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A Simple Question About LiFePO4 Batteries



 
 
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  #21  
Old May 14th 18, 02:39 AM posted to rec.aviation.soaring
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Default A Simple Question About LiFePO4 Batteries

Im getting full charges from the recommended Repco charger.
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  #22  
Old May 14th 18, 08:30 AM posted to rec.aviation.soaring
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Default A Simple Question About LiFePO4 Batteries

On Friday, May 11, 2018 at 12:37:03 PM UTC-7, 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


If it's working for you and if there are no readily available replacements just keep using the SLA/AGM battery you already use. Personally I like the K2 batteries and the one in my ship is starting it's fifth year of service but it's not magic, just a good battery that fits my needs well. In the case of my glider it solved a space, weight and capacity requirement but it seems that the SLA/AGM is doing everything you need it to do.
  #23  
Old May 15th 18, 01:25 AM posted to rec.aviation.soaring
SF
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Default A Simple Question About LiFePO4 Batteries

Money isn't everything. However your lifetime allotment of cussing is a precious thing, not to be wasted on SLA batteries.

SF

The request was for a simple answer, so here ya go. I could have made it simpler, but I'm saving my allotment for windy contest days which I have grown to hate with a passion usually reserved for people driving slowly in the left lane.
  #24  
Old May 15th 18, 08:35 PM posted to rec.aviation.soaring
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Default A Simple Question About LiFePO4 Batteries

I got my simple answer about the apparently non-existent larger size LiFePO4 battery.

Regarding the ensuing discussion, I didn't go the LiFePO4 route a few years ago even though the sentiment at the time seemed to "it's a no brainer; just do it." The current sentiment seems to be a bit more nuanced, which is good to know. Thx, all, for the candid inputs.

Chip Bearden
  #25  
Old May 16th 18, 04:59 AM posted to rec.aviation.soaring
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Default A Simple Question About LiFePO4 Batteries

I have a friend that built several, 4 two for him and two for me 13.2 volt 11AH lifepo4 that used round cells and a bms circuit. for about $50 each that was the same size as the standard 12volt 7ah agm. They went with my Ventus but was a great system. Now I have to talk him into building a few more for my 27 although the 27 came with two lifepo4's one K2 and one bienno both look a few years old and have great capacity so far.

CH
  #28  
Old May 17th 18, 02:13 AM posted to rec.aviation.soaring
Dan Marotta
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Default A Simple Question About LiFePO4 Batteries

My observations were purely subjective:* With SLA batteries, I would run
out of power in 3-5 hours.* With LiFePO4 batteries, my volt meter still
showed good voltage after 5 hours.* No hard numbers, I know, but I got
the performance that I required.

On 5/16/2018 5:16 PM, kinsell wrote:
On 05/15/2018 01:35 PM, wrote:
I got my simple answer about the apparently non-existent larger size
LiFePO4 battery.

Regarding the ensuing discussion, I didn't go the LiFePO4 route a few
years ago even though the sentiment at the time seemed to "it's a no
brainer; just do it." The current sentiment seems to be a bit more
nuanced, which is good to know. Thx, all, for the candid inputs.

Chip Bearden


Right, some people are discovering that comparing preposterously
optimistic data sheet numbers of lithium batteries against actual
performance of SLA's isn't a valid comparison.* Not everybody of course.



--
Dan, 5J
  #29  
Old May 17th 18, 01:29 PM posted to rec.aviation.soaring
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Default A Simple Question About LiFePO4 Batteries

I want to concur with Dan.
I fly out of Minden and we cruise between 15,000 and 17,999. It is COLD at that altitude.
My lead batteries would lose voltage as the temp dropped. After three hours at altitude they were lucky to put out 11 volts. Of course, when the batteries warmed up alter landing they had full voltage.
The LiFePO4 batteries do not seem to affected by cold soak. They work the whole flight at full voltage.
  #30  
Old May 17th 18, 02:44 PM posted to rec.aviation.soaring
Dan Marotta
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Default A Simple Question About LiFePO4 Batteries

I never paid attention to the voltage vs temperature thing, but my
engineering training says that you are correct, Dr. Guy.* As to the full
voltage thing with the Li batteries, yes, they hold full voltage...*
Until they don't, and then they simply turn off, they don't run at
reduced power output as the SLAs do.

With the SLA batteries, I always used two batteries on a typical flight
in the Rockies, usually switching at around 3 hours.* With the LiFePO4,
I would easily run 5 hours and never have to switch, though, since I had
a separate tail battery, I kept a fully charged battery there.* And, as
I've said before on this group, after watching the batteries carefully
while charging on the concrete floor of my garage, I took the big step
after a year of leaving them installed in the glider with the proper
charger attached and plugged in.* Never a problem.* Your results may vary.

On 5/17/2018 6:29 AM, wrote:
I want to concur with Dan.
I fly out of Minden and we cruise between 15,000 and 17,999. It is COLD at that altitude.
My lead batteries would lose voltage as the temp dropped. After three hours at altitude they were lucky to put out 11 volts. Of course, when the batteries warmed up alter landing they had full voltage.
The LiFePO4 batteries do not seem to affected by cold soak. They work the whole flight at full voltage.


--
Dan, 5J
 




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