Experience with Lithium Iron Phosphate Glider batteries?

I have been using the factory installed Strobel solar system on my 29 with K2 batteries for the past 4 years without issue. The Strobel controller was designed for Lead-acid chemistry and the K2's "can" be charged by lead-acid chargers due to their lower output voltage. That being said, the 13,75 Volt output of lead-acid systems won't charge the LiFePo to it's full capacity that needs 14.6 V.

On Wednesday, 18 May 2016 22:35:08 UTC+3, jfitch wrote:

Agreed - it's worth checking the battery you buy if it is an unknown brand.

I bought one of these "brand" batteries from Aeroakku.com (german shop specializing aviation batteries). It died after one year use because BMS electronics self-destructed, non repairable. The shop promptly informed me that their warranty is SIX MONTHS. After some heated emails they were kind enough to not send me bill for checking what went wrong with the faulty battery (yes they tried to do that at first), and offered me a whopping 10% discount on next battery. After that I learned that Aeroakku battery came from no-name-factory in China, as I quess most of LiFePos, with Aeroakku-sticker on top of it. Recently I bought another no-name Lifepo from another webshop who offers industry standard 2 year warranty for their products, for roughly half the price.

At 00:01 20 May 2016, Dave Springford wrote:
I have been using the factory installed Strobel solar system on my 29
with
=
K2 batteries for the past 4 years without issue. The Strobel controller
wa=
s designed for Lead-acid chemistry and the K2's "can" be charged by
lead-ac=
id chargers due to their lower output voltage. That being said, the
13,75
=
Volt output of lead-acid systems won't charge the LiFePo to it's full
capac=
ity that needs 14.6 V.


David,
Find yourself a good electronics hobbyist who understands charging
circuits,
it should be a simple job to tweak the regulator voltage so it fully
charges
your LiFe battery, (provided the circuitry is not encapsulated or potted)
however if you do this then CLEARLY mark it as modified because it will
potentially kill SLA batteries after a short time, if you were in the UK I
would
offer to look at this for you, however posting it to and from the US is
impractical.
Ben.

On Friday, May 20, 2016 at 11:15:08 AM UTC-7, Benedict Smith wrote:
At 00:01 20 May 2016, Dave Springford wrote:
I have been using the factory installed Strobel solar system on my 29
with
=
K2 batteries for the past 4 years without issue. The Strobel controller
wa=
s designed for Lead-acid chemistry and the K2's "can" be charged by
lead-ac=
id chargers due to their lower output voltage. That being said, the
13,75
=
Volt output of lead-acid systems won't charge the LiFePo to it's full
capac=
ity that needs 14.6 V.


David,
Find yourself a good electronics hobbyist who understands charging
circuits,
it should be a simple job to tweak the regulator voltage so it fully
charges
your LiFe battery, (provided the circuitry is not encapsulated or potted)
however if you do this then CLEARLY mark it as modified because it will
potentially kill SLA batteries after a short time, if you were in the UK I
would
offer to look at this for you, however posting it to and from the US is
impractical.
Ben.

14.0V will be sufficient to fully charge a LiFePO4 battery. 14.6 will do it faster, but is a little harder on them. 13.8 won't get them to fully charged. Yes, I know what the specs say from the retailers, but I have also seen the test results. You do not what to "float" charge a LiFePo4 battery, but if you are using an SLA charger that floats at 13.6 or 13.8 it won't harm them, because charging will be effectively terminated at float voltage.

Has anyone else tried the Shorai LiFeP motorcycle starter batteries. I put a 36 aH one in my Goldwing and was so blown away with it I bought an 18 aH for my Ventus. It is still amazing after three years. Buy the charger with it and forget about electronics shops. Ok it is not the perfect form & fit of the old gel cells, but it fits in the double slot where I used to have two gel cells and easily outperforms both of them by a lot. It is great having better than 13 volts with an SN-10 all day long. I use a 2nd 14aH to run my transponder which lasts for days. Not cheap, but cost is nothing compared to the years of headaches with gel cells.

On Friday, May 20, 2016 at 3:34:11 PM UTC-7, wrote:
Has anyone else tried the Shorai LiFeP motorcycle starter batteries. I put a 36 aH one in my Goldwing and was so blown away with it I bought an 18 aH for my Ventus. It is still amazing after three years. Buy the charger with it and forget about electronics shops. Ok it is not the perfect form & fit of the old gel cells, but it fits in the double slot where I used to have two gel cells and easily outperforms both of them by a lot. It is great having better than 13 volts with an SN-10 all day long. I use a 2nd 14aH to run my transponder which lasts for days. Not cheap, but cost is nothing compared to the years of headaches with gel cells.

I would not recommend the Shorai starter batteries for instrument power. These are an example of the "lead acid equivalent AH" that have become popular in the Lithium business. In an engine start application, the AH requirement is quite small, what you need is a very high current for a very short time. Taking advantage of this and the high current capability of very small lithium cells, suppliers like Shorai are building batteries with the high current required, but very low capacity to save money. It works fine for starting your motorcycle, but does not have the same capacity if low current for long time periods are the application. Shorai themselves explain "PBeq AHr" he

http://shoraipower.com/faq

For instruments, you want real AH capacity, not "equivalent". One tipoff when you are looking at specs is the weight: a LiFePO4 battery will weigh about half of what an SLA weighs in the same real capacity. If it is less than that, either it isn't really the same capacity, or they have made a major technological breakthrough. Nothing wrong with Shorai for what they were made for, but for a glider you are better off with a K2 or Starkpower or similar.

thanks Ben,

I've thought of that too, but I don't know if the Stobl has an adjustable voltage regulator or if everything is all sealed up. I need to look under the panel. In the meantime, it keeps the batteries going for longer than I can fly in a day!

On Friday, May 20, 2016 at 4:39:37 PM UTC-4, jfitch wrote:
On Friday, May 20, 2016 at 11:15:08 AM UTC-7, Benedict Smith wrote:
At 00:01 20 May 2016, Dave Springford wrote:
I have been using the factory installed Strobel solar system on my 29
with
=
K2 batteries for the past 4 years without issue. The Strobel controller
wa=
s designed for Lead-acid chemistry and the K2's "can" be charged by
lead-ac=
id chargers due to their lower output voltage. That being said, the
13,75
=
Volt output of lead-acid systems won't charge the LiFePo to it's full
capac=
ity that needs 14.6 V.


David,
Find yourself a good electronics hobbyist who understands charging
circuits,
it should be a simple job to tweak the regulator voltage so it fully
charges
your LiFe battery, (provided the circuitry is not encapsulated or potted)
however if you do this then CLEARLY mark it as modified because it will
potentially kill SLA batteries after a short time, if you were in the UK I
would
offer to look at this for you, however posting it to and from the US is
impractical.
Ben.

14.0V will be sufficient to fully charge a LiFePO4 battery. 14.6 will do it faster, but is a little harder on them. 13.8 won't get them to fully charged. Yes, I know what the specs say from the retailers, but I have also seen the test results. You do not what to "float" charge a LiFePo4 battery, but if you are using an SLA charger that floats at 13.6 or 13.8 it won't harm them, because charging will be effectively terminated at float voltage.

Combining my experience and most everything I've read, LiFePO4 chemistry is not meant to be trickle charged as typical solar panel/charger would provide. LiFePO4 extended life cycles (some claim 2000 or more) depend on deep discharges (like 70% to 80% of capacity) then being fully recharged. If you want to depend on solar charging perhaps it would be better to stay with battery chemistry which likes trickle charging (such as SLA or AGM). FWIW...down the road my guess there will be purpose built LiFePO4 solar chargers which do not initiate charging until the LiFePO4 battery has used 70%-80% of its capacity.

On Sunday, May 22, 2016 at 6:49:11 PM UTC-7, wrote:

Combining my experience and most everything I've read, LiFePO4 chemistry is not meant to be trickle charged as typical solar panel/charger would provide. LiFePO4 extended life cycles (some claim 2000 or more) depend on deep discharges (like 70% to 80% of capacity) then being fully recharged. If you want to depend on solar charging perhaps it would be better to stay with battery chemistry which likes trickle charging (such as SLA or AGM). FWIW....down the road my guess there will be purpose built LiFePO4 solar chargers which do not initiate charging until the LiFePO4 battery has used 70%-80% of its capacity."

LiFePO4 batteries don't need to be deeply discharged and are "happy" with even light discharge charge cycles. And while it's true, it's preferable to store these batteries at a lower voltage that fully charged (for longest life), that's not always practical (though some chargers have a setting to maintain them at the lower storage voltage (the Shorai I installed in my Honda S2000 has a charger that does that). In any case, you can swap out the solar charge controller in your glider for one that's designed for LFP batteries like this one: http://www.amazon.com/Bioenno-Power-...roller+lifepo4

Some thoughts:

life of batteries: Number of cycles is not an issue for most. How many times do you fly in a year? Even if 50 times (I wish!) it would take 4 years to use up the 200 cycles life of a lead-acid battery, and by then it would deteriorate anyway due to time alone. Even the Lithium battery is going to die after a decade or so, thus will never even get close to the promised 2000 cycles.

capacity: in my case, I find that a small 4 or 5 AH battery suffices, even for a 6-hour flight. OK, I don't have FLARM nor a transponder. And my computer is a Nook e-reader, drawing about 1/4 amp. YMMV.

cost: I considered a LiFePo battery last year when I needed to replace my SLA battery (again), but found that they are still about $150, and I got _three_ new small (4 or 5 AH) SLAs for a total of $27 including the shipping (from Apex). The weight of such is similar to the weight of a (larger) LiFePo battery, and for my needs, the capacity is sufficient (see above). A larger SLA is not expensive either, but does add a few pounds.

solar panel in glider: don't think of it as a charger for the battery. Rather, is helps supply the ongoing current to the always-on (while flying) gizmos, reducing the load on the battery (possibly to zero when you are not talking on the radio). You do need something that will prevent overcharge if the glider sits in the sun a while, but a charge controller designed for SLA is fine for that. Worry about fully recharging the battery only when you take it home. (Unless you want to avoid having to take it home.)

A 10-watt solar panel is fairly large, presumably it's the flexible type, glued onto the outside of the glider? I've considered adding a smaller panel inside the cockpit, presumably on the glare shield above the instruments, but doing the math convinced me that it's not worth the trouble, as it would only stretch the battery capacity a modest amount. It's easier to just get a larger battery. (Also, a panel on the glare shield may reflect sunshine into the pilot's eyes, directly, or reflected again via the canopy.)