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A Simple Question About LiFePO4 Batteries



 
 
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  #41  
Old May 18th 18, 05:27 PM posted to rec.aviation.soaring
Charlie M. (UH & 002 owner/pilot)
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Default A Simple Question About LiFePO4 Batteries

No, pulling power from any battery is a chemical reaction. Most reactions work better the warmer they are (to a point).
When I do discharge testing on large UPS batteries, the assumption is 77*F, there are charts to offset the rate/runtime based on battery temp.
Low temps give less amperage and shorter run times.

Part of why an old car battery has issues when it gets cold.
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  #42  
Old May 18th 18, 06:16 PM posted to rec.aviation.soaring
Tom Kelley #711
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Posts: 271
Default A Simple Question About LiFePO4 Batteries

On Friday, May 11, 2018 at 1:37:03 PM UTC-6, wrote:
Not to start another chapter in "Battery Wars" but I have a simple question about "drop in" LiFePO4 battery replacements for SLA batteries in gliders.

For years, I've used an SLA battery with the same footprint as the common glider size of 7Ah to 9Ah--i.e., 5.95" x 2.56"--except a little taller--i.e., 4.61" high vs. 3.86" (specs are from the PowerSonic line but other brands are similar). It's an easy swap in my ASW 24, only requiring a different hold-down strap. There's about 20% more internal volume, which seems to equate to at least 20% more claimed capacity. I've used enough of these that I know they do perform longer than the conventional-size SLA batteries most pilots use.

However, I can't find a LiFePO4 equivalent for it. Does such a thing exist? All I've seen discussed here or available online seem to be the "traditional" size. I've been told that this is because there's already excess space inside the enclosure, that it's not packed to the gills with mat/chemicals as SLAs are, and that the extra 3/4" wouldn't allow adding additional cells. And besides, I don't need it anyway (I'm running PowerFLARM, radio, CNv vario, and PNA; no transponder yet).

Then I see that some LiFePO4 batteries are rated slightly higher for the same enclosure size. Even the K2 battery touted in adverts as "10 Ah" seems to be 9.6 Ah in the specs. And that's ignoring loads, discharge rates, temperatures, etc.

Given the price differential and the necessity for a new charger (although not according to the K2 site), and especially in light of the recent stories of LiFePO4 batteries crapping out long before their promised lifespans, maybe I should just continue to buy a new SLA battery every year or two and wait for this fad to pass.

As I said, a simple question.

Chip Bearden


I use these on my 29(sorry Richard), slides right in and my battery compartments are the same size as a 27.

https://www.bioennopower.com/collect...d-green-case-1

Not sure about your 24 size battery compartment. When measured are 5.95Lx2..96Wx3.66H. Last flight went over 6 hrs on one. My 10 amps are the same size and what I was using, I use about 1.32 amps per hour as I don't use the radio very much. Do have a Sandia transponder. When recharged it showed it had used 6.929 amps.
Used SLA's, now after using these would not go back. Have had no problems with them and 2 are now going on more than several years old and have well over 200 recharge cycles on them. I recharge them with my RC charger which I can set the charge rate. Been recharging them at 5 amps since new.

Ya, it's kinda late to your post, but may help someone else.

Best. Tom #711.
  #43  
Old May 18th 18, 06:56 PM posted to rec.aviation.soaring
Richard Pfiffner[_2_]
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Posts: 99
Default A Simple Question About LiFePO4 Batteries

On Friday, May 18, 2018 at 10:16:07 AM UTC-7, Tom Kelley #711 wrote:
On Friday, May 11, 2018 at 1:37:03 PM UTC-6, wrote:
Not to start another chapter in "Battery Wars" but I have a simple question about "drop in" LiFePO4 battery replacements for SLA batteries in gliders.

For years, I've used an SLA battery with the same footprint as the common glider size of 7Ah to 9Ah--i.e., 5.95" x 2.56"--except a little taller--i.e., 4.61" high vs. 3.86" (specs are from the PowerSonic line but other brands are similar). It's an easy swap in my ASW 24, only requiring a different hold-down strap. There's about 20% more internal volume, which seems to equate to at least 20% more claimed capacity. I've used enough of these that I know they do perform longer than the conventional-size SLA batteries most pilots use.

However, I can't find a LiFePO4 equivalent for it. Does such a thing exist? All I've seen discussed here or available online seem to be the "traditional" size. I've been told that this is because there's already excess space inside the enclosure, that it's not packed to the gills with mat/chemicals as SLAs are, and that the extra 3/4" wouldn't allow adding additional cells. And besides, I don't need it anyway (I'm running PowerFLARM, radio, CNv vario, and PNA; no transponder yet).

Then I see that some LiFePO4 batteries are rated slightly higher for the same enclosure size. Even the K2 battery touted in adverts as "10 Ah" seems to be 9.6 Ah in the specs. And that's ignoring loads, discharge rates, temperatures, etc.

Given the price differential and the necessity for a new charger (although not according to the K2 site), and especially in light of the recent stories of LiFePO4 batteries crapping out long before their promised lifespans, maybe I should just continue to buy a new SLA battery every year or two and wait for this fad to pass.

As I said, a simple question.

Chip Bearden


I use these on my 29(sorry Richard), slides right in and my battery compartments are the same size as a 27.

https://www.bioennopower.com/collect...d-green-case-1

Not sure about your 24 size battery compartment. When measured are 5.95Lx2.96Wx3.66H. Last flight went over 6 hrs on one. My 10 amps are the same size and what I was using, I use about 1.32 amps per hour as I don't use the radio very much. Do have a Sandia transponder. When recharged it showed it had used 6.929 amps.
Used SLA's, now after using these would not go back. Have had no problems with them and 2 are now going on more than several years old and have well over 200 recharge cycles on them. I recharge them with my RC charger which I can set the charge rate. Been recharging them at 5 amps since new.

Ya, it's kinda late to your post, but may help someone else.

Best. Tom #711.


Tom,

I used to sell Bioenno until I got an entire bad batch of Batteries.

Less than 5 AH for a 9Ah Battery.

Richard
www.craggyaero.com
  #44  
Old May 18th 18, 07:01 PM posted to rec.aviation.soaring
Richard Pfiffner[_2_]
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Posts: 99
Default A Simple Question About LiFePO4 Batteries

On Friday, May 18, 2018 at 10:16:07 AM UTC-7, Tom Kelley #711 wrote:
On Friday, May 11, 2018 at 1:37:03 PM UTC-6, wrote:
Not to start another chapter in "Battery Wars" but I have a simple question about "drop in" LiFePO4 battery replacements for SLA batteries in gliders.

For years, I've used an SLA battery with the same footprint as the common glider size of 7Ah to 9Ah--i.e., 5.95" x 2.56"--except a little taller--i.e., 4.61" high vs. 3.86" (specs are from the PowerSonic line but other brands are similar). It's an easy swap in my ASW 24, only requiring a different hold-down strap. There's about 20% more internal volume, which seems to equate to at least 20% more claimed capacity. I've used enough of these that I know they do perform longer than the conventional-size SLA batteries most pilots use.

However, I can't find a LiFePO4 equivalent for it. Does such a thing exist? All I've seen discussed here or available online seem to be the "traditional" size. I've been told that this is because there's already excess space inside the enclosure, that it's not packed to the gills with mat/chemicals as SLAs are, and that the extra 3/4" wouldn't allow adding additional cells. And besides, I don't need it anyway (I'm running PowerFLARM, radio, CNv vario, and PNA; no transponder yet).

Then I see that some LiFePO4 batteries are rated slightly higher for the same enclosure size. Even the K2 battery touted in adverts as "10 Ah" seems to be 9.6 Ah in the specs. And that's ignoring loads, discharge rates, temperatures, etc.

Given the price differential and the necessity for a new charger (although not according to the K2 site), and especially in light of the recent stories of LiFePO4 batteries crapping out long before their promised lifespans, maybe I should just continue to buy a new SLA battery every year or two and wait for this fad to pass.

As I said, a simple question.

Chip Bearden


I use these on my 29(sorry Richard), slides right in and my battery compartments are the same size as a 27.

https://www.bioennopower.com/collect...d-green-case-1

Not sure about your 24 size battery compartment. When measured are 5.95Lx2.96Wx3.66H. Last flight went over 6 hrs on one. My 10 amps are the same size and what I was using, I use about 1.32 amps per hour as I don't use the radio very much. Do have a Sandia transponder. When recharged it showed it had used 6.929 amps.
Used SLA's, now after using these would not go back. Have had no problems with them and 2 are now going on more than several years old and have well over 200 recharge cycles on them. I recharge them with my RC charger which I can set the charge rate. Been recharging them at 5 amps since new.

Ya, it's kinda late to your post, but may help someone else.

Best. Tom #711.


I used to sell Bioe until I got a bad batch 5AH for a 9 AH battery. They replaced but it took awhile.

Richard
  #45  
Old May 18th 18, 09:58 PM posted to rec.aviation.soaring
[email protected]
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Posts: 443
Default A Simple Question About LiFePO4 Batteries

On Friday, May 18, 2018 at 8:24:11 AM UTC-4, wrote:
However, I can't find a LiFePO4 equivalent for it. Does such a thing exist?


How about this one?

https://www.batteryspace.com/lifepo4...assed-dgr.aspx


YES, that's the size!!! Don't know what I couldn't find this anywhere. Don't recognize the brand name but that's not necessarily an impediment. Anyone have experience with Powerizer, specifically their LiFePO4 batteries?

Chip Bearden
  #46  
Old May 19th 18, 02:34 AM posted to rec.aviation.soaring
[email protected]
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Default A Simple Question About LiFePO4 Batteries

How about this one?

https://www.batteryspace.com/lifepo4...ssed-dgr..aspx

I've been using these for 2 years now, and I am generally satisfied, having nothing else but Powersonic 12v 15 Mah SLA to compare, but I am still getting power above 12.8 volts after 5 hours running radio, S80, PowerFlarm and an old Becker 5401/3401 Mode C 250 Watt transponder.

Using the recommended charger overnight, I start the flight at 13.4 volts and after several hours at high altitude and OAT at 30 degrees F, I am still getting enough to keep everything happy. No complaints, except the built-in LED
pushbutton display is not visible unless I untape the inspection hatch and deal with the contortions needed to see the three power level indicators. No big deal, as there are voltage indicators on the S80, the Becker 4201 radio and my new Trig TT22 transponder. As well as a dedicated LCD voltage display (https://www.lascarelectronics.com/la...ment-emv-1125/)
  #47  
Old May 19th 18, 01:38 PM posted to rec.aviation.soaring
Tango Eight
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Posts: 615
Default A Simple Question About LiFePO4 Batteries

On Friday, May 18, 2018 at 11:05:47 AM UTC-4, wrote:
Interesting - the discharge voltage goes down with lower temperatures - isn't that the opposite of lead-acid? At the least, lead-acid needs higher CHARGING voltages when it's cold.

How well does a microAir radio, which is finicky at low SLA voltages, do with a "12V" LFP battery, which offers a slightly higher voltage on the discharge curve?


Those voltage curves apply to 0.5C discharge, i.e. a two hour discharge rate. The primary reason for the change in behavior at low temperature is increasing internal resistance, not decreasing open circuit voltage. Compare to similar curves for SLA batteries, if you can find them (they'll probably be at slower discharge rates).

Under real world glider use, LFP batteries perform better than SLA batteries in cold conditions. But don't recharge below 0 C.

T8
  #48  
Old May 20th 18, 02:58 AM posted to rec.aviation.soaring
[email protected]
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Default A Simple Question About LiFePO4 Batteries

My Xcom radio contunually shows “low bat” wth Lithium battery until about 8 hours when it becomes normal.
I suspect the high voltage triggers the “low bat” signal.
  #50  
Old May 25th 18, 04:27 PM posted to rec.aviation.soaring
[email protected]
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Posts: 211
Default A Simple Question About LiFePO4 Batteries

On Saturday, May 19, 2018 at 8:38:15 AM UTC-4, Tango Eight wrote:
On Friday, May 18, 2018 at 11:05:47 AM UTC-4, wrote:
Interesting - the discharge voltage goes down with lower temperatures - isn't that the opposite of lead-acid? At the least, lead-acid needs higher CHARGING voltages when it's cold.

How well does a microAir radio, which is finicky at low SLA voltages, do with a "12V" LFP battery, which offers a slightly higher voltage on the discharge curve?


Those voltage curves apply to 0.5C discharge, i.e. a two hour discharge rate. The primary reason for the change in behavior at low temperature is increasing internal resistance, not decreasing open circuit voltage. Compare to similar curves for SLA batteries, if you can find them (they'll probably be at slower discharge rates).

Under real world glider use, LFP batteries perform better than SLA batteries in cold conditions. But don't recharge below 0 C.

T8


The claims that one should not charge LiFePO4 batteries below 0 deg C - but charge as fast as you want at +1 C - don't make sense. I've read that there are issues at low temperatures with the lithium plating the graphite anode (or is it the cathode?) instead of being absorbed into it, due to slower reactions. OK, but then the charging rules should be something like:
* up to C/5 at 10 C
* up to C/10 at 5 C
* up to C/20 at 0 C
* up to C/50 at -5 C
but I've never seen anything like that. And "0 deg C" is too round a number to be quite correct for anything other than freezing water. What gives?
 




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