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Test results LiFePO4 glider batteries after 6 years



 
 
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  #21  
Old January 31st 17, 08:12 PM posted to rec.aviation.soaring
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Default Test results LiFePO4 glider batteries after 6 years

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
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  #22  
Old January 31st 17, 08:28 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

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.
  #23  
Old January 31st 17, 09:59 PM posted to rec.aviation.soaring
SF
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Default Test results LiFePO4 glider batteries after 6 years

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
  #24  
Old January 31st 17, 10:36 PM posted to rec.aviation.soaring
Matt Herron Jr.
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Default Test results LiFePO4 glider batteries after 6 years

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
..
  #25  
Old February 1st 17, 06:30 AM posted to rec.aviation.soaring
bumper[_4_]
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Default Test results LiFePO4 glider batteries after 6 years

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
  #26  
Old February 1st 17, 02:02 PM posted to rec.aviation.soaring
glidergreg
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Default Test results LiFePO4 glider batteries after 6 years

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.

SF


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/collect...d-green-case-1
  #27  
Old February 1st 17, 10:36 PM posted to rec.aviation.soaring
Richard[_9_]
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Default Test results LiFePO4 glider batteries after 6 years

On Wednesday, February 1, 2017 at 6:02:48 AM UTC-8, glidergreg wrote:
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.

SF


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/collect...d-green-case-1


Greg,

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

Richard.
  #28  
Old February 2nd 17, 01:20 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 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 *******s) 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.
  #29  
Old February 2nd 17, 01:43 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 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
  #30  
Old February 7th 17, 01:30 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 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
 




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