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Test results LiFePO4 glider batteries after 6 years



 
 
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  #11  
Old January 29th 17, 11:27 PM posted to rec.aviation.soaring
SF
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Default Test results LiFePO4 glider batteries after 6 years

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
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  #12  
Old January 29th 17, 11:31 PM posted to rec.aviation.soaring
SF
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Default Test results LiFePO4 glider batteries after 6 years

On Sunday, January 29, 2017 at 5:05:25 PM UTC-5, Steve Koerner wrote:
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.


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

Scott
  #13  
Old January 30th 17, 12:22 AM posted to rec.aviation.soaring
jfitch
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Default Test results LiFePO4 glider batteries after 6 years

On Sunday, January 29, 2017 at 2:05:25 PM UTC-8, Steve Koerner wrote:
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.


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.
  #14  
Old January 30th 17, 02:31 AM posted to rec.aviation.soaring
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Default Test results LiFePO4 glider batteries after 6 years

How I test my batteries

Thanks Scott
  #15  
Old January 30th 17, 02:52 AM posted to rec.aviation.soaring
Richard[_9_]
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Default Test results LiFePO4 glider batteries after 6 years

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
  #16  
Old January 30th 17, 04:26 AM posted to rec.aviation.soaring
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Default 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


  #17  
Old January 30th 17, 02:32 PM posted to rec.aviation.soaring
Charlie M. (UH & 002 owner/pilot)
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Default Test results LiFePO4 glider batteries after 6 years

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.
  #18  
Old January 31st 17, 12:29 AM posted to rec.aviation.soaring
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Default Test results LiFePO4 glider batteries after 6 years

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
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  #19  
Old January 31st 17, 01:23 AM posted to rec.aviation.soaring
SF
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Default Test results LiFePO4 glider batteries after 6 years

I was using a charger from K2
  #20  
Old January 31st 17, 03:48 AM posted to rec.aviation.soaring
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Default Test results LiFePO4 glider batteries after 6 years

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




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