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Test results LiFePO4 glider batteries after 6 years



 
 
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  #1  
Old January 29th 17, 07:41 PM posted to rec.aviation.soaring
SF
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Default Test results LiFePO4 glider batteries after 6 years

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

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  #2  
Old January 29th 17, 07:55 PM posted to rec.aviation.soaring
John Carlyle
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Posts: 322
Default Test results LiFePO4 glider batteries after 6 years

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

-John, Q3

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.

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

  #3  
Old January 29th 17, 08:20 PM posted to rec.aviation.soaring
SF
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Posts: 194
Default Test results LiFePO4 glider batteries after 6 years

My battery cabinet is in my home office. 65-80F, Depending on Spousal override.
  #4  
Old January 29th 17, 09:14 PM posted to rec.aviation.soaring
[email protected]
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Default Test results LiFePO4 glider batteries after 6 years

Hi SF,

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

CJ
  #5  
Old January 29th 17, 09:37 PM posted to rec.aviation.soaring
John Carlyle
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Default Test results LiFePO4 glider batteries after 6 years

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
  #6  
Old January 29th 17, 09:42 PM posted to rec.aviation.soaring
Tango Eight
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Default Test results LiFePO4 glider batteries after 6 years

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
  #7  
Old January 29th 17, 09:50 PM posted to rec.aviation.soaring
John Carlyle
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Posts: 322
Default Test results LiFePO4 glider batteries after 6 years

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
  #8  
Old January 29th 17, 10:05 PM posted to rec.aviation.soaring
Steve Koerner
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Default Test results LiFePO4 glider batteries after 6 years

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.
  #9  
Old January 29th 17, 10:05 PM posted to rec.aviation.soaring
Tango Eight
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Default Test results LiFePO4 glider batteries after 6 years

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
  #10  
Old January 29th 17, 10:52 PM posted to rec.aviation.soaring
John Carlyle
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Posts: 322
Default Test results LiFePO4 glider batteries after 6 years

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

-John, Q3

On Sunday, January 29, 2017 at 5:06:00 PM UTC-5, Tango Eight wrote:
Call it 150 cycles to 1/2 charge on average.

T8


 




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