Test results LiFePO4 glider batteries after 6 years

[SF]

I started using K2 LiFeP04 batteries in my glider in 2010. I have had excellent results with these batteries. The electronics, especially the radio, enjoy staying above 12V, and I've never run out of power inflight with them.

This winter after taking some of the instruments out to have them calibrated & upgraded, I took one of these batteries with me to the shop to power everything up to see if all the magic smoke remained in the equipment after it was reinstalled. Imagine my surprise when nothing came on, and I found the battery at 10.5 volts.

This battery was charged after its last usage 1-1/2 months ago and left in a cabinet. Since these batteries are not supposed to self discharge that fast I decided to charge, and test them using two batteries in parallel on a 2.04A load. My six year old 9.6AH K2's were down to 5.4 Ah each, 10.8 Ah total.

I purchased two new Stark Power SP-12V9-EP LiFeP04 batteries and wired them in parallel on the same 2.04A load, and got 8.67 Ah each, 17.34 Ah total.

The tests were run until the voltage under load dropped to 11.5 V, not the 10.5V level where the battery management board turns off the output. There are probably some additional Ah's left in there after 11.5 V but not much, these batteries drop off pretty fast after 12.5V. The stark batteries are listed at 9Ah each.

The LiFePO4 batteries are advertised as having a cycle life of >2,000 cycles. Over the six years they were in use, I probably put less than 400 cycles on these. So obviously they also degrade with age and not just the number of charge/discharge cycles.

I still recommend these over the old sealed lead acid batteries. I also advocate annual testing to see if they still have the capacity you need, rather than waiting until they surprise you in flight.

SF

[John Carlyle]

Curious about the cabinet you keep the batteries in. Is it in a controlled temperature space, or in an out building?

-John, Q3

[SF]

My battery cabinet is in my home office. 65-80F, Depending on Spousal override.

[cjlbo...@gmail.com]

Hi SF,

What do you use for capacity testing your batteries? Do you happen to have a link that refers? Many thanks.

CJ

[John Carlyle]

Thanks! That matches the conditions for the storage of my Bioenno BLF-1209T LiFePo4 batteries. They recommend that you store them with 50% charge, but I've been putting them away fully charged. I wonder how much of an effect that has on their life expectancy?

-John, Q3

[Tango Eight]

I guess this is the weekend to test batteries.

I have four seasons on my Bioenno 12AH LFP battery. It's down to 11.48 AH now, down from 12.05 last year and 12.1 when new. All measurements from an el cheapo imax B6 battery charger. For testing purposes I discharge to 11 volts. There is very little capacity remaining at that point.

With few exceptions, this battery has been stored with full charge.

best,
Evan Ludeman / T8

[John Carlyle]

T8, you're the reason I went with the Bioenno batteries. After reading the docs you posted, it seemed like the best value for money. Glad to hear that they're holding up for you. Do you know roughly how many charge cycles you have on them?

-John, Q3

[Steve Koerner]

SF: Last spring I charged up my 2 year old K2 batteries after about 3 months off the charger and then tested them. I was quite surprised that my capacities had dropped to a range of 2 to 3 AH over the winter period. I too had stored my batteries indoors and fully charged before I'd unplugged them over the winter period.

I got in communication with a factory engineer. The engineer had me do a couple cycles of discharge and long time charging -- on float for 10 days. His explanation was something about rebalancing the cells. I don't entirely understand the issue. Yet doing as he directed did bring my capacity back up to 8.5 AH. They worked fine all season.

Your situation sounds so similar that I'd suggest trying the same. Let us know if it fixes your K2s.

[Tango Eight]

On Sunday, January 29, 2017 at 4:50:54 PM UTC-5, John Carlyle wrote:
> T8, you're the reason I went with the Bioenno batteries. After reading the docs you posted, it seemed like the best value for money. Glad to hear that they're holding up for you. Do you know roughly how many charge cycles you have on them?
>
> -John, Q3

Call it 150 cycles to 1/2 charge on average.

T8

[John Carlyle]

Thanks, T8. I've got about the same usage to the same level. Guess I should check my remaining capacity, too.

-John, Q3

[SF]

How I test my batteries

Equipment - (1) Multimeter good for measuring up to 10A DC Current, and DC Voltage.
- (1) 2 x 6 with (4) side marker lights mounted and wired in parallel. (not LED lights, the old fashioned lights) Not wired in series either want to avoid the one goes out, they all go out Christmas Light problem. Style points awarded for the mad scientist steam punk look of the test rig.

I put one battery in the glider, set the multimeter for current put it in series with the battery, turn everything on and measure the glider's normal amp draw, then push the radio's transmit button and get that current draw.

When you are finished with that, hook the battery and the multimeter still measuring current up to your side marker lights. Add or remove bulbs until you get the desired current draw. My choice is above your gliders normal load and below the radio transmit current draw. Don't over think it, sorta close is good enough.

Get the multimeter out of the circuit. Immediately change it back to its measuring voltage configuration. Or skip this step and find out which fuse your meter uses, and what store sells them (it will be closed when this happens or currently out of stock for this size fuse). If you have a meter without a fuse in the current circuit, take a hammer to it, smash it to bits, and go out and buy one with a fuse. I saw one of those blow up one time (480V), it wasn't pretty, and there were a lot of reports to fill out afterwards.

After fully charging the Battery(s) I hook them up to the lights, measure the voltage under load every half hour and write the numbers down until it drops to 11.5 volts. Near the end you may want to check on it more often. Just for fun use the timer on the stove and drive your wife crazy for the better part of the day. Or take it to work and explain to everyone what those red lights are for in your office, or the bomb squad, if you don't catch everybody with the explanation, and leave it unattended with the door open.

Amps X Hours of run time = Ah

SF

[SF]

I'll give that a try, might save the K2's from the recycling bin

Scott

[jfitch]

The types of cell balancing used in these cheaper batteries requires getting to a fairly high charge voltage for awhile to work. If you just plug them in (or into a lower voltage charge) until the green light comes on and then unplug, the cells may never get balanced. More expensive batteries than we typically use have active cell balancing and don't require this. Li batteries are much more susceptible to cell balance issues than LA batteries, because you can just overcharge LA batteries to balance (an "equalizing" charge). Li cells have to be protected from both over charge and over discharge, so you can only charge to 100% of the best cell, and only discharge to 0 or maybe 10% of the weakest cell. As they get further out of balance with time and cycles, the apparent capacity goes down far more than the real capacity.

The 3000 cycles noted by many manufacturers refers to the cells under ideal circumstances. In a cheap battery with a cheap BMS and a cheap charger, you might not achieve the ideal.

[clewi...@gmail.com]

> How I test my batteries

Thanks Scott

[Richard]

On Sunday, January 29, 2017 at 6:31:39 PM UTC-8, clewi...@gmail.com wrote:
> > How I test my batteries
>
> Thanks Scott

I test my LiFe batteries with a West Mountain Radio CBA IV. It gives a nice graph of the discharge.

I also run a discharge and include a graph with each battery I sell. I have found some of the Batteries mentioned in this group do not meet the specs direct from the manufacturer.

Richard
www.craggyaero.com
www.craggyaero.com

[dar...@pepperdata.com]

I'd also vote for a West Mountain Radio CBA tester. They are a great thing for a club/FBO to purchase. And use it to discharge test every battery at least once per season. And write the date/results on the battery or make up a label and stick on the battery.

http://www.westmountainradio.com/cba.php

$160 very well spent.

And they can be used to test solar panels. handy for folks who have on-glider or on-trailer solar panels etc.

[Charlie M. (UH & 002 owner/pilot)]

I think it would also be good to record ambient temperature of your test area when doing a capacity test. If it's always say 70*F +/- 3*F, then temperature is not a factor in AH.
A AH test in a 50*F area will yield a different AH value than a 80*F area. I know I can find a "temp compensation chart" for LA batteries pretty quick, not sure about LiFe batteries.

Same goes for charging, temp of the batteries have an effect on charge voltage and charge rate. In LA batteries, it's the inverse of temperature, I will assume LiFe is the same.

[kevi...@gmail.com]

On Sunday, January 29, 2017 at 2:41:07 PM UTC-5, SF wrote:

> I started using K2 LiFeP04 batteries in my glider in 2010. I have had excellent results with these batteries. The electronics, especially the radio, enjoy staying above 12V, and I've never run out of power inflight with them.

Were you using the charger from K2, or another charger?

Kevin
92

[SF]

I was using a charger from K2

[cliff...@gmail.com]

Anybody tried Dakota Lifepo4 batteries? They are about $30 less than K2 and they charger is only $16.

[lmurra...@gmail.com]

This is an interesting string and it would be good to see a summary in SOARING sometime. I see that the RC community uses chargers that balance each cell in the pack. I go through RC LiPo batteries in a few years. I fear that they are going to develop a problem and cause a fire.

I don't see that cell balancing feature in the simple batteries being sold to replace the LA gel cell batteries. I think I'll sit on the side lines a little longer.
Lee Murray

[Charlie M. (UH & 002 owner/pilot)]

Some of these newer packs have the balancing/charge board internal the case, thus you don't see it.

Yes, I'm into electric RC and most of my LiPo packs have an external cell connection that plugs into the charger balancing port.

[SF]

The K2 batteries purchased 6 years ago, and the Stark Power Systems Batteries that I replaced the K2's with both have internal battery management boards in them that are supposed to prevent under discharge, over charging, and provide cell balancing. The Stark battery pricing on their website is exceptionally attractive right now. However I can't guarantee that they are any better or worse than any of the other batteries of this type currently for sale.

Someone else in this thread mentioned that these boards do not do quite as good a job at cell balancing as what is normally used on a much more expensive battery packs, and that they need an extended period on float charge to re-balance.

Currently I have discharged the K2's and they are now on extended "float" charging to see if the cells re-balance after several days on float.

I don't have a lot of hope for the re balancing attempt. The discharge graph for the K2's in their current condition isn't typical for Lithium batteries. It looks more like the typical SLA battery discharge graph. In my professional opinion some of the magic smoke came out, and as we all know that just never goes back in again.

The point of all this was to give everyone a heads up that these things don't appear to last forever. I got 6 years out of them, and that's not too bad for a battery.

The Mountain Radio battery tester is a neat looking piece of equipment, but it lacks the mad scientist look of the six marker lights screwed down to a 2 x 6. Don't discount the entertainment value of aggravating everyone in the house when the timer on the stove goes off every thirty minutes during the testing either.

SF

[Matt Herron Jr.]

There is another advantage to using the dual diode method for multiple batteries. You can mix chemistries without concern. for example I have 2 LiFePo4 packs and 2 gel cells. I can use a gel and a LiFePo4 on the same flight. Power is simply drawn from the pack with the highest voltage, until both are depleted. You can't do this if you wire the batteries together directly. You can, if you use two switches of course, but you run the risk of voltage spikes or drop outs on switch over. You also don't have to monitor voltage for when to switch from one to the other as no switching is needed.

I also second automotive blade fuses at the battery terminals. Additionally I use screw-type battery connectors (3 conductor type) as they are robust and lock in place with the threaded ring.

Matt H
.

[bumper]

The CTC batteries I bought from:

http://www.batterypete.com/batteries/ctc-12-8v-19-8ah-253-44wh-lithium-battery-lfp128198/

This battery doesn't have a discrete cell balance plug, though they do have an on-board BMS and are rated for enough surge/duration current to handle engine start.

The balance/charger uses a pulsed low current for cell balance. The pulsed current allows the charger to continue to charge any "high" cells without risk of overheat/damage while bringing up low cells. That's the plan anyway. I hope.

bumper

[glidergreg]

On Sunday, January 29, 2017 at 1:41:07 PM UTC-6, SF wrote:

I switched to LiFepo4 several years ago, have a 9Amp for the transponder and a 15Amp for everything else. Great battery, never have had a problem and never ran out of juice, got them from the manufacture but Cumulus also sells them. they also sell a charger for not much more $112.00 for both. Product link https://www.bioennopower.com/collections/12v-series-lifepo4-batteries/products/12v-9ah-lfp-battery-abs-sealed-green-case-1

[Richard]

Greg,

Have you checked the batteries this is one of the manufacturers I mentioned in a previous post about specifications.

Richard.

[jfitch]

On Sunday, January 29, 2017 at 11:41:07 AM UTC-8, SF wrote:
> I started using K2 LiFeP04 batteries in my glider in 2010. I have had excellent results with these batteries. The electronics, especially the radio, enjoy staying above 12V, and I've never run out of power inflight with them.
>
> This winter after taking some of the instruments out to have them calibrated & upgraded, I took one of these batteries with me to the shop to power everything up to see if all the magic smoke remained in the equipment after it was reinstalled. Imagine my surprise when nothing came on, and I found the battery at 10.5 volts.
>
> This battery was charged after its last usage 1-1/2 months ago and left in a cabinet. Since these batteries are not supposed to self discharge that fast I decided to charge, and test them using two batteries in parallel on a 2.04A load. My six year old 9.6AH K2's were down to 5.4 Ah each, 10.8 Ah total.
>
> I purchased two new Stark Power SP-12V9-EP LiFeP04 batteries and wired them in parallel on the same 2.04A load, and got 8.67 Ah each, 17.34 Ah total.
>
> The tests were run until the voltage under load dropped to 11.5 V, not the 10.5V level where the battery management board turns off the output. There are probably some additional Ah's left in there after 11.5 V but not much, these batteries drop off pretty fast after 12.5V. The stark batteries are listed at 9Ah each.
>
> The LiFePO4 batteries are advertised as having a cycle life of >2,000 cycles. Over the six years they were in use, I probably put less than 400 cycles on these. So obviously they also degrade with age and not just the number of charge/discharge cycles.
>
> I still recommend these over the old sealed lead acid batteries. I also advocate annual testing to see if they still have the capacity you need, rather than waiting until they surprise you in flight.
>
> SF

Cell balancing in Li battery packs is either passive or active (I guess the modern terms are dissipative and non-dissipative). Either strategy can have several topologies. The cheap battery packs we buy are almost sure to be passive. They attempt to achieve balance by shunting a parallel power dissipating resistor across the high cells. It can only do this near the top of the charge cycle, and the capacity of the shunting element is small (a few milliamps) or it will burn up. That means you need to be at the top of the charge cycle for long period to complete the process. The hope is that the low cells will continue to charge while the high cells are prevented from overcharge by the shunting resistor.

One problem with a $20 charger is that it is likely to be a simple 14.6V voltage source, and some of them shut down when they hit that voltage (LiFePO4 cells should not be "float" charged, generally). If the charger shuts off or cuts back its voltage, there may not be sufficient voltage or time to charge the weak cells. There are further limitations to the technique, as they are balancing based on voltage and not capacity. These are just the cost limitations that we are dealing with. Make sure your charger maintains the 14.6 voltage on the battery for the period you think it is supposed to be balancing.

Expensive batteries will have active cell balancing, this is DC-DC convertors for each cell that take energy from strong cells and transfer it to weak ones, both during charge and discharge. Expensive battery chargers will also monitor each cell, and actively charge weak cells more. The price point for these features is higher than most glider pilots (who are cheap bastards) are willing to pay.

Maybe someone with more knowledge will chime in, but that is my understanding from looking at LiFePo4 batteries for my boat - we are talking there about $10K and up battery packs with passive, active, and charger regulated cell balancers, sometimes all at once.

[jfitch]

On Sunday, January 29, 2017 at 11:41:07 AM UTC-8, SF wrote:
> I started using K2 LiFeP04 batteries in my glider in 2010. I have had excellent results with these batteries. The electronics, especially the radio, enjoy staying above 12V, and I've never run out of power inflight with them.
>
> This winter after taking some of the instruments out to have them calibrated & upgraded, I took one of these batteries with me to the shop to power everything up to see if all the magic smoke remained in the equipment after it was reinstalled. Imagine my surprise when nothing came on, and I found the battery at 10.5 volts.
>
> This battery was charged after its last usage 1-1/2 months ago and left in a cabinet. Since these batteries are not supposed to self discharge that fast I decided to charge, and test them using two batteries in parallel on a 2.04A load. My six year old 9.6AH K2's were down to 5.4 Ah each, 10.8 Ah total.
>
> I purchased two new Stark Power SP-12V9-EP LiFeP04 batteries and wired them in parallel on the same 2.04A load, and got 8.67 Ah each, 17.34 Ah total.
>
> The tests were run until the voltage under load dropped to 11.5 V, not the 10.5V level where the battery management board turns off the output. There are probably some additional Ah's left in there after 11.5 V but not much, these batteries drop off pretty fast after 12.5V. The stark batteries are listed at 9Ah each.
>
> The LiFePO4 batteries are advertised as having a cycle life of >2,000 cycles. Over the six years they were in use, I probably put less than 400 cycles on these. So obviously they also degrade with age and not just the number of charge/discharge cycles.
>
> I still recommend these over the old sealed lead acid batteries. I also advocate annual testing to see if they still have the capacity you need, rather than waiting until they surprise you in flight.
>
> SF

Here is a decent explanation for those interested, from one of the vendors of the technology:

http://www.ti.com/lit/an/slyt322/slyt322.pdf

[jave...@gmail.com]

On Sunday, January 29, 2017 at 4:42:57 PM UTC-5, Tango Eight wrote:
> I guess this is the weekend to test batteries.
>

> I have four seasons on my Bioenno 12AH LFP battery. It's down to 11.48 AH >now, down from 12.05 last year and 12.1 when new. ...


T8-

Your battery seems to be holding up well. I also have a K2 battery that after 2 seasons is showing similar loss of capacity as SF and Steve Koerner describe. Its down to about 60% capacity. I am currently trying the extended charge cycle Steve described. I charge it with a 14.6V 2A switching charger made by Fuyuan - model FY1502000; bought it with the battery. Not sure that the charger would make that much difference if the voltage is adequate, but what type of charger do you routinely use to charge your Bioenno LFP battery? Perhaps the Bioenno has better cell balancing algorithm/hardware? I stored it at approximately half charge in the off season and always took it home for recharging when not flying.
Since I am in the market for a second LFP, trying to decide which brand to go with.

Thanks

[Richard]

I think you guys have a large dose of Hopeful.

All the batteries mentioned in this post including the BMS are made and sealed as a unit in China.

Just because you pay extra does not mean you get a better battery.

I got a batch of one of the above mentioned batteries that advertised 9 aH but only got 5 or 6 aH. They company did replace the low specification batteries when I complained.

The other issue you have is if power is reversed when charging or using the battery you will likely damage the battery or the BMS even if fused.

Richard
www.craggyaero.com

[Tango Eight]

I have the same charger, which is what Bioenno sold me with the battery.

-T8

[Jim White]

At 01:55 07 February 2017, Richard wrote:
>
>I think you guys have a large dose of Hopeful.
>
>All the batteries mentioned in this post including the BMS are made and

>sea=
>led as a unit in China. =20
>
Is that true od A123? The manufacturer claims that the design (and original
build) is American, the chemistry is failsafe, and that the BMS balances
each cell individually without needing to be on a charger.

The downside is that they also claim 5AH. I have been using these with
great results for 2 seasons now.

I also like the internal fuse feature.

Jim

[dvmar...@gmail.com]

I got the West Mountain Radio tester and ran my three K2 Energy 9.6 AH (two years old) One tested at 8.7 AH, the next at 8.5 AH, and the final one 7.3 AH. They are all charged using a dedicated LIFEPO4 charger. Not sure why the one should have so much less capacity. I will be giving K2 a call.

David
ASG29E BV

[Tom Kelley #711]

What voltage are they showing when they come off these chargers?

Best. Tom.

[dvmar...@gmail.com]

I set the tester to cut off at 11 volts. At that point the voltage is dropping rapidly as is normal with the LIFEPO4's.

David
ASG29E BV

[dvmar...@gmail.com]

Misread you question. When coming off the charger they show 14 or a bit more volts. When put on the tester that voltage drops almost immediately to 12.5 volts and then stays there till it drops off rapidly at the end of the test cycle.

David
ASG29E BV

[Tom Kelley #711]

Thanks David, bring your tester and park again in Perry where I can use your water supply, please.

Below are several notes I found on LifePO4's:

The LiFePO4 batteries exhibit slightly different properties: They have a bit lower operating voltage of about 3.2V – 3.3V, the minimum discharge voltage is 2.8V and the maximum charged voltage is 3.6V. The LiFePO4 is a kind of Li-Ion rechargeable battery intended for high power applications, such as EV cars , eBikes, electric bike, Power Tools and RC hobby.
The LiFePO4 batteries have more constant discharge voltage and are considered to offer better safety than other Lithium-based batteries. Other advantages of the Lithium-based rechargeable batteries include the ability of a much faster recharge and higher discharge rates than other chemistries mentioned and usually higher number of recharge cycles (>20...@0.2C rate, IEC Standard) , meaning longer life when not fully discharged, but its energy density is lower than normal Li-Ion cell (Li-Co)

LiFePO4 life expectancy is approximately 5-7 years.

It’s important to use a LiPo compatible charger for LiPos and LiFePO4 compatible charger for LiFePO4 batteries. They charge using a system called CC/CV charging. It stands for Constant Current / Constant Voltage. Basically, the charger will keep the current, or charge rate, constant until the battery reaches its peak voltage (4.2v/ 3,6V per cell in a battery pack). Then it will maintain that voltage, while reducing the current. On the other hand, NiMH and NiCd batteries charge best using a pulse charging method. Charging a LiPo / LiFePO4 battery in this way can have damaging effects, so it is important to use a LiPo / LiFePO4 compatible charger as appropriate.

Hmmm... a 4 cell LifePO4 @ 3.6V per cell is 14.2 Volts. My charger charges mine to 14.41 volts. Volts start out lower but increase to 14.41 as they reach a full charge. They said life expectancy of 5-7 years but that seems to be not to a discharge state we may be using them to which may effect them. But not lower than 2.8V per cell, which is 11.2V for a 4 cell.

Have about 180 cycles and the 10 amps are 3 years old.

See you in Perry.

Best. Tom.

[Roy Garden]

Lithium - anything batteries last best when not used to full discharge.
Going below 20% capacity in the battery, impacts the life of the battery
(same in your phone, constantly running it "Flat" does the internal battery

no favours at all.)

Chargers, it's not "Important" to use Proper chargers, it's "Vital".
Lead acid batteries are from the Steam era.
Modern Hi Capacity, Hi Discharge batteries are hugely powerful wee
beasties.
Not to be treated with the same practices as Lead Acid lumps.

Lithium Phosphate - LiFePo4 - Li4 batteries are less likely to misbehave
when charged badly.
LiPo - Lithium Ion, take badly to being dropped, shorted out, mischarged.
In use, liFePo4 batteries are slightly more idiot proof.
LiPo Batteries are lighter and have higher energy density.

You can Charge LiFePo4 in situ in the glider.
It is unwise to charge LiPo in the glider.

You _must_ have over discharge protection in place on a LiPo battery, it is

wise to have over dishcarge protection on a LiFePo4 battery.

[Roy Garden]

[SF]

Based on advice offered in this post, I left the old K2 batteries on float charge for several weeks to "equalize" the cells and attempt to revive their performance. (charged in parallel). I tested them yesterday with the two batteries in parallel powering a 2.3A load of side marker lights. I placed an amp meter on each battery capable of detecting reverse current (one battery charging the other battery) These batteries have very different discharge curves. At the start of the test, battery 2 was shouldering 1.7A of the load. At the end of the test battery 1 was shouldering 2.06A of the load. At no point in the test was there any reverse current or evidence of on battery charging the other battery. Leaving the battery on float did improve the combined Ah from 11.22 to 13.9Ah, better, but not back to acceptable for (2) 9 Ah batteries in parallel.

Conclusions:
-no observed problems with operating batteries in parallel on a common 12V bus, no evidence of one battery charging another found.
-These batteries have an observed life span of 5-6 years regardless of the advertised 2000 cycle lifespan.
-LiFePo4 batteries are still the way to go.
-Test your batteries at the beginning of each season to verify that there is sufficient capacity actually present to power your glider's load.

Disclaimer: This is based on a data set of 2. your individual results may vary significantly.

Enough of this, lets start flying again, instead of talking about flying.

SF

[jfitch]

Did you run only one discharge-recharge cycle? Some BMS cell balancing schemes seem to require a few deep discharge/full recharge cycles to properly equalize the cells.

If you decide to dispose of these batteries, I suggest cutting open the case and measuring the voltage on individual cells. This would tell us if cell balance, or basic loss of capacity is at fault. Always good to learn something.

[Steve Koerner]

SF: Yes, as Jon says, one cycle might not be enough. My batteries came back after successive long charge cycles with discharge in between as noted in my 2/29 post above. You may be tired of screwing with it, but you did get a substantial improvement with one long charge; it'd be interesting to see what a second or third would do.

It's a lousy state of affairs that these batteries can require such babying.

[SF]

I'm game, I'll repeat the charge discharge process a few times and report back.

SF

[dvmar...@gmail.com]

I have three K2 9.6 AH Lifepo4 batteries. I used a West Mountain Radio battery tester. Two of the batteries showed 8.7 and 8.5 AH for a full discharge (test cutoff at 10 volts) at 2.5 amp discharge rate. That seemed reasonable; however, the last battery showed 7 AH and that seemed low. These batteries are all two years old. I spoke with K2 Battery technical service and they suggested that the lower capacity battery could be improved by several complete discharge and recharge cycles. I did three complete discharge and recharge cycles on that battery and it improved to 8.83 AH. So it does appear that that strategy does indeed improve their capacity. I did the same exercise on the other two batteries and they improved slightly to 8.9 and 8.7.

David
ASG29E BV

[Charlie M. (UH & 002 owner/pilot)]

Sounds like this chemistry has a memory, sorta like NiCad and to a lesser extent NiMh. The LiFe does not have anywhere near as much the same issue it seems, but has it to a point.
I guess that means typically the batteries need to do a full discharge then charge a few times during a season just to keep it up.

Good info here though, thanks for posting.

[Dave Nadler]

On Sunday, February 19, 2017 at 3:22:29 PM UTC-5, Charlie M. (UH & 002 owner/pilot) wrote:
> Sounds like this chemistry has a memory...

No. This is about cell balancing.

[Charlie M. (UH & 002 owner/pilot)]

If they have a built in balance board, how is this balancing?

[jfitch]

On Sunday, February 19, 2017 at 3:28:49 PM UTC-8, Charlie M. (UH & 002 owner/pilot) wrote:
> If they have a built in balance board, how is this balancing?

The balancing mechanism depends on charge/discharge cycles to work. More $ophi$ticated balancing schemes balance even with no load/charge.

[glidergreg]

Richard just checked my 15 Amp and 12 Amp LifePo4 batteries purchased in 2013 from Bioenno, both are at 13.30 Volts waiting for the season to start. See you in Nephi

[Richard]

You have to check the fine print on their web page "battery allows for extraction of >90% of the rated capacity"

Richard

[uncl...@ix.netcom.com]

On Sunday, February 19, 2017 at 12:50:04 PM UTC-5, SF wrote:
> I'm game, I'll repeat the charge discharge process a few times and report back.
>
> SF

What cut off voltage are you using in your tests?
Also what discharge rate.
Thx
UH

[Richard]

With the West Mountain Radio CBA IV I use:

1 or 2 aH and 10 volts for the cutoff on the CBA IV. If you set the cutoff at 8 volts you will see if the battery BMS works.

You can use up to 100 watt about 6 aH with this device after that you go above 100 watts and need an amplifier.


Richard
www.craggyaero.com

[dvmar...@gmail.com]

I used 2.5 amp as the discharge rate, was about 45 watts, and used a cutoff of 10 volts. Also using a CBA IV.

David

[SF]

I was using 11.5 volts as the voltage to stop testing at. After 11.5 v not much left, and didn't want to over discharge for a test. Don't completely trust the bms board.

Sf

[Papa3]

Are LiFePo4 batteries not rated using a standard 1C discharge rate like SLA batteries? So, for a 10ah battery the rated capacity would be achieved at a discharge rate of 1a. 2.5a seems on the high side for a glider, even one with a fair number of electronic goodies. My ship draws not too much over 1a with FSG71, Trig, Clearnav, Flarm, and CNv. No?

P3

[uncl...@ix.netcom.com]

On Wednesday, February 22, 2017 at 10:20:46 PM UTC-5, Papa3 wrote:
> Are LiFePo4 batteries not rated using a standard 1C discharge rate like SLA batteries? So, for a 10ah battery the rated capacity would be achieved at a discharge rate of 1a. 2.5a seems on the high side for a glider, even one with a fair number of electronic goodies. My ship draws not too much over 1a with FSG71, Trig, Clearnav, Flarm, and CNv. No?
>
> P3

I'm testing at very close to 1 amp using six 2 ohm resistors that actually measure 13 ohms total and plan on using 12 volts as end point. I doesn't seem like there is much useful capacity past that point. I'll report my data back.
UH

[herbk...@gmail.com]

On Wednesday, February 22, 2017 at 9:20:46 PM UTC-6, Papa3 wrote:
> Are LiFePo4 batteries not rated using a standard 1C discharge rate like SLA batteries? So, for a 10ah battery the rated capacity would be achieved at a discharge rate of 1a. 2.5a seems on the high side for a glider, even one with a fair number of electronic goodies. My ship draws not too much over 1a with FSG71, Trig, Clearnav, Flarm, and CNv. No?
>
> P3

Eric, a 1C rating for charge and discharge would be 9 Amps for the batteries we are discussing. LiFePo4 will do that all day long but I doubt you would get 1,000+ cycles out of the battery. RC flight batteries are routinely sujected to 20-30C discharge rates (these are LiPo's) and they rarely make 100 cycles. They can also be aggressively charged at 3-4C. Wonder what that number would be for a Tesla battery on the quick charger. Compared to the older chemistries such as NiCd an NiMh, the new ones can sure take a beating.
Herb, J7

[Bruce Hoult]

Tesla's own "Supercharger" stations supply up to 120 kW (depending on the size of the car battery and it's existing charge state), and take 20 minutes to charge to 50%, 40 minutes to charge to 80%, and 75 minutes to 100%.

So the initial twenty minutes of charging is at an average of 1.5C and next 20 minutes at an average of 0.9C. So, not very extreme on the batteries.

Normal driving uses around 320 - 340 Wh/mi (200 - 210 Wh/km), so at 120 km/h a 75 kWh battery is being discharged at 0.32C, or a top end 100 kWh Tesla at 0.24C.

[Papa3]

What's a decimal among friends?

[Papa3]

[Bruce Hoult]

On Thursday, February 23, 2017 at 6:49:13 PM UTC+3, Papa3 wrote:
> What's a decimal among friends?

Do you have some issue with my calculations?

[kinsell]

He said 1C, meant to say .1C

I suppose battery mfgs use whatever discharge rating makes the numbers
look the best.

[Bruce Hoult]

Oh, referring to his own dodgy calculations earlier .. fair enough.

Generic Panasonic batteries last about 400 cycles of 1C charge/discharge before falling to 70% capacity. The actual ones built for Tesla are though to be good for up to 1000 cycles of that treatment. You can charge a Tesla at 1C, but you're not going to discharge it anywhere near that rate unless you're on a racetrack. With the actual typical owner's normal daily use of using maybe 10% - 20% of the battery capacity and keeping the charge between 50% and 80% they'll do the equivalent of maybe somewhere between 2000 and 5000 full cycles.

At 400 - 500 km range per full cycle, that's 800k to 2.5M km.

Should be enough for most owners.

Yes, if you do road trips every day and use the whole capacity every time and then fast charge them multiple times a day then you might only get 200k - 500k km out of a battery pack. You could even potentially kill a battery pack in a year. Even less if you use multiple drivers 24/7. If you're doing that I assume it's for a business venture, and you'd better just factor in $20k - $30k [1] each for new battery packs as part of your cost of doing business. If you call it 10c/km you're probably reasonably safe.

[1] Tesla have promised replacements 80 kWh packs for $12k, but only eight years after vehicle purchase. The cost to make them will drop a lot between now and then. Roadster owners have been charged $30k for an upgrade to a modern battery pack.

[kinsell]

And if they still don't look good enough, then they invent some
preposterous AH rating based on cranking amps, like some of the lithium
battery mfgs do.

[SF]

The tests I'm running at approx 2.5A are being run with two batteries in parallel. I'm still deep discharging and recharging the old K2's trying to bring them back to life. I'll report back when I'm finished.

[jave...@gmail.com]

Updating on my results from deep discharging/prolonged recharging.

My 2 season old K2 LiFePO4 battery was showing a drop to 60.5% (5.8 Ah)when tested using a West Mountain Radio CBA III with 1.5A constant discharge current and test cut off of 11.0V.

After 2 cycles of discharge and 10 day recharge, the battery is back to 93.2% (8.95 Ah) of original. Pretty good results.

[jfitch]

Keep in mind that it is the act of recharging that causes the cell balancing, once the battery is charged fully or near fully the cell balancing stops (in most of these cheap schemes). No cell balancing takes place (typically) on discharge as doing so wastes energy. The best strategy may be to do several discharge/charge cycles to 40 - 50% or so in succession. Slow charging may be best if you can arrange it - the bypass shunts are very limited in capacity and would be more effective with lower charging currents.

[Brian]

I recently consulted one of the K2 Battery representatives he told me the following...

I would suggest getting one of our chargers and charging the battery with it every few months to let the battery float and balance. It starts balancing at approximately 14.4V to 14.6V, and our charger is a 14.6V charger.

So it appears that balancing doesn't really start to occur until it reaches the 14.4 volts, and letting it float there for a while will help re-balance the cells.

Brian

[uncl...@ix.netcom.com]

Update after testing four batteries. All charged and allowed to balance over night
#1- K2: run 1 was 6AH, run 2 was 6AH
#2- K2: run 1 was 7.75 AH, run 2 was 8.33AH
#3- K2: run 1 was 6.50 AH, run 2 was 8.75 AH
#4- Stark: run 1 was 7.2 AH, run 2 was 8.50

I'm going to do another cycle to see if any improve.
FWIW
UH

[Roy Garden]

>> > Are LiFePo4 batteries not rated using a standard 1C discharge rate

>like=

> SLA batteries? So, for a 10ah battery the rated capacity would be

>achieve=

>d at a discharge rate of 1a. 2.5a seems on the high side for a glider,

>ev=

>en one with a fair number of electronic goodies. My ship draws not too

>mu=
>ch over 1a with FSG71, Trig, Clearnav, Flarm, and CNv. No? =20

On the last glider, I was blowing 3A fuses when running the aux refuelling

pump (when the rest of the avionics were on)
Uprated the fuses on both main batteries to 5A.
Ended up carrying 58AH @ 12V
2 x 22AH LiPo (Avionics)
1 x 14AH LifePo4 (Engine start duties, in flight charged from engine)
Would last all day at very low temps.

We really need to stop faffing about with batteries invented 2 centuries
ago to try to run modern avionics.

LiPo's are not idiot friendly batteries (despite being in almost every
mobile
phone on the planet) LiFePo4 are slightly more Luddite-friendly.
But when you change battery chemistry, you need to change battery
chargers.
You don't run a Diesel engine on Gas.
You don't charge a LiPo from a lead acid charger.

[Jim White]

At 10:29 01 March 2017, Roy Garden wrote:
>You don't charge a LiPo from a lead acid charger.
>

>Not strictly true Roy. According to the datasheet and user manual A123
batteries are compatible with a standard SLA charger however will probably
be optimum with a proper one. I use a Ctek Lithium XS for mine.

[Roy Garden]

At 11:58 01 March 2017, Jim White wrote:
>At 10:29 01 March 2017, Roy Garden wrote:
>>You don't charge a LiPo from a lead acid charger.
>>
>>Not strictly true Roy. According to the datasheet and user manual A12

>batteries are compatible with a standard SLA charger however will
probabl

>be optimum with a proper one. I use a Ctek Lithium XS for mine.
>

Absolutely, strictly, true.
You'll "Get away" with occasional charges from a lead acid battery charger

on LiFePo4 batteries (If the voltage is vaguely compatible)
But on a pack, you'll loose the "Balance" in the pack and in fairly short
order destroy the pack.

The differences between PB, LiPo and LiFePo4 are of the order of putting
Petrol into a diesel engine.
If you put the wrong stuff in the wrong place, You'll break things.

PB Chargers do not have such robust dead short protection as modern
chargers, and with LiPo can leave you open to causing a thermal runaway
on a LiPo.

Get modern chargers and batteries.

[jfitch]

I'll agree with the sentiment to use Li chargers with Li batteries, however the comparison to petrol in a diesel engine is a bit far fetched. The LiFePo4 batteries that we should be using in gliders all have an on board BMS that balances the cells and prevents over and under charging. Any LA charger is current limited by design, even very old fero resonant versions. LiFePo4 batteries have to be heated to something like 600C to achieve anything like thermal runaway. On the other hand LiPo batteries are relatively easy to drive into thermal runaway, and that is the reason they should not be used in a glider.

Undercharging LFPs does shorten life expectancy, and most LA chargers are limited to 14V or so, which is likely to undercharge an LFP.

[JS]

On Wednesday, March 1, 2017 at 2:30:05 AM UTC-8, Roy Garden wrote:
> (schnipp)

> We really need to stop faffing about with batteries invented 2 centuries
> ago to try to run modern avionics.
>

Agree the old SLA stuff is rubbish.
You can as stated "get away with" charging "SLA replacement" LiFePO4 packs on almost anything, including a direct connection to your car's cigarette lighter.
But not a good way to preserve the life of the battery.
Thanks to all posting comments and results on multiple deep discharge! I'll give it a go when the weather is nice enough to pull the fuselage out.
Jim

[Jim White]

At 13:29 01 March 2017, Roy Garden wrote:
>At 11:58 01 March 2017, Jim White wrote:
>>At 10:29 01 March 2017, Roy Garden wrote:
>>>You don't charge a LiPo from a lead acid charger.
>>>
>>>Not strictly true Roy. According to the datasheet and user manual A12
>>batteries are compatible with a standard SLA charger however will
>probabl
>>be optimum with a proper one. I use a Ctek Lithium XS for mine.
>>
>Absolutely, strictly, true.
>You'll "Get away" with occasional charges from a lead acid battery charge
>

>on LiFePo4 batteries (If the voltage is vaguely compatible)
>But on a pack, you'll loose the "Balance" in the pack and in fairly short

>order destroy the pack.
>
>The differences between PB, LiPo and LiFePo4 are of the order of putting
>Petrol into a diesel engine.
>If you put the wrong stuff in the wrong place, You'll break things.
>
>PB Chargers do not have such robust dead short protection as modern
>chargers, and with LiPo can leave you open to causing a thermal runaway
>on a LiPo.
>
>Get modern chargers and batteries.
>
>

Roy, I suggest you actually read the literature about the battery to which
I refer before you diss my post. A123 batteries are perfectly happy with an
SLA charger as the BMS is rather good by comparison with cheaper types.

And as for petrol vs diesel engines you should perhaps read up on tank
design too

[kevi...@gmail.com]

> So it appears that balancing doesn't really start to occur until it reaches the 14.4 volts, and letting it float there for a while will help re-balance the cells.
>
> Brian

Did they give you any idea how long to let it float? Overnight, a few days, a week?

Kevin
92

[uncl...@ix.netcom.com]

I did a 3rd cycle on one battery with 3 day float and got exactly the same results as 2nd cycle with 1 day float. This on a very good battery.
FWIW
UH

[Brian]

Nope I posted exactly what he told me.

Brian

[Jim White]

Has anyone built a suitable 12V Coulomb counter yet?

[clewi...@gmail.com]

Thank you for the West Mountain Radio battery tester recommendation Richard. It's a cracker of a little unit.

Casey

[SF]

My oldest K2 battery (6 years old), has obviously lost one or more cells. During an unloaded voltage check it appears to be fine. Put a load on it, and the voltages plummets to a little over 12V, then starts a gradual decline. With about 2AH left out of 9AH, only available at a voltage lower than desired, it's going to the recycler.

The newer (5 year old) K2 responded pretty well to the discharge - charge - leave it on float for a few days - repeat process. it came back to about 80% of it's original capacity while discharging down to 11.5V.

The take away from this is if you think you may have a LiFePo4 battery issue, a test under load, after a few times through the discharge - charge - leave it on float for a few days - repeat process. will confirm it or fix it. The old myth that one battery will charge the other battery if you run them in parallel has also been successfully debunked. So go ahead put both batteries on the 12V bus, and you have one less switch to flip in flight,.

SF

We may have set a new record with this topic for actually staying on track. Don't know who is keeping up with this, someone somewhere probably has a graph or two to document what the average number of posts it takes to start arguing about the rules or Flarm stealth mode on a post about a canopy cover.

[uncl...@ix.netcom.com]

Make batteries great again!
LOL
UH

[raxy...@gmail.com]

Its a useful discussion, if only to show the confusion about the LiFePO4 batteries. I've just got a Bienno 20AH battery to replace my old 20AH lead-acid battery (that really didn't give me a useful 20AH, as neither did the same lead-acid battery before that). 20AH is a large size for a glider, but I need a heavy nose battery for my motorglider anyway. The Bienno is a featherweight compared to the lead-acid, so I may need to add some weight in the nose now. I decided on a 20AH capacity because 1) it was the exact same size as my old lead-acid 20AH battery, so the battery holder didn't need to be altered 2) I distrust the manufacturer's claims of capacity, so only expect to get maybe 15AH 3) my impression (data is hard to find) is that battery lifetime (number of charge-discharge cycles) gets much shorter if a battery is routinely discharged more than 50%. So I'm planning on using 50% discharge (7.5AH) on my flights. Although the 20AH size is more expensive, I hope the lower % discharge will give me a compensating increase in battery lifetime. At my draw of 1.8A, 7.5AH is a 4hr flight. So I should typically land with the battery still strong.

[cliff...@gmail.com]

So after all this, the question remains, are they worth it? I'm ready to replace my 14volt lead acids, the advantage is that the Lifepo4 will give me enough voltage with out building 14volt packs of lead acid. So again are they worth the extra hassle/money?

[herbk...@gmail.com]

On Tuesday, March 7, 2017 at 6:26:07 PM UTC-6, cliff...@gmail.com wrote:
> So after all this, the question remains, are they worth it? I'm ready to replace my 14volt lead acids, the advantage is that the Lifepo4 will give me enough voltage with out building 14volt packs of lead acid. So again are they worth the extra hassle/money?

The answer is clear as can be Cliff: No hassle and well worth the money. Take the plunge.. Lead-acid is so quaint.. keep up with the Jones'es.

[Eric Greenwell]

raxy...@gmail.com wrote on 3/7/2017 4:25 PM:
> 3) my impression (data is hard to find) is that battery lifetime (number of charge-discharge cycles) gets much shorter if a battery is routinely discharged more than 50%

LiFe batteries "lifetime" is generally not affected by discharges as low as 80%.
The 50% number you mention is just a rule-of-thumb for deep cycle lead acid
batteries, and lead acid "lifetime" is substantially reduced if it's routinely
discharged to 80%.

--
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
- "Transponders in Sailplanes - Dec 2014a" also ADS-B, PCAS, Flarm

http://soaringsafety.org/prevention/Guide-to-transponders-in-sailplanes-2014A.pdf

[SF]

Yes worth it. Higher voltage will be appreciated by the radio. More capacity.
Lighter weight, longer life.
Not really a hassle with the right charger, just a little different.

[Eric Greenwell]

SF wrote on 3/9/2017 6:16 PM:
> Yes worth it. Higher voltage will be appreciated by the radio.

The radio will show it's appreciation by using less current; otherwise, a "modern"
radio won't care. "Modern" radios use power regulators that provide the correct
wattage to the radio, within a wide range of input voltages.

[SF]

My Dittle FSG60M, (May it RIP after it's death three weeks ago) Was the first thing in the airplane that suffered from the effects of low voltage. It seemed to receive just fine, but it made me sound like a Wookie when trying to transmit. That is the source material for my radio comment.

I've hated sailplane batteries ever since one died on a gold distance badge flight, I was 10 miles out at 6,000 FT. My argument that the landing witness should suffice for the missing final 10 miles of the .igc file, wasn't persuasive enough, so I had to do it again, with a different battery.

[jfitch]

The thread has inspired me to test my LFPs.

3 year old Starkpower 12AH used for instruments, 11.86AH (tested to 11V @ 1.5A). This improved to 11.91 on the second cycle.

3 year old Starkpower 9AH used for self rig wing dolly, 8.60AH (to 11V @ 1A).

2 year old CTC 19.8AH used for engine start, 19.38AH (to 11V @ 2A). I may give this one a second cycle to see if it improves.

While I was at it, a 5 year old PowerSonic 14 AH SLA, 9.8AH (11V @ 1A). This battery had been sitting idle and uncharged for 3 years, till I charged it for the test.

The SLA had a nearly linear drop from 12.8V to 11V, dropping under 12V at about 60% discharge, while all of the LFPs stayed above 12.5 until about the 90% discharged point.

[Vaughn Simon]

On 3/12/2017 10:54 PM, jfitch wrote:
> While I was at it, a 5 year old PowerSonic 14 AH SLA, 9.8AH (11V @ 1A). This battery had been sitting idle and uncharged for 3 years, till I charged it for the test.

I would have expected 3 years of uncharged storage to turn that
Powersonic into a doorstop.

[jfitch]

Yeah, I was kind of surprised it still had useable capacity.

[Eric Greenwell]

SF wrote on 3/12/2017 5:15 PM:
> My Dittle FSG60M, (May it RIP after it's death three weeks ago) Was the first thing in the airplane that suffered from the effects of low voltage.

Definitely not a "modern radio", as the design is over 37 years old, but it was a
very good radio back then.

[cliff...@gmail.com]

Mine is a Terra 720 and suffers badly during transmit when voltage drops below 12v so I have always made 14v packs which are over 3+ years old now and need replacing. Hence the quandary about new Lifepo4's I am in communication with "Dakota" batteries and they are putting a BMS system into there batteries the has cell balancing starting in April sometime. And are selling for about $90 ea for 10 amp hour.

[George Haeh]

I've had my K2's for about five years now. Last spring I bought a CTEK LiFePo4 charger, which has 8 stages and ran the batteries through several recharges. Each time the batteries seemed to absorb a bit more.

Last week I flew one battery for over 7 hours on two flights. The Air Glide S showed the voltage flipping between 11.9 & 12.1. Note that the Air Glide S seems to underread by about 0.6V compared to the Tasman. Poking around with probes showed no drop in voltage between the battery and the Air Glide.

Back on the charger it took over three hours to get the battery back up to float. The charger was quite warm for the 2.5 hours in stage 2.

The other battery flown for three hours charged back up in a little over an hour.

I suspect that the batteries need heavier usage than just 3-4 hours of flight before accepting a full recharge.

[kinsell]

You've got two old batteries, with two different state of charges.
Rather than speculating on some memory effect, it might be more likely
that the batteries are no longer equivalent, perhaps one has a few weak
cells and needs a bunch of balancing.

That was an interesting thread you bumped, didn't realize just how much
misinformation got crammed into that one. Someone stated that you don't
charge a LI-PO battery with a SLA charger, certainly a true statement.
Multiple people responded by saying that it's fine to charge an LFP with
a SLA charger. It's almost as if they don't know the difference. With
all the discussion about how typical BMS boards need high voltage
applied for a long period of time in order to balance cells, some people
still think the SLA charger works fine for LFP. I guess it's fine as
long as you don't care about the lifetime of your battery, and if you
don't care about getting a full charge.

Then there was another discussion about how radios supposedly last
longer with higher voltage, because someone's 37 year old radio just
died. I really don't think it would have lasted any longer no matter
what voltage was used. Similarly, radios that we use don't draw less
current with higher voltage, the only instrument in your panel that
might draw a bit less current is a transponder.

-Dave

[2G]

"the only instrument in your panel that
might draw a bit less current is a transponder"

I seriously doubt it. All modern avionics are designed to operate over a wide input voltage range; they have internal dc-dc conversion circuits that transform the supply voltage to a regulated, operating voltage. Trig, for instance, specifies an input voltage of 11 to 33 V.

Tom

[krasw]

I installed a small coulometer (with LCD-display, available from Ebay) between my charger and battery. I can also discharge battery (with car tail light bulb as load) with coulometer. For example, before disconnecting charger I can see that charger put 3 Ah to battery. Annual test shows total capacity from 100% charge to 0%. No more guesswork about battery condition.

There would be market for full-blown panel mounted battery monitor system for gliders. One that monitors each battery charge and discharge, with built in breakers etc.

[Martin Gregorie]

On Wed, 08 Aug 2018 23:55:38 -0700, krasw wrote:

> I installed a small coulometer (with LCD-display, available from Ebay)
> between my charger and battery.
>

Multi-chemistry chargers are sold for RC model flying that are also
suitable for checking capacity on our batteries and can handle any
chemistry that is normally used in gliders. Prices vary (of course)
depending on capabilities, but are generally reasonable unless you want
the sort of gorilla charger used by the F5x crowd. In the USA HobbyKing
would a a reasonable place to start looking.

But, none of them will fit in a glider's panel.



--
Martin | martin at
Gregorie | gregorie dot org