yeah, I know there are automated testers on the market but I want to create something cheap that everyone can make.
>
> My battery go/no-go is how long it will take for the battery to drop to 12.0Vdc with a continuous 12Ω (~1A) resistive load. Here is what I found;
>
> 2013 Bioenno Model BLF-1209T- 6.5H
> 2015 Stark Model SP-12V9-EF - 5.5h
> 2015 Bioenno Model HN12V9AHF- 7.0H
> 2017 Bioenno model BLF-1209WS - 9.0H
>
> Full details of my results can be found here > http://aviation.derosaweb.net/batterytest/Battery_Testing_Results_04.08.19.pdf
>
> Anyone else tested their batteries in this same way? What are your results?
>
> Automation - Manually gathering data every 10 minutes for 6-9 hours on four different batteries is tedious at best. I watched a lot of movies. So I decided to automate the process with an cheap $10 Arduino Duo. The Arduino software takes a reading at different points of time based on the current voltage. Every one minute at the beginning and end of the test, and every 10 minutes in the middle.
>
> It still takes 6-9 hours to run the test but recording the voltages is fully automated so running the test is a start-then-walk-away-and-come-back-later-for-the-findings kind of deal. Luckily with the LiFePO4 batteries when they get below ~11.0Vdc the BMS basically shuts the battery off. The program detects any voltage drop below 8Vdc and terminates itself.
>
> If anyone is interested in duplicating my Arduino test rig, drop me a line and I will share the details. My Arduino code can be found at http://aviation.derosaweb.net/batterytest/arduino.
>
> John OHM Ω

Well done John - very impressive, and a fun project.

I'm some combination of too busy and too lazy, so I spent $179 on one of these. I still watch movies, but maybe not under duress. ;-)

https://www.dxengineering.com/parts/wmt-58250-1014?seid=dxese1&cm_mmc=pla-google-_-shopping-_-dxese1-_-west-mountain-radio&gclid=CjwKCAjwndvlBRANEiwABrR32CXOrIAz3oo94ATkfYT3 ymfE_3qPwmECllvf45DKtX6FW6giVCuLbRoCOCcQAvD_BwE

Andy

[krasw]

My battery analyzer is based on this cheap chinese coulometer:

https://www.ebay.com/itm/DC8-80V-50A-Battery-Coulometer-TK15-Professional-Precision-LiFePO-Battery-Tester-/252470874308

I use small car light bulb (10-20W) as a load.

I connect the thing between charger and batter or load and battery. That way I can measure capacity both ways. It is also super easy to discharge battery to optimum state for winter storage.

I like it so much I seriously thought about putting it my glider panel. If it only would support 2 or 3 batteries.

[Maxx Ruff[_2_]]

Checkout (Google) "ZB2L3" or "Battery Capacity Meter Discharge Tester
Analyzer". (Less than $10, 15 volts max, doesn't provide a log, just
shows capacity)

I used an old micro-USB phone charger to power the tester. (Low-power
is OK as it is not doing any charging).

For the load I used a couple of 7 Watt car taillight bulbs in parallel.
(The
resistors supplied with the tester are not suitable as they get too hot at

12 volts)
I mounted everything in an old metal toolbox.

Easy to use, cuts out at the voltage you choose, shows capacity in amp-
hours.

I've been using 6 of these for years, haven't had any problems.

I get much more repeatable results if I only test batteries that have
been left on charge for a few days after the 'full' light illuminates.
I suspect that lithium chargers may indicate 'full' a bit early while there

is still ~5% to go before they actually shut off.
I know that Gellcell / NiMh / Lead Acid chargers indicate 'Fully charged'
when the battery is around 85 - 95% full.

Lots of good info on general glider wiring practices at
http://aviation.derosaweb.net/presentations/#wiring

Particularly like the bit about fusing light current wiring so that it
doesn't
go up in flames. After a bumpy landing I once had an undercarriage-
warning wire let out some smoke. It was connected to a 10 amp fused
bus. The fuse didn't blow due to the resistance of the thin wire but it
still
got very hot! Luckily it was Tefzel wire and didn't melt.

[Martin Gregorie[_6_]]

On Wed, 17 Apr 2019 18:58:38 -0700, John DeRosa OHM Ω
http://aviation.derosaweb.net wrote:

> Every year I test my two LiFePO4 batteries to gauge how long they will
> last during a flight. I decided to open the field a bit and also tested
> some soaring friend's batteries.
>
> You can read about my simple cheap manual process (later automated - see
> below) here > http://aviation.derosaweb.net/#batterytest which was also
> detailed in Soaring (Feb 2012). Yeah, I know there are automated
> testers on the market but I want to create something cheap that everyone
> can make.
>
> My battery go/no-go is how long it will take for the battery to drop to
> 12.0Vdc with a continuous 12Ω (~1A) resistive load. Here is what I
> found;
>
> 2013 Bioenno Model BLF-1209T- 6.5H 2015 Stark Model SP-12V9-EF - 5.5h
> 2015 Bioenno Model HN12V9AHF- 7.0H 2017 Bioenno model BLF-1209WS - 9.0H
>
> Full details of my results can be found here >
> http://aviation.derosaweb.net/batterytest/
Battery_Testing_Results_04.08.19.pdf
>
> Anyone else tested their batteries in this same way? What are your
> results?
>
> Automation - Manually gathering data every 10 minutes for 6-9 hours on
> four different batteries is tedious at best. I watched a lot of movies.
> So I decided to automate the process with an cheap $10 Arduino Duo.
> The Arduino software takes a reading at different points of time based
> on the current voltage. Every one minute at the beginning and end of
> the test, and every 10 minutes in the middle.
>
> It still takes 6-9 hours to run the test but recording the voltages is
> fully automated so running the test is a
> start-then-walk-away-and-come-back-later-for-the-findings kind of deal.
> Luckily with the LiFePO4 batteries when they get below ~11.0Vdc the BMS
> basically shuts the battery off. The program detects any voltage drop
> below 8Vdc and terminates itself.
>
> If anyone is interested in duplicating my Arduino test rig, drop me a
> line and I will share the details. My Arduino code can be found at
> http://aviation.derosaweb.net/batterytest/arduino.
>
I do much the same each winter, but I use an old Pro-Peak Prodigy II
battery charger/cycler mainly because I already had one, bought for model
flying. This does lead-acid, NiCd, NiMH and Li and discharges at 400 mA -
a bit low (my panel draws 480 mA excluding the radio, which is on a
second battery along with the T&B) but it does measure capacity
automatically: connect a battery, hit start and go do something else
until its finished.

You can find similar charger/cyclers on Ebay for GBP 22 ($30).

I used to run my Prodigy II off another SLA, but at some point weakened
and bought a cheapish 12 volt supply for it.


--
Martin | martin at
Gregorie | gregorie dot org

[Richard Pfiffner[_2_]]

On Wednesday, April 17, 2019 at 6:58:40 PM UTC-7, John DeRosa OHM Ω http://aviation.derosaweb.net wrote:
> Every year I test my two LiFePO4 batteries to gauge how long they will last during a flight. I decided to open the field a bit and also tested some soaring friend's batteries.
>
> You can read about my simple cheap manual process (later automated - see below) here > http://aviation.derosaweb.net/#batterytest which was also detailed in Soaring (Feb 2012). Yeah, I know there are automated testers on the market but I want to create something cheap that everyone can make.
>
> My battery go/no-go is how long it will take for the battery to drop to 12.0Vdc with a continuous 12Ω (~1A) resistive load. Here is what I found;
>
> 2013 Bioenno Model BLF-1209T- 6.5H
> 2015 Stark Model SP-12V9-EF - 5.5h
> 2015 Bioenno Model HN12V9AHF- 7.0H
> 2017 Bioenno model BLF-1209WS - 9.0H
>
> Full details of my results can be found here > http://aviation.derosaweb.net/batterytest/Battery_Testing_Results_04.08.19.pdf
>
> Anyone else tested their batteries in this same way? What are your results?
>
> Automation - Manually gathering data every 10 minutes for 6-9 hours on four different batteries is tedious at best. I watched a lot of movies. So I decided to automate the process with an cheap $10 Arduino Duo. The Arduino software takes a reading at different points of time based on the current voltage. Every one minute at the beginning and end of the test, and every 10 minutes in the middle.
>
> It still takes 6-9 hours to run the test but recording the voltages is fully automated so running the test is a start-then-walk-away-and-come-back-later-for-the-findings kind of deal. Luckily with the LiFePO4 batteries when they get below ~11.0Vdc the BMS basically shuts the battery off. The program detects any voltage drop below 8Vdc and terminates itself.
>
> If anyone is interested in duplicating my Arduino test rig, drop me a line and I will share the details. My Arduino code can be found at http://aviation.derosaweb.net/batterytest/arduino.
>
> John OHM Ω

John,

I also test my LIFEPO4 each season with a West Mountain Tester. It is connected to my laptop and produces a graph for each test I use 3 amp discharge rate. The 12V 10Ah Power Tech "Ultra Stream" Lithium Ion Battery (LiFePO4) Energy Storage Battery that I sell all tested between 9 - 10 AH. The 14Ah all tested between 13- 14 AH.

I provide a test graph with each battery I sell.

I will provide all the results in a later post.

Richard
www.craggyaero.com

[Roger Burghall[_2_]]

As I still use SLA batteries and am into that sort of thing, I designed and
built a charger/tester using a PIC microcontroller. It doesn't record graph
data as I didn't see the point, but it tops the battery up, discharges it
while monitoring the capacity, and charges it up again - or just charges it
if that is what I want. A 16 by 2 display shows what it is doing and
displays the capacity once the discharge phase is done.

If anyone wanted to copy it I would be happy to let them have the design
and software and help if needed.

[Tango Eight]

On Wednesday, April 17, 2019 at 9:58:40 PM UTC-4, John DeRosa OHM Ω
> Anyone else tested their batteries in this same way? What are your results?

I test my LFP battery annually on a cheap multimode RC battery charger with coulombmeter. My six year old Bioenno 12 AH battery is now down to 11 AH capacity.

T8

[[email protected]]

On Thursday, April 18, 2019 at 12:15:38 PM UTC-4, Tango Eight wrote:
> On Wednesday, April 17, 2019 at 9:58:40 PM UTC-4, John DeRosa OHM Ω
> > Anyone else tested their batteries in this same way? What are your results?
>
> I test my LFP battery annually on a cheap multimode RC battery charger with coulombmeter. My six year old Bioenno 12 AH battery is now down to 11 AH capacity.
>
> T8

I got the tip from T8 and got the iMax B6 charger/discharger. It is a very versatile device (multiple chemistries and voltages) and only costs about $30. The fastest it can discharge a 12-14V battery is at 0.4A due to its heat dissipation rate limit (automatically set). But that's close enough to real-life glider usage to give a good indication of the battery capacity. It's also good for charging the battery (whether SLA or LiFePO4), and every time you use it for charging you can see at what voltage it starts at and how many AH it put in by the time it ends.

[kinsell]

On 4/17/19 7:58 PM, John DeRosa OHM Ω http://aviation.derosaweb.net wrote:

> Luckily with the LiFePO4 batteries when they get below ~11.0Vdc the BMS basically shuts the battery off.
True for most of them, but some of them don't actually do that. Easy to
ruin the battery that way. If I were building a battery tester, I'd
include an automatic load cutoff.

[[email protected]]

On Thursday, April 18, 2019 at 11:09:51 PM UTC-4, kinsell wrote:
> On 4/17/19 7:58 PM, John DeRosa OHM Ω http://aviation.derosaweb.net wrote:
>
> > Luckily with the LiFePO4 batteries when they get below ~11.0Vdc the BMS basically shuts the battery off.
> True for most of them, but some of them don't actually do that. Easy to
> ruin the battery that way. If I were building a battery tester, I'd
> include an automatic load cutoff.

The "B6" device will stop the discharge at 2V per cell. That's only 8 volts for a 4-cell ("12V") battery. That's rather low, although supposedly does not harm the battery. But you can cheat and tell it it's a 5-cell battery, then it will stop at 10V. Just remember to change it to 4 cells for charging!!!

A "12V" LiFePO4 battery in good shape will maintain above or close to 12V for almost all of its discharge curve, then plummet rapidly at the end.

[2G]

On Wednesday, April 17, 2019 at 6:58:40 PM UTC-7, John DeRosa OHM Ω http://aviation.derosaweb.net wrote:
> Every year I test my two LiFePO4 batteries to gauge how long they will last during a flight. I decided to open the field a bit and also tested some soaring friend's batteries.
>
> You can read about my simple cheap manual process (later automated - see below) here > http://aviation.derosaweb.net/#batterytest which was also detailed in Soaring (Feb 2012). Yeah, I know there are automated testers on the market but I want to create something cheap that everyone can make.
>
> My battery go/no-go is how long it will take for the battery to drop to 12.0Vdc with a continuous 12Ω (~1A) resistive load. Here is what I found;
>
> 2013 Bioenno Model BLF-1209T- 6.5H
> 2015 Stark Model SP-12V9-EF - 5.5h
> 2015 Bioenno Model HN12V9AHF- 7.0H
> 2017 Bioenno model BLF-1209WS - 9.0H
>
> Full details of my results can be found here > http://aviation.derosaweb.net/batterytest/Battery_Testing_Results_04.08.19.pdf
>
> Anyone else tested their batteries in this same way? What are your results?
>
> Automation - Manually gathering data every 10 minutes for 6-9 hours on four different batteries is tedious at best. I watched a lot of movies. So I decided to automate the process with an cheap $10 Arduino Duo. The Arduino software takes a reading at different points of time based on the current voltage. Every one minute at the beginning and end of the test, and every 10 minutes in the middle.
>
> It still takes 6-9 hours to run the test but recording the voltages is fully automated so running the test is a start-then-walk-away-and-come-back-later-for-the-findings kind of deal. Luckily with the LiFePO4 batteries when they get below ~11.0Vdc the BMS basically shuts the battery off. The program detects any voltage drop below 8Vdc and terminates itself.
>
> If anyone is interested in duplicating my Arduino test rig, drop me a line and I will share the details. My Arduino code can be found at http://aviation.derosaweb.net/batterytest/arduino.
>
> John OHM Ω

It would be helpful to modify your spreadsheet to calculate watt-hours. Comparing batteries by amp-hour capacity was ok when using the same chemistry, but is not misleading when comparing SLA to LFP.

There is a marketing ploy among the LFP manufacturers called "equivalent SLA capacity." It turns out that they are using very high discharge rates (10C) to come up with this so-called "equivalent capacity." When WH capacities are compared at a more typical glider situation, 1C, the LFP has about a 7% WH advantage at the same AH rating.

The big advantage of LFP batteries is there slower aging characteristic. SLA batteries can drop precipitously after 2-3 years of use, far beyond any datasheets I have read. They *should* be good for 400-500 discharge cycles. This would be at least 10 years of typical, non-commercial glider flying. Only once have I seen SLA batteries last more than 4 years, and most are really shot by then (50% capacity).

I encourage more sharing of battery testing of this sort. It will help us get a better handle on this annoying technology which even the big boys hate (just ask Boeing).

Tom

[[email protected]]

On Sunday, April 21, 2019 at 1:56:13 AM UTC-4, 2G wrote:
> On Wednesday, April 17, 2019 at 6:58:40 PM UTC-7, John DeRosa OHM Ω http://aviation.derosaweb.net wrote:
> > Every year I test my two LiFePO4 batteries to gauge how long they will last during a flight. I decided to open the field a bit and also tested some soaring friend's batteries.
> >
> > You can read about my simple cheap manual process (later automated - see below) here > http://aviation.derosaweb.net/#batterytest which was also detailed in Soaring (Feb 2012). Yeah, I know there are automated testers on the market but I want to create something cheap that everyone can make.
> >
> > My battery go/no-go is how long it will take for the battery to drop to 12.0Vdc with a continuous 12Ω (~1A) resistive load. Here is what I found;
> >
> > 2013 Bioenno Model BLF-1209T- 6.5H
> > 2015 Stark Model SP-12V9-EF - 5.5h
> > 2015 Bioenno Model HN12V9AHF- 7.0H
> > 2017 Bioenno model BLF-1209WS - 9.0H
> >
> > Full details of my results can be found here > http://aviation.derosaweb.net/batterytest/Battery_Testing_Results_04.08.19.pdf
> >
> > Anyone else tested their batteries in this same way? What are your results?
> >
> > Automation - Manually gathering data every 10 minutes for 6-9 hours on four different batteries is tedious at best. I watched a lot of movies. So I decided to automate the process with an cheap $10 Arduino Duo. The Arduino software takes a reading at different points of time based on the current voltage. Every one minute at the beginning and end of the test, and every 10 minutes in the middle.
> >
> > It still takes 6-9 hours to run the test but recording the voltages is fully automated so running the test is a start-then-walk-away-and-come-back-later-for-the-findings kind of deal. Luckily with the LiFePO4 batteries when they get below ~11.0Vdc the BMS basically shuts the battery off. The program detects any voltage drop below 8Vdc and terminates itself.
> >
> > If anyone is interested in duplicating my Arduino test rig, drop me a line and I will share the details. My Arduino code can be found at http://aviation.derosaweb.net/batterytest/arduino.
> >
> > John OHM Ω
>
> It would be helpful to modify your spreadsheet to calculate watt-hours. Comparing batteries by amp-hour capacity was ok when using the same chemistry, but is not misleading when comparing SLA to LFP.
>
> There is a marketing ploy among the LFP manufacturers called "equivalent SLA capacity." It turns out that they are using very high discharge rates (10C) to come up with this so-called "equivalent capacity." When WH capacities are compared at a more typical glider situation, 1C, the LFP has about a 7% WH advantage at the same AH rating.
>
> The big advantage of LFP batteries is there slower aging characteristic. SLA batteries can drop precipitously after 2-3 years of use, far beyond any datasheets I have read. They *should* be good for 400-500 discharge cycles.. This would be at least 10 years of typical, non-commercial glider flying. Only once have I seen SLA batteries last more than 4 years, and most are really shot by then (50% capacity).
>
> I encourage more sharing of battery testing of this sort. It will help us get a better handle on this annoying technology which even the big boys hate (just ask Boeing).
>
> Tom

Yeah, batteries, a love-hate relationship, can't live without them, but they suck. One thing about capacities: if you fully discharge an SLA repeatedly it shortens its life (as measured in years). Thus a "9AH" SLA is really about 5AH, unless you don't care if you have to replace it in less than 2 years. (They are cheap enough that you may not care.) OTOH the LFP battery you can bring right down to where it shuts itself off and no harm done. So if it is honestly rated, a 9AH LFP truly has usable 9AH, perhaps 8AH after a few years. Just don't touch any LFP rated as "xxAH SLA equivalent", those are designed for starting motors (e.g., for motorcycles) and they are "equivalent" in cranking power (peak current) but not real AH (low current for hours).

Moreover, the voltage of the LFP stays higher (say well above 12V) for a much higher portion of its discharge cycle, then plummets. That means less warning about when it will run out, but meanwhile your radio transmissions will be good. An SLA gradually declines in voltage as it discharges, and some radios (and some other devices) may not work as well on, say, 11.7V.

Albeit most modern glider-oriented devices (e.g., varios) are designed to work normally down to 10V or so. Devices with internal switching power supplies draw more current when the supply voltage is lower, roughly a constant power draw (watts). E.g., I measured the current draw of a Portable PowerFLARM and it was roughly between 100 and 200 milliamps, depending on the supply voltage, the higher the voltage the LOWER the current (very unlike a light bulb). That's why an LFP, with its somewhat higher voltage, yields a longer run time than an SLA for the same amp-hours discharged.

[2G]

On Sunday, April 21, 2019 at 6:48:38 AM UTC-7, wrote:
> On Sunday, April 21, 2019 at 1:56:13 AM UTC-4, 2G wrote:
> > On Wednesday, April 17, 2019 at 6:58:40 PM UTC-7, John DeRosa OHM Ω http://aviation.derosaweb.net wrote:
> > > Every year I test my two LiFePO4 batteries to gauge how long they will last during a flight. I decided to open the field a bit and also tested some soaring friend's batteries.
> > >
> > > You can read about my simple cheap manual process (later automated - see below) here > http://aviation.derosaweb.net/#batterytest which was also detailed in Soaring (Feb 2012). Yeah, I know there are automated testers on the market but I want to create something cheap that everyone can make.
> > >
> > > My battery go/no-go is how long it will take for the battery to drop to 12.0Vdc with a continuous 12Ω (~1A) resistive load. Here is what I found;
> > >
> > > 2013 Bioenno Model BLF-1209T- 6.5H
> > > 2015 Stark Model SP-12V9-EF - 5.5h
> > > 2015 Bioenno Model HN12V9AHF- 7.0H
> > > 2017 Bioenno model BLF-1209WS - 9.0H
> > >
> > > Full details of my results can be found here > http://aviation.derosaweb.net/batterytest/Battery_Testing_Results_04.08.19.pdf
> > >
> > > Anyone else tested their batteries in this same way? What are your results?
> > >
> > > Automation - Manually gathering data every 10 minutes for 6-9 hours on four different batteries is tedious at best. I watched a lot of movies. So I decided to automate the process with an cheap $10 Arduino Duo. The Arduino software takes a reading at different points of time based on the current voltage. Every one minute at the beginning and end of the test, and every 10 minutes in the middle.
> > >
> > > It still takes 6-9 hours to run the test but recording the voltages is fully automated so running the test is a start-then-walk-away-and-come-back-later-for-the-findings kind of deal. Luckily with the LiFePO4 batteries when they get below ~11.0Vdc the BMS basically shuts the battery off. The program detects any voltage drop below 8Vdc and terminates itself.
> > >
> > > If anyone is interested in duplicating my Arduino test rig, drop me a line and I will share the details. My Arduino code can be found at http://aviation.derosaweb.net/batterytest/arduino.
> > >
> > > John OHM Ω
> >
> > It would be helpful to modify your spreadsheet to calculate watt-hours. Comparing batteries by amp-hour capacity was ok when using the same chemistry, but is not misleading when comparing SLA to LFP.
> >
> > There is a marketing ploy among the LFP manufacturers called "equivalent SLA capacity." It turns out that they are using very high discharge rates (10C) to come up with this so-called "equivalent capacity." When WH capacities are compared at a more typical glider situation, 1C, the LFP has about a 7% WH advantage at the same AH rating.
> >
> > The big advantage of LFP batteries is there slower aging characteristic.. SLA batteries can drop precipitously after 2-3 years of use, far beyond any datasheets I have read. They *should* be good for 400-500 discharge cycles. This would be at least 10 years of typical, non-commercial glider flying. Only once have I seen SLA batteries last more than 4 years, and most are really shot by then (50% capacity).
> >
> > I encourage more sharing of battery testing of this sort. It will help us get a better handle on this annoying technology which even the big boys hate (just ask Boeing).
> >
> > Tom
>
> Yeah, batteries, a love-hate relationship, can't live without them, but they suck. One thing about capacities: if you fully discharge an SLA repeatedly it shortens its life (as measured in years). Thus a "9AH" SLA is really about 5AH, unless you don't care if you have to replace it in less than 2 years. (They are cheap enough that you may not care.) OTOH the LFP battery you can bring right down to where it shuts itself off and no harm done. So if it is honestly rated, a 9AH LFP truly has usable 9AH, perhaps 8AH after a few years. Just don't touch any LFP rated as "xxAH SLA equivalent", those are designed for starting motors (e.g., for motorcycles) and they are "equivalent" in cranking power (peak current) but not real AH (low current for hours).
>
> Moreover, the voltage of the LFP stays higher (say well above 12V) for a much higher portion of its discharge cycle, then plummets. That means less warning about when it will run out, but meanwhile your radio transmissions will be good. An SLA gradually declines in voltage as it discharges, and some radios (and some other devices) may not work as well on, say, 11.7V.
>
> Albeit most modern glider-oriented devices (e.g., varios) are designed to work normally down to 10V or so. Devices with internal switching power supplies draw more current when the supply voltage is lower, roughly a constant power draw (watts). E.g., I measured the current draw of a Portable PowerFLARM and it was roughly between 100 and 200 milliamps, depending on the supply voltage, the higher the voltage the LOWER the current (very unlike a light bulb). That's why an LFP, with its somewhat higher voltage, yields a longer run time than an SLA for the same amp-hours discharged.

LFP batteries are not immune from accelerated degradation due complete discharge, but may be less affected than SLA. There has been a recent report about Nissan Leaf batteries losing 10% capacity per year:
file:///C:/Users/tom_s/Downloads/preprints201803.0122.v1.pdf
These cars used a nickel manganese cobalt chemistry, so is not directly applicable to LFP. I think we will have to collect the data as there is no upside for manufacturers doing it.

Most avionics are using switching power supplies, so we should be comparing batteries on the WH capacity, not AH. LFP manufacturers are using SLA AH-equivalent comparisons for energy storage applications, not starter batteries, which have markedly lower energy storage. Motorgliders are a somewhat unique situation where you would like to do both with the same battery.

Tom

[John DeRosa OHM Ω http://aviation.derosaweb.net]

Some updates;

- I was lent a Bioenno BLF-1209WS purchased in Jan 2019. Tested and ran for 8.8h.
- Updated my Arduino automated tester by adding an "LCD Keypad Shield" display to allow monitoring of the testing. The updated code has been uploaded..
- Created a new XLS spreadsheet to parse the automated testing results and create a graph from them
- Added pictures of my test rig.

Find all this, and more, at http://aviation.derosaweb.net/batterytest.

John OHM Ω

[Dan Daly[_2_]]

On Thursday, May 2, 2019 at 5:11:13 PM UTC-4, John DeRosa OHM Ω http://aviation.derosaweb.net wrote:
> Some updates;
>
> - I was lent a Bioenno BLF-1209WS purchased in Jan 2019. Tested and ran for 8.8h.
> - Updated my Arduino automated tester by adding an "LCD Keypad Shield" display to allow monitoring of the testing. The updated code has been uploaded.
> - Created a new XLS spreadsheet to parse the automated testing results and create a graph from them
> - Added pictures of my test rig.
>
> Find all this, and more, at http://aviation.derosaweb.net/batterytest.
>
> John OHM Ω

I get 404 not found at http://aviation.derosaweb.net/batterytest/Battery_Testing_Template.xls and the other two as well. I do see the SOARING reprint, though.

[John DeRosa OHM Ω http://aviation.derosaweb.net]

On Thursday, May 2, 2019 at 4:27:06 PM UTC-5, Dan Daly wrote:
> On Thursday, May 2, 2019 at 5:11:13 PM UTC-4, John DeRosa OHM Ω http://aviation.derosaweb.net wrote:
> > Some updates;
> >
> > - I was lent a Bioenno BLF-1209WS purchased in Jan 2019. Tested and ran for 8.8h.
> > - Updated my Arduino automated tester by adding an "LCD Keypad Shield" display to allow monitoring of the testing. The updated code has been uploaded.
> > - Created a new XLS spreadsheet to parse the automated testing results and create a graph from them
> > - Added pictures of my test rig.
> >
> > Find all this, and more, at http://aviation.derosaweb.net/batterytest.
> >
> > John OHM Ω
>
> I get 404 not found at http://aviation.derosaweb.net/batterytest/Battery_Testing_Template.xls and the other two as well. I do see the SOARING reprint, though.

Dan - You might just need a web page refresh as I had been actively updating the web page around the time of your 404. Let me know if it still fails.

[Dan Daly[_2_]]

On Friday, May 3, 2019 at 12:33:46 AM UTC-4, John DeRosa OHM Ω http://aviation.derosaweb.net wrote:
> On Thursday, May 2, 2019 at 4:27:06 PM UTC-5, Dan Daly wrote:
> > On Thursday, May 2, 2019 at 5:11:13 PM UTC-4, John DeRosa OHM Ω http://aviation.derosaweb.net wrote:
> > > Some updates;
> > >
> > > - I was lent a Bioenno BLF-1209WS purchased in Jan 2019. Tested and ran for 8.8h.
> > > - Updated my Arduino automated tester by adding an "LCD Keypad Shield" display to allow monitoring of the testing. The updated code has been uploaded.
> > > - Created a new XLS spreadsheet to parse the automated testing results and create a graph from them
> > > - Added pictures of my test rig.
> > >
> > > Find all this, and more, at http://aviation.derosaweb.net/batterytest..
> > >
> > > John OHM Ω
> >
> > I get 404 not found at http://aviation.derosaweb.net/batterytest/Battery_Testing_Template.xls and the other two as well. I do see the SOARING reprint, though.
>
> Dan - You might just need a web page refresh as I had been actively updating the web page around the time of your 404. Let me know if it still fails.

John - it now shows the "updated" banner, and I can download. Thank you! Your page is a great resource!

[John DeRosa OHM Ω http://aviation.derosaweb.net]

You may remember last spring that I did some testing under load of my (and others) LiFePO4 batteries. After a year's worth of soaring I tested my two batteries again. Below is an update and comparison.

Tested was done with a 1A load and after just coming off the charger to when the battery has discharged to 12Vdc.

2015 Stark - Model SP-12V9-EF
April 2019 - 5.71h
October 2019 - 5.49h (loss of 13.3mins or 3.8%)
2017 Bioenno - Model BLF-1209WS
April 2019 - 8.83H
October 2019 - 8.85h (loss of 12.0mins or 3.2%)

I also updated my Arduino based testing rig's display. Previously, I used a simple 2 line by 16 character LCD B/W display. Now I am using a 240x320 pixel LCD touch sensitive color display. Oooooo, cool (and surprisingly cheap).

The new display allows me more room to display information during testing and to create a real time graph of the data. Displays are more fun than necessary but what the heck. There is amazingly inexpensive open-source hardware available for the Arduino system. The O'Reilly "Arduino Cookbook" leads you by the hand to create some powerful cool tools.

Information can be found at http://aviation.derosaweb.net/presentations/#batterytest.

[2G]

On Thursday, May 2, 2019 at 2:11:13 PM UTC-7, John DeRosa OHM Ω http://aviation.derosaweb.net wrote:
> Some updates;
>
> - I was lent a Bioenno BLF-1209WS purchased in Jan 2019. Tested and ran for 8.8h.
> - Updated my Arduino automated tester by adding an "LCD Keypad Shield" display to allow monitoring of the testing. The updated code has been uploaded.
> - Created a new XLS spreadsheet to parse the automated testing results and create a graph from them
> - Added pictures of my test rig.
>
> Find all this, and more, at http://aviation.derosaweb.net/batterytest.
>
> John OHM Ω

Congratulations on building a battery tester (I wouldn't bother, myself).

But here are the shortcomings of your tester:
1. It has no discharge cutoff. It keeps discharging the battery until totally discharged. This can damage the battery, and is certainly not good for it. I would not test a battery w/o this.

2. It does not discharge at a constant current. The current decreases as the voltage drops. Modern battery testers will do this.

3. It does not discharge at a constant wattage. This is a more typical scenario where avionics will increase current as the voltage drops.

That said, it is better than sitting down for 6 to 10 hours and recording meter readings. I have switched my avionics battery from a Pb to a LiFePO4 partly because I don't want to buy a new battery every 2 years.

Tom

[krasw]

On Wednesday, 16 October 2019 05:44:35 UTC+3, 2G wrote:
> On Thursday, May 2, 2019 at 2:11:13 PM UTC-7, John DeRosa OHM Ω http://aviation.derosaweb.net wrote:
> > Some updates;
> >
> > - I was lent a Bioenno BLF-1209WS purchased in Jan 2019. Tested and ran for 8.8h.
> > - Updated my Arduino automated tester by adding an "LCD Keypad Shield" display to allow monitoring of the testing. The updated code has been uploaded.
> > - Created a new XLS spreadsheet to parse the automated testing results and create a graph from them
> > - Added pictures of my test rig.
> >
> > Find all this, and more, at http://aviation.derosaweb.net/batterytest.
> >
> > John OHM Ω
>
> Congratulations on building a battery tester (I wouldn't bother, myself).
>
> But here are the shortcomings of your tester:
> 1. It has no discharge cutoff. It keeps discharging the battery until totally discharged. This can damage the battery, and is certainly not good for it. I would not test a battery w/o this.
>
> 2. It does not discharge at a constant current. The current decreases as the voltage drops. Modern battery testers will do this.
>
> 3. It does not discharge at a constant wattage. This is a more typical scenario where avionics will increase current as the voltage drops.
>
> That said, it is better than sitting down for 6 to 10 hours and recording meter readings. I have switched my avionics battery from a Pb to a LiFePO4 partly because I don't want to buy a new battery every 2 years.
>
> Tom

1. BMS does the cutoff inside battery anyway
2. Voltage does not drop much with LFP
3. How is this relevant, most just want to know if their battery capacity is 10Ah or 7 Ah, not 9.998 Ah.

[[email protected]]

John,

Thanks for the yearly update on how your batteries are ageing. It's nice to see what they do under constant test conditions. (I did get a 404 not found on your 2019 pdf file link?)

In (one of)2G's directions, the modern cockpit does have those pesky switchers. I wonder if an easy alternative load might be some 12 -> 5v usb chargers with light bulb loads on the 5v side. The computer rig could watch V&I on the battery side and especially the time till the BMS says lights out.

Not all K2's are the same. I have 4 of 2 different ages. One of them seems a little more tired than the others. This prompted me to setup a more complicated rig.

Depending on that the VHF and transponder are doing, one K2 will keep my bus up for around 4 hours. I added a second in parallel with it thru a low drop diode. The hope was that this would keep the batteries from circulating current, and make it about 2x longer before lights out, and let me see the switchover as the bus drops 0.4v, and work with the SH battery in parallel wiring. So far, so good. It's lasted longer than I have without needing to switch to the third, get home battery.

One of these days, I need to get around to trying them with your test plan.

Thanks again,
Stu

[kinsell]

On 10/16/19 4:05 AM, krasw wrote:
> On Wednesday, 16 October 2019 05:44:35 UTC+3, 2G wrote:
>> On Thursday, May 2, 2019 at 2:11:13 PM UTC-7, John DeRosa OHM Ω http://aviation.derosaweb.net wrote:
>>> Some updates;
>>>
>>> - I was lent a Bioenno BLF-1209WS purchased in Jan 2019. Tested and ran for 8.8h.
>>> - Updated my Arduino automated tester by adding an "LCD Keypad Shield" display to allow monitoring of the testing. The updated code has been uploaded.
>>> - Created a new XLS spreadsheet to parse the automated testing results and create a graph from them
>>> - Added pictures of my test rig.
>>>
>>> Find all this, and more, at http://aviation.derosaweb.net/batterytest.
>>>
>>> John OHM Ω
>>
>> Congratulations on building a battery tester (I wouldn't bother, myself).
>>
>> But here are the shortcomings of your tester:
>> 1. It has no discharge cutoff. It keeps discharging the battery until totally discharged. This can damage the battery, and is certainly not good for it. I would not test a battery w/o this.
>>
>> 2. It does not discharge at a constant current. The current decreases as the voltage drops. Modern battery testers will do this.
>>
>> 3. It does not discharge at a constant wattage. This is a more typical scenario where avionics will increase current as the voltage drops.
>>
>> That said, it is better than sitting down for 6 to 10 hours and recording meter readings. I have switched my avionics battery from a Pb to a LiFePO4 partly because I don't want to buy a new battery every 2 years.
>>
>> Tom
>
> 1. BMS does the cutoff inside battery anyway

Unfortunately, not all LFP batteries have a BMS, and of those that do,
not all have low-voltage cutoff. Of all the misinformation that gets
spead about on LFP's, that right at the top of the list.

Given how easy it is to add a low-side power switch, I wonder why you
would build an automated, computer controlled tester that lacks this.
Adding it would make it useful for a wide range of batteries.

[John DeRosa OHM Ω http://aviation.derosaweb.net]

On Wednesday, October 16, 2019 at 7:51:15 PM UTC-5, kinsell wrote:
>
> Unfortunately, not all LFP batteries have a BMS, and of those that do,
> not all have low-voltage cutoff. Of all the misinformation that gets
> spead about on LFP's, that right at the top of the list.
>
> Given how easy it is to add a low-side power switch, I wonder why you
> would build an automated, computer controlled tester that lacks this.
> Adding it would make it useful for a wide range of batteries.

Kinsell - You have me thinking now.

While both my Stark and Bioenno batteries has a BMS that cuts off at 10Vdc, it wouldn't be too difficult to add an Arduino relay shield to the mix. It could remove the load for non-BMS lithium batteries and for SLA's.

These shields contain four 3A 24Vac relays and cost about $4.50 (cheap! see https://www.ebay.com/itm/323801575423). The neat thing about these shields is that they stack and make a nice tidy package. I would have a stack of;

LCD Display
-----------
Relay Shield
-----------
Arduino

Once the battery charge drops to the low volt trigger point, I would remove the load (turn off the relay) from the battery via coding. One relay rated at 3A should be ok but I might use two relays in parallel to be sure.

I just ordered a couple of the relay shields and will report back.

[Charlie Quebec]

It’s 2G he has to whine and contradict people, it’s all he has got.

[2G]

On Wednesday, October 16, 2019 at 3:05:58 AM UTC-7, krasw wrote:
> On Wednesday, 16 October 2019 05:44:35 UTC+3, 2G wrote:
> > On Thursday, May 2, 2019 at 2:11:13 PM UTC-7, John DeRosa OHM Ω http://aviation.derosaweb.net wrote:
> > > Some updates;
> > >
> > > - I was lent a Bioenno BLF-1209WS purchased in Jan 2019. Tested and ran for 8.8h.
> > > - Updated my Arduino automated tester by adding an "LCD Keypad Shield" display to allow monitoring of the testing. The updated code has been uploaded.
> > > - Created a new XLS spreadsheet to parse the automated testing results and create a graph from them
> > > - Added pictures of my test rig.
> > >
> > > Find all this, and more, at http://aviation.derosaweb.net/batterytest..
> > >
> > > John OHM Ω
> >
> > Congratulations on building a battery tester (I wouldn't bother, myself).
> >
> > But here are the shortcomings of your tester:
> > 1. It has no discharge cutoff. It keeps discharging the battery until totally discharged. This can damage the battery, and is certainly not good for it. I would not test a battery w/o this.
> >
> > 2. It does not discharge at a constant current. The current decreases as the voltage drops. Modern battery testers will do this.
> >
> > 3. It does not discharge at a constant wattage. This is a more typical scenario where avionics will increase current as the voltage drops.
> >
> > That said, it is better than sitting down for 6 to 10 hours and recording meter readings. I have switched my avionics battery from a Pb to a LiFePO4 partly because I don't want to buy a new battery every 2 years.
> >
> > Tom
>
> 1. BMS does the cutoff inside battery anyway
> 2. Voltage does not drop much with LFP
> 3. How is this relevant, most just want to know if their battery capacity is 10Ah or 7 Ah, not 9.998 Ah.

1. No, the BMS will not cutoff discharge - I know.
2. Relevant when comparing different battery chemistry's.
3. It's relevant when comparing lithium batteries to lead-acid.

As a former electrical engineer, I strove to minimize error sources as much as feasible because until you know the answer, you don't know which error is going to bite you in the butt. Nothing worse than having your glass panel go dark in the middle of nowhere because you under-estimated.

Tom

[2G]

On Wednesday, October 16, 2019 at 7:25:24 PM UTC-7, Charlie Quebec wrote:
> It’s 2G he has to whine and contradict people, it’s all he has got.

CQ, go **** off...

[kinsell]

On 10/16/19 7:40 PM, John DeRosa OHM Ω http://aviation.derosaweb.net wrote:
> On Wednesday, October 16, 2019 at 7:51:15 PM UTC-5, kinsell wrote:
>>
>> Unfortunately, not all LFP batteries have a BMS, and of those that do,
>> not all have low-voltage cutoff. Of all the misinformation that gets
>> spead about on LFP's, that right at the top of the list.
>>
>> Given how easy it is to add a low-side power switch, I wonder why you
>> would build an automated, computer controlled tester that lacks this.
>> Adding it would make it useful for a wide range of batteries.
>
> Kinsell - You have me thinking now.
>
> While both my Stark and Bioenno batteries has a BMS that cuts off at 10Vdc, it wouldn't be too difficult to add an Arduino relay shield to the mix. It could remove the load for non-BMS lithium batteries and for SLA's.
>
> These shields contain four 3A 24Vac relays and cost about $4.50 (cheap! see https://www.ebay.com/itm/323801575423). The neat thing about these shields is that they stack and make a nice tidy package. I would have a stack of;
>
> LCD Display
> -----------
> Relay Shield
> -----------
> Arduino
>
> Once the battery charge drops to the low volt trigger point, I would remove the load (turn off the relay) from the battery via coding. One relay rated at 3A should be ok but I might use two relays in parallel to be sure.
>
> I just ordered a couple of the relay shields and will report back.
>

Good, that would be a nice addition to your project. You can also
Google "low-side power mosfets" for a different option that takes less
power to drive. Probably available in a stackable module also.

[krasw]

On Thursday, 17 October 2019 03:51:15 UTC+3, kinsell wrote:
> On 10/16/19 4:05 AM, krasw wrote:
> > On Wednesday, 16 October 2019 05:44:35 UTC+3, 2G wrote:
> >> On Thursday, May 2, 2019 at 2:11:13 PM UTC-7, John DeRosa OHM Ω http://aviation.derosaweb.net wrote:
> >>> Some updates;
> >>>
> >>> - I was lent a Bioenno BLF-1209WS purchased in Jan 2019. Tested and ran for 8.8h.
> >>> - Updated my Arduino automated tester by adding an "LCD Keypad Shield" display to allow monitoring of the testing. The updated code has been uploaded.
> >>> - Created a new XLS spreadsheet to parse the automated testing results and create a graph from them
> >>> - Added pictures of my test rig.
> >>>
> >>> Find all this, and more, at http://aviation.derosaweb.net/batterytest..
> >>>
> >>> John OHM Ω
> >>
> >> Congratulations on building a battery tester (I wouldn't bother, myself).
> >>
> >> But here are the shortcomings of your tester:
> >> 1. It has no discharge cutoff. It keeps discharging the battery until totally discharged. This can damage the battery, and is certainly not good for it. I would not test a battery w/o this.
> >>
> >> 2. It does not discharge at a constant current. The current decreases as the voltage drops. Modern battery testers will do this.
> >>
> >> 3. It does not discharge at a constant wattage. This is a more typical scenario where avionics will increase current as the voltage drops.
> >>
> >> That said, it is better than sitting down for 6 to 10 hours and recording meter readings. I have switched my avionics battery from a Pb to a LiFePO4 partly because I don't want to buy a new battery every 2 years.
> >>
> >> Tom
> >
> > 1. BMS does the cutoff inside battery anyway
>
> Unfortunately, not all LFP batteries have a BMS, and of those that do,
> not all have low-voltage cutoff. Of all the misinformation that gets
> spead about on LFP's, that right at the top of the list.
>
> Given how easy it is to add a low-side power switch, I wonder why you
> would build an automated, computer controlled tester that lacks this.
> Adding it would make it useful for a wide range of batteries.

I have built tester that uses coulometer and low voltage switch, I have a car tail light bulb as a load (10 or 20W). Parts for this can be bought from ebay for next to nothing. Search ebay for "battery coulometer" and "DC12V Battery Low Voltage Automatic Cut off Controller". You get automatically reading for your battery capacity. Mine can be installed between charger and battery so that you can also read how much capacity was charged.

[Tango Eight]

My latest $0.02 on topic...

Bought a Bioenno BLF-1209WS (9 AH rated) in August, and it delivered 10.2 AH on an Imax battery charger (discharge @ 400 mA). It was still at 12V when I terminated the test for reasons not related to the battery.

T8

[John DeRosa OHM Ω http://aviation.derosaweb.net]

T8,

Thanks for the data point. To compare apples to apples it would be interesting to test connected to a 12ohm load as I did - not that 12ohms (~1A) is somehow perfection.

Thanks, John OHM

[Mike N.]

Just a suggestion but you might want to look at the following.
https://www.skyrc.com/BD200

Allows you to set discharge current and cut off voltage. Displays consumed mAh over discharge period.

You do have to calculate the cut off voltage per battery type X cells in series. There are many articles (and debates) on safe dishcharge cutoff voltages for various lithium batteries chemistries on line so I am not going to make a suggestion as to cut off voltage.

I just wanted to suggest the above tool as I find it useful. I fly very large scale R.C. helicopters which use rather large battery packs at high discharge currents and I find the above very useful for analyzing my packs.
YMMV

[Tango Eight]

The only reason for selecting 400 mA discharge is that is as much current as my little Imax RC battery charger can sink.

400mA vs 1 A is not quite apples/apples, agreed, but for LFP batteries it's going to be very close.

T8