Test results LiFePO4 glider batteries after 6 years

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.


On Sunday, January 29, 2017 at 6:52:44 PM UTC-8, Richard wrote:
On Sunday, January 29, 2017 at 6:31:39 PM UTC-8, 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

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.

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

I was using a charger from K2

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

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

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

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.

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

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
..

The CTC batteries I bought from:

http://www.batterypete.com/batteries...ery-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