View Full Version : A Simple Question About LiFePO4 Batteries
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
On Friday, May 11, 2018 at 3:37:03 PM UTC-4, 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
You don't want to drain an SLA all the way, as that shortens its life considerably. But you can drain a lithium battery "all the way" (to the point where the protection circuitry prevents further discharge) with not much loss of battery life. Thus for example a 7AH lithium battery will offer more usable capacity than a 10AH SLA. Except that you say you replace the SLA "every year or two", so perhaps you do discharge it deeply, or don't care about the longevity. SLAs are still so much cheaper than lithium batteries that so far I've stuck to SLAs, although I use them for 3-4 years. Those extra-large SLAs may be more expensive than the standard sizes, though?
I don't usually drain them. I switch to the backup if I'm on a long flight or it's cold. Rarely does the main batt go low enough to get the "low battery" warning blinking (11.2v). They don't cost that much more than the standard-size SLA battery. And they probably last 3 years on average, IIRC. I haven't done any testing nor do I write a date on them when installed. I just usually replace them when I have to start going to the backup on long flights.
So I'm surprised that a relatively new battery (2 seasons?) hasn't performed that well in two flights this spring. The last time, I decided to stay with SLA because it had worked well enough in the past and was a lot cheaper. But now that I'm facing replacement again so soon, I'm reconsidering.
Chip Bearden
Tango Eight
May 11th 18, 10:45 PM
A g a i n ?
The -only- advantage of SLA is lower purchase price. And considering that "7 AH" is really about 3.5 useful, the "economy" here is dubious, at best.
A good battery is $100.
Some problems are hard to solve. Not this one.
best,
Evan Ludeman / T8
kinsell
May 12th 18, 12:14 AM
On 05/11/2018 02:28 PM, wrote:
>But you can drain a lithium battery "all the way" (to the point
where the protection circuitry prevents further discharge) with not much
loss of battery life.
This assumes that all lithium batteries have a full-featured BMS circuit
that protects against battery abuse. That seems to be a bad assumption,
particularly for LiFePO4 batteries. Pfiffner has posted some
interesting failures he's seen there, in the previous incarnation of
this discussion.
Do it. Im using the Australian made Fusion battery, 10ah, and approved by the GFA.
1500 FULL DISCARGE CYCLES, 2500 80% discharge, will probably outlast my ability to fly.
Discharging an SLA more than 50% damages it, fully flattening them kills them completely.
On Saturday, May 12, 2018 at 7:00:52 AM UTC+10, wrote:
> I don't usually drain them. I switch to the backup if I'm on a long flight or it's cold. Rarely does the main batt go low enough to get the "low battery" warning blinking (11.2v). They don't cost that much more than the standard-size SLA battery. And they probably last 3 years on average, IIRC. I haven't done any testing nor do I write a date on them when installed. I just usually replace them when I have to start going to the backup on long flights.
>
> So I'm surprised that a relatively new battery (2 seasons?) hasn't performed that well in two flights this spring. The last time, I decided to stay with SLA because it had worked well enough in the past and was a lot cheaper. But now that I'm facing replacement again so soon, I'm reconsidering.
>
> Chip Bearden
You may well be discharging your battery more deeply than you think, hence the short life. 11.2v open circuit for a SLA is well below fully discharged at around 11.7 to 11.8V open circuit, but your meter is probably showing you the voltage with a load on so you really don't know how deeply discharged the battery is. If you want to check the actual approximate state of charge, put a multimeter on the battery after it is disconnected from all loads.. The table in the following article shows an approximation of state of charge based on open circuit voltage (from 100% @ 12.7+V to 0% at 11.8V) for various types of LA batteries.
> You may well be discharging your battery more deeply than you think, hence the short life. 11.2v open circuit for a SLA is well below fully discharged at around 11.7 to 11.8V open circuit, but your meter is probably showing you the voltage with a load on so you really don't know how deeply discharged the battery is. If you want to check the actual approximate state of charge, put a multimeter on the battery after it is disconnected from all loads. The table in the following article shows an approximation of state of charge based on open circuit voltage (from 100% @ 12.7+V to 0% at 11.8V) for various types of LA batteries.
Doh. Forgot the link. https://www.energymatters.com.au/components/battery-voltage-discharge/
JS[_5_]
May 12th 18, 01:08 AM
Chip, I think that QV (Richard's first ASG29, not Al's) had the same batteries when I bought it.
There were custom made hold-down straps.
I replaced the AGMs with 10Ah LiFePO4 and use the factory hold-down straps.
That larger battery size is unusual, haven't seen LiFePO4s that size.
Jim
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
On Friday, May 11, 2018 at 7:35:08 PM UTC-4, wrote:
> Do it. Im using the Australian made Fusion battery, 10ah, and approved by the GFA.
> 1500 FULL DISCARGE CYCLES, 2500 80% discharge, will probably outlast my ability to fly.
> Discharging an SLA more than 50% damages it, fully flattening them kills them completely.
Would be nice if you could actually get those 1500 discharge cycles, but I expect the battery will die from "old age" well before then, even with light use. How many years a LiFePO4 battery will really last is still a mystery, although some people "here" can report what, 6 or 7 years and still OK?
I have no reason to doubt the manufaturers claims, can you present any actual facts?
kinsell
May 12th 18, 04:45 AM
On 05/11/2018 01:37 PM, wrote:
> 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. :)
>
If you have to replace batteries every year or two, you must be using
some crap brand like Werker or PowerSonic (sounds almost like Panasonic!)
On Friday, May 11, 2018 at 7:15:02 PM UTC-4, kinsell wrote:
> This assumes that all lithium batteries have a full-featured BMS circuit
> that protects against battery abuse. That seems to be a bad assumption,
> particularly for LiFePO4 batteries. Pfiffner has posted some
> interesting failures he's seen there, in the previous incarnation of
> this discussion.
I really was just asking about the taller size battery (the PowerSonic # is PS-12100H if you want to look it up; it's about $10 more than the usual size) to see if there were a LiFePO4 equivalent.
That said, I've read Richard's posts as well as others from a few pilots who have reported relatively premature deterioration of LiFePO4 batteries. The verdict seemed very clear a few years ago. Now...? Having a $35 SLA start to slide after a few years wouldn't be as annoying as would a $100 to $150 LiFePO4 battery. Yes, the only advantage of SLA is cost...but if I have to replace both types at about the same time, that's definitive for me.
T8, I believe you were using Bioenno whereas most posts are about K2, with a few about Starkpower and one unanswered query about Dakota. I take it you're still happy with yours.
Chip Bearden
krasw
May 12th 18, 07:18 AM
On Saturday, 12 May 2018 06:16:40 UTC+3, wrote:
> I have no reason to doubt the manufaturers claims, can you present any actual facts?
My LFP batteries died in 1,5 and 3 years age, respectively. They have cycle life and calendar life. For glider pilots calendar life is what matters, we do not use 1000 cycles per year. Obviously not all LFPs are the same.
Try the Australian made Fusion brand, no cheap chinese junk. Fusion use prismatic cells, not round cheap laptop cells.
They also have very good internal battery management. They are the ONLY LiFe battery approved for gliders in Australia.
I have quality laptop batteries that are 10 years old, 1500 and 90% charge still.
Its all about the quality, just as a cheap SLA wont last, neither will a cheap LiFe.
Tango Eight
May 12th 18, 03:28 PM
On Friday, May 11, 2018 at 11:59:03 PM UTC-4, wrote:
> On Friday, May 11, 2018 at 7:15:02 PM UTC-4, kinsell wrote:
> > This assumes that all lithium batteries have a full-featured BMS circuit
> > that protects against battery abuse. That seems to be a bad assumption,
> > particularly for LiFePO4 batteries. Pfiffner has posted some
> > interesting failures he's seen there, in the previous incarnation of
> > this discussion.
>
> I really was just asking about the taller size battery (the PowerSonic # is PS-12100H if you want to look it up; it's about $10 more than the usual size) to see if there were a LiFePO4 equivalent.
>
> That said, I've read Richard's posts as well as others from a few pilots who have reported relatively premature deterioration of LiFePO4 batteries. The verdict seemed very clear a few years ago. Now...? Having a $35 SLA start to slide after a few years wouldn't be as annoying as would a $100 to $150 LiFePO4 battery. Yes, the only advantage of SLA is cost...but if I have to replace both types at about the same time, that's definitive for me.
>
> T8, I believe you were using Bioenno whereas most posts are about K2, with a few about Starkpower and one unanswered query about Dakota. I take it you're still happy with yours.
>
> Chip Bearden
I agree that there seems to be a wide range of quality out there and that higher price doesn't guarantee longevity (K2). Several guys have the Bioenno 12 AH battery. I know of no issues, but it's a very small sample (also worth noting the obvious fact that this technology is still evolving). I reported my test results earlier this Spring... 11.5 AH capacity after five seasons of use.
What we don't have a handle on is what all the eventual failure modes are. If it turns out that they frequently die suddenly, or sometimes die in some hazardous fashion, then that would take some of the luster off!
I may well replace mine after this season out of caution. I'm more concerned with performance and reliability than economy when it comes to batteries. I'll offer the old one for $25 so someone else can brag on economy :-).
best,
Evan Ludeman / T8
Clay[_5_]
May 12th 18, 03:37 PM
I have three K2s, one is completely useless the other two provide performance similar to SLA at best. All are 2-5 years old, I've always used the K2 charger. Borrowed a friend's Stark recently, voltage was much better throughout the flight. FWIW
Jim White[_3_]
May 13th 18, 07:53 AM
I bought A123. Low power rating but still giving after 3 years.
I have several LFP batteries, all different makes. The multiple chargers was an issue for me. I have had a very good experience with the CTEK Lithium US charger.
I was curious about CTEK since both of my newest cars came with CTEK trickle chargers, a Mercedes and a Porsche. I find it unusual that different manufacturers would use a common product.
I have been using the CTEK Lithium US for about one year. One charger for all my batteries and everything has been working perfectly.
Check it out. One charger works for all LFP batteries from 5Ah to 60Ah.
JS[_5_]
May 13th 18, 05:44 PM
On Sunday, May 13, 2018 at 6:38:32 AM UTC-7, wrote:
> I have several LFP batteries, all different makes. The multiple chargers was an issue for me. I have had a very good experience with the CTEK Lithium US charger.
> I was curious about CTEK since both of my newest cars came with CTEK trickle chargers, a Mercedes and a Porsche. I find it unusual that different manufacturers would use a common product.
> I have been using the CTEK Lithium US for about one year. One charger for all my batteries and everything has been working perfectly.
> Check it out. One charger works for all LFP batteries from 5Ah to 60Ah.
The Tenergy TB6AC+80W works well with all the LiFePO4s I've connected.
It can be used with other chemistries too, including SLA/AGM, LiPO, Li-Ion at various cell counts (voltages).
For reference, that charger is provided with Jonkers sailplanes with the jet sustainer. The battery for that system is a Tenergy 12v 10Ah.
The references to the Australian LiFePO4 battery are interesting. GFA has only authorised that particular battery and the use of an inappropriate charger with it. I pointed this out to the CTOA.
Those Fusion batteries have not self-destructed when charged with a car charger. But they haven't been charged fully either.
Jim
Im getting full charges from the recommended Repco charger.
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.
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.
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
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
kinsell
May 17th 18, 12:16 AM
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.
Richard Pfiffner[_2_]
May 17th 18, 12:51 AM
On Wednesday, May 16, 2018 at 4:16:35 PM UTC-7, 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.
Some valid comparisons on this page;
http://www.craggyaero.com/lifepo_battery.htm
Richard
www.craggyaero.com
Dan Marotta
May 17th 18, 02:13 AM
My observations were purely subjective:Â* With SLA batteries, I would run
out of power in 3-5 hours.Â* With LiFePO4 batteries, my volt meter still
showed good voltage after 5 hours.Â* 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.Â* Not everybody of course.
>
>
--
Dan, 5J
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 Marotta
May 17th 18, 02:44 PM
I never paid attention to the voltage vs temperature thing, but my
engineering training says that you are correct, Dr. Guy.Â* As to the full
voltage thing with the Li batteries, yes, they hold full voltage...Â*
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.Â* 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.Â* 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.Â* Never a problem.Â* 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
Papa3[_2_]
May 17th 18, 03:37 PM
On Tuesday, May 15, 2018 at 11:59:54 PM UTC-4, wrote:
> 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
The first "actual" answer to the specific question - and it only took 20 some-odd messages to get it :-)
I took apart a commercially built "drop in replacement" LiFePo4 battery a couple of years ago, and my sense was that there was a bit of wasted space. I suspect the idea was to provide a capacity and footprint that was identical to the SLA batteries they replaced. I did the same googling when I was in the market, and I didn't find anything with significantly more than 10ah stated capacity in the same footprint.
FWIW, I run a load test of my LiFePo4s at the beginning of every season. My K2s currently show about 9.4-9.5 Ah at 0.1c discharge rate. What is remarkable is how flat the voltage drop is in comparison to the old SLA/AGM batteries. (Dick's post above shows a graph).
My K2s are both 4 years old. I did have one go south, but it was stored fully/deeply discharged after a long end-of season ridge mission. K2 gave me a partial credit for a replacement even though it was stored against their recommendations.
FWIW
P3
On Thursday, May 17, 2018 at 10:38:00 AM UTC-4, Papa3 wrote:
> On Tuesday, May 15, 2018 at 11:59:54 PM UTC-4, wrote:
> > 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
>
> The first "actual" answer to the specific question - and it only took 20 some-odd messages to get it :-)
>
> I took apart a commercially built "drop in replacement" LiFePo4 battery a couple of years ago, and my sense was that there was a bit of wasted space. I suspect the idea was to provide a capacity and footprint that was identical to the SLA batteries they replaced. I did the same googling when I was in the market, and I didn't find anything with significantly more than 10ah stated capacity in the same footprint.
>
> FWIW, I run a load test of my LiFePo4s at the beginning of every season. My K2s currently show about 9.4-9.5 Ah at 0.1c discharge rate. What is remarkable is how flat the voltage drop is in comparison to the old SLA/AGM batteries. (Dick's post above shows a graph).
>
> My K2s are both 4 years old. I did have one go south, but it was stored fully/deeply discharged after a long end-of season ridge mission. K2 gave me a partial credit for a replacement even though it was stored against their recommendations.
>
> FWIW
>
> P3
Not sure how that answered the original question. But I am intrigued with the possibility of building my own pack. Not sure I'd trust that for flying, but perhaps for earthly pursuits. It's easy to wrap up the cells in a sloppy mess of tape. But can one get a ready-made casing that is similar to the SLA batteries? Or, can somebody with a dead LiFePO4 battery send it to me so I can put new cells inside?
Martin Gregorie[_6_]
May 17th 18, 04:31 PM
On Thu, 17 May 2018 07:57:20 -0700, moshe.braner wrote:
> Not sure how that answered the original question. But I am intrigued
> with the possibility of building my own pack. Not sure I'd trust that
> for flying, but perhaps for earthly pursuits. It's easy to wrap up the
> cells in a sloppy mess of tape. But can one get a ready-made casing
> that is similar to the SLA batteries? Or, can somebody with a dead
> LiFePO4 battery send it to me so I can put new cells inside?
>
If you're reasonably handy with a 'Junior hacksaw' or similar fine-
toothed tool and with using rapid setting epoxy, then making a container
with the same dimensions as the SLA you're replacing is fairly easy. Make
it from 1/16" (1.5mm) epoxy plate), possible with hardwood of epoxy rod
in the corners. If you can't find it locally, epoxy plate can be sourced
from:
http://www.cstsales.com/
--
Martin | martin at
Gregorie | gregorie dot org
JS[_5_]
May 17th 18, 04:44 PM
If you'd like to build your own, BatterySpace.com seems a good place to start.
The wasted space issue is overcome by using prismatic shaped cells, at least in the quality units.
Greg used two flat clear pvc plates for top and bottom hot glued the round cells, 8 I believe, in stagared with two end clear pvc and bms board large shrink tubing over it all for the long sides and . It has held up now for two seasons without problems. He also bought a battery welder to connect the cell together.
On Thursday, May 17, 2018 at 5:29:29 AM UTC-7, 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.
This LiFPO battery shows a significant a temperature dependence of voltage:
https://www.batteryspace.com/prod-specs/9055.pdf
Basically, all chemical reactions are very temperature dependent.
Tom
> However, I can't find a LiFePO4 equivalent for it. Does such a thing exist?
How about this one?
https://www.batteryspace.com/lifepo4-battery-12v-10ah-120wh-40a-rate---replace-sla-12v-10ah-with-5-times-cycle-life-lighter-weight---un38-3-passed-dgr.aspx
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?
Richard Pfiffner[_2_]
May 18th 18, 04:21 PM
On Friday, May 18, 2018 at 8:05:47 AM UTC-7, 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?
I have a MicroAir and it works great with a LIFEFO4 battery.
Richard
www.craggyaero.com
Charlie M. (UH & 002 owner/pilot)
May 18th 18, 05:27 PM
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.
Tom Kelley #711
May 18th 18, 06:16 PM
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/collections/12v-series-lifepo4-batteries/products/12v-9ah-lfp-battery-abs-sealed-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.
Richard Pfiffner[_2_]
May 18th 18, 06:56 PM
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/collections/12v-series-lifepo4-batteries/products/12v-9ah-lfp-battery-abs-sealed-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
Richard Pfiffner[_2_]
May 18th 18, 07:01 PM
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/collections/12v-series-lifepo4-batteries/products/12v-9ah-lfp-battery-abs-sealed-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
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-battery-12v-10ah-120wh-40a-rate---replace-sla-12v-10ah-with-5-times-cycle-life-lighter-weight---un38-3-passed-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
How about this one?
https://www.batteryspace.com/lifepo4-battery-12v-10ah-120wh-40a-rate---replace-sla-12v-10ah-with-5-times-cycle-life-lighter-weight---un38-3-passed-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/lascar-panel-instrument-emv-1125/)
Tango Eight
May 19th 18, 01:38 PM
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
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.
kinsell
May 23rd 18, 02:51 PM
On 05/17/2018 06:29 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.
>
Hmm. Flying (legally) up to 18K at other locations, I've never seen
SLA's drop voltage and then recover when they warmed up. With an
adequate battery, they don't drop below 12 even when transmitting on the
radio.
LiFePO4 batteries aren't exactly immune from the cold, both the Antares
and the Perlan 2 gliders have battery heaters that are used to preheat
on the ground, and then again in the air as needed. Using battery power
to heat in the air is better than just letting them get cold. If
;you've got enough extra capacity to get through long flights, that's
great, but so do I with SLA's.
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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