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Test results LiFePO4 glider batteries after 6 years



 
 
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  #71  
Old March 1st 17, 11:29 AM posted to rec.aviation.soaring
Roy Garden
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Posts: 17
Default Test results LiFePO4 glider batteries after 6 years


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.

  #72  
Old March 1st 17, 12:58 PM posted to rec.aviation.soaring
Jim White[_3_]
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Posts: 286
Default Test results LiFePO4 glider batteries after 6 years

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.

  #73  
Old March 1st 17, 02:29 PM posted to rec.aviation.soaring
Roy Garden
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Posts: 17
Default Test results LiFePO4 glider batteries after 6 years

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.

  #74  
Old March 1st 17, 04:07 PM posted to rec.aviation.soaring
jfitch
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Posts: 1,134
Default Test results LiFePO4 glider batteries after 6 years

On Wednesday, March 1, 2017 at 5:30:06 AM UTC-8, 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 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.


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.
  #75  
Old March 1st 17, 05:50 PM posted to rec.aviation.soaring
JS
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Posts: 1,384
Default Test results LiFePO4 glider batteries after 6 years

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
  #76  
Old March 1st 17, 07:09 PM posted to rec.aviation.soaring
Jim White[_3_]
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Posts: 286
Default Test results LiFePO4 glider batteries after 6 years

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

  #77  
Old March 4th 17, 04:18 PM posted to rec.aviation.soaring
[email protected]
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Posts: 160
Default Test results LiFePO4 glider batteries after 6 years


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
  #78  
Old March 4th 17, 04:54 PM posted to rec.aviation.soaring
[email protected]
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Posts: 2,124
Default Test results LiFePO4 glider batteries after 6 years

On Saturday, March 4, 2017 at 10:18:26 AM UTC-5, wrote:
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


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
  #79  
Old March 6th 17, 05:37 AM posted to rec.aviation.soaring
Brian[_1_]
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Posts: 399
Default Test results LiFePO4 glider batteries after 6 years

Nope I posted exactly what he told me.

Brian
  #80  
Old March 6th 17, 06:48 PM posted to rec.aviation.soaring
Jim White[_3_]
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Posts: 286
Default Test results LiFePO4 glider batteries after 6 years

Has anyone built a suitable 12V Coulomb counter yet?

 




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