LiFePO4 batteries

[JS]

TA posted about LiFePO4 batteries a while ago.
Using the Tenergy 10AH batteries, I'm impressed. Lighter, longer lasting.
6 hours of ClearNav, 302, 6201 and TT21 brings two 10AH batteries "down" to 13.1V. The old SLA and AGM stuff I'd been using now seems rubbish.
The Lithium Phosphate batteries even use your existing chargers.
Jim

[T]

Are these batteries safer than the LiPo used in RC aircraft? There have been bad fires when charging LiPO and fireproof containers are recommended.
T

[CLewis95]

Can the LiPO batteries really be charged safely with the SLA Chargers we use?

[mattm...@gmail.com]

On Thursday, September 27, 2012 8:09:54 AM UTC-4, T wrote:
> Are these batteries safer than the LiPo used in RC aircraft? There have been bad fires when charging LiPO and fireproof containers are recommended.
>
> T

All that was hashed out on the previous discussion. These are different from
Lithium Phosphate and don't suffer the fire problems. I got one from K2 Energy
this year and love the lighter weight, higher voltage, and higher capacity.
I did get their charger also just to be sure.

-- Matt

[Evan Ludeman]

The RC model battery / fire starters are lithium polymer (LiPO). The
tenergy and K2 SLA replacement batteries are lithium iron phosphate
(LiFePO4). I saw a lot of the K2 batteries at my last contest, heard
only praise. I'm thinking of switching to the LiFePO4 batteries but
I'm in need of evidence that they'll work at typical glider discharge
rates (2A during TX, about 1A otherwise) when really cold (say -30
C). Any of you Sierra Wave guys using these?

[JS]

As Matt posted and I believe was in a "Soaring" article, LiFePO4 is a much better technology than the old LiPo or LiIon. There are videos of people trying to blow up LiFePO4 cells or saw them up on YouTube. They didn't make the Darwin Awards.
Each 12.8V battery pack that looks like your old 8AH SLA battery has a charge/discharge controller on board. Weighs 50% of the equivalent SLA battery.
Tenergy or K2 are available in the USA directly or from their resellers, mine from all-battery.com.
Airbatt is available in Europe from accu-24.de. One section of their online catalog lists them by sailplane model.
Jim

[Papa3]

Been using mine all year including early season, longish ridge missions on cold (though not bitterly cold) days. My load is pretty typical of a modern panel, with radio, xponder, vario, backup FR, and ClearNav. So far, the LiFePO4 batteries from K2 have performed flawlessy. I ran a discharge test on them under load on the bench earlier this year, and they met or exceeded the performance chart I had.

P3

[GM]

On Wednesday, September 26, 2012 11:29:19 PM UTC-4, JS wrote:
> TA posted about LiFePO4 batteries a while ago. Using the Tenergy 10AH batteries, I'm impressed. Lighter, longer lasting. 6 hours of ClearNav, 302, 6201 and TT21 brings two 10AH batteries "down" to 13.1V. The old SLA and AGM stuff I'd been using now seems rubbish. The Lithium Phosphate batteries even use your existing chargers. Jim

Have been using the K2 batteries for two years now and can say only good things about them. It may be noteworthy that K2 has now a 10Ah version out which has the same frame like the typical 7.5Ah SLA batteries.
Yes, these batteries will become unstable and can blow up - if you expose them to 400F for a long time - in which case you may have a far greater problem on your hands than worrying about your plane or battery! ;-)
GM

[Papa3]

On Thursday, September 27, 2012 7:54:50 PM UTC-4, Papa3 wrote:
>> Been using mine all year including early season, longish ridge missions on cold (though not bitterly cold) days. My load is pretty typical of a modern panel, with radio, xponder, vario, backup FR, and ClearNav. So far, the LiFePO4 batteries from K2 have performed flawlessy. I ran a discharge test on them under load on the bench earlier this year, and they met or exceeded the performance chart I had.
>
>
>
> P3

Someone asked me offline... I have two of the K2 10AH batteries on separate circuits. One battery lasts for a typical 5 hour flight, and for my longest flight this year (9 hours on a coldish ridge day) I switched over after 6 and still seemed to have some juice left on the battery when I switched.

[howdy]

This is what the inside of our K2 looks like. http://www.etotheipiplusone.net/?p=1991

[John Carlyle]

There are two versions of the K2 battery, one with (suffix EB) and one without (suffix E) the Battery Management System. From reading the technical literature, it sounds like the BMS is designed to prevent battery damage in high discharge or high charge rate situations. Since in a glider we're only discharging and charging at about 2 amps max, can do without the BMS? Or have I got it wrong and would be risking a fire?

-John

[Eric Greenwell]

I'd be inclined to get one with BMS, since there doesn't seem to be
anyway to equalize the battery cells without it; however, I can't find
any technical info on their site, so I'm just guessing. In fact, I can't
even find the one you are talking about on their site.

The lack of readily available info makes me bit leery about the product.
Any Li battery that is sold as a drop-in replacement for an SLA battery
should tell me a lot more about it than the price before I would put it
in my glider.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)

[jjbird]

I ran across this the other day when looking into these things...(almost) everything you never wanted to know about the K2
http://www.etotheipiplusone.net/?p=1991
and the datasheet...
http://www.houseofbatteries.com/documents/K2B12V7EB.pdf

The takeaway is that the BMS will do balancing so that you can use a normal SLA charger on it, the BMS will also provide output protection for under-voltage or over-current situations (though if your panel manages to pull 24A battery damage is likely low on the worry list). The BMS however, doesn't seem to provide any input current/voltage protection.

I'm no expert on battery charge profiles, so it isn't clear to me whether the BMS will turn random SLA charger output into a proper LiFePO4 profile. My understanding is that an SLA charger should do the job. What I don't know is whether or not it would have an impact on the maximum charge state or cycle lifetime, it'll take someone more knowledgeable about batteries than me to answer that.

[Uncle Fuzzy]

Just anecdotal... one of my RC flying buddies wanted high capacity in an un-finicky rechargeable battery, so he chose LiFeP04. He uses them in an RC plan that draws in excess of 40 amps at full throttle. He has over 600 cyles on the battery pack so far. His charging system is a piece of lamp cord cut to a length that delivers his desired charge current. His source: battery packs for cordless power tools. His thinking was that if it can handle the current draw of a 10" circular saw, it could handle his RC plane.

[John Carlyle]

I wrote to K2 Energy regarding the Battery Management System used with their LiFePo4 battery. In my e-mail, I gave typical glider battery usage:

1) charging the K2B12V10 batteries inside a home environment with normal SLA chargers at 1.0 A maximum.

2) in-glider average current draw of 1 A, rising to 2.5 A when transmitting and the transponder is being pinged.

3) in-flight use in a 0 deg F to 110 deg F temperature range.

K2's answer was "Purchase the K2B12V10EB (with BMS). It will give you more cycle life and is well worth the extra few dollars. The current draw is no problem. Our battery with BMS is rated for 25A continuous."

Hope this helps someone. The extra weight and flat power delivery aren't big enough problems for me that I can justify spending $180 per battery when a SLA of similar capacity goes for $20.

-John

[JohnDeRosa]

On Wednesday, October 10, 2012 9:04:15 PM UTC-5, Uncle Fuzzy wrote:

"His charging system is a piece of lamp cord cut to a length that delivers his desired charge current."

Huh? The wire length limits the charge current? I may be dense but you are going to have to explain this to me a bit more.

[bruced...@gmail.com]

The Lithium Phosphate batteries even use your existing chargers.
Jim

********
This is correct. I bought a K2 w/o the BMS this year. I already owned a few Battery Tender Jr. chargers, so I emailed K2 and Battery Tender. Both replied the charger was fine for a K2. I was concerned about the lack of BMS and bought a K2 charger to conduct my own tests, so if anyone wants this $50 charger at a discount, let me know.
~Bruce

[dbra...@gmail.com]

On Thursday, October 11, 2012 3:39:55 PM UTC-7, bruced...@gmail.com wrote:
> The Lithium Phosphate batteries even use your existing chargers. Jim ******** This is correct. I bought a K2 w/o the BMS this year. I already owned a few Battery Tender Jr. chargers, so I emailed K2 and Battery Tender. Both replied the charger was fine for a K2. I was concerned about the lack of BMS and bought a K2 charger to conduct my own tests, so if anyone wants this $50 charger at a discount, let me know. ~Bruce

hmmm, I wouldnt use existing/old style chargers on LifePo or A123. You really should use a balance charger which monitors the voltage of each cell during charge. This will help avoid ruining your nice new battery. I presume the K2 has a balance plug?

[Uncle Fuzzy]

Wire has resistance, enough wire (his cord is approximately 30 feet long)has enough resistance to drop the charge current to his target 10 amps. That's an extrememly mild charge rate for an A123 cell pack that will happily discharge at 80 amps.

[bruced...@gmail.com]

> hmmm, I wouldnt use existing/old style chargers on LifePo or A123. You really should use a balance charger which monitors the voltage of each cell during charge. This will help avoid ruining your nice new battery. I presume the K2 has a balance plug?

My K2 w/o BMS has just two terminals just like any Pb acid, so I don't see how a charger can monitor each cell. I also don't know what a balance plug is, so I'll stop commenting. I'm just relaying what K2 and B-T Jr. told me.

[Eric Greenwell]

Was that cheaper than buying a charger? Even if the wire was free, I
think it'd be safer and cheaper in the long run to buy a charger that
was smarter than a piece of wire.

[Don Johnstone]

How else would you control current other than with an appropriate
length/size of wire? You can if you wish coil it and package it and call it
a resistor.

[Eric Greenwell]

Perhaps he is able and willing to stand by the battery and monitor the
process, but I'd rather buy a charger: it could regulate the current,
measure the amp hours delivered, and shut down automatically when the
battery is fully charged or the time has run out.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to

email me)nz

[Dan Marotta]

I'm still having trouble with the concept of charging a battery with AC
power. I saw no mention of a rectifier... Maybe he flip-flops the wires 60
times per second?


"Eric Greenwell" <ow...@thegreenwells.netto> wrote in message
news:k5cg9m$i9r$1...@speranza.aioe.org...

[dbra...@gmail.com]

On Thursday, October 11, 2012 7:25:17 PM UTC-7, bruced...@gmail.com wrote:
> > My K2 w/o BMS has just two terminals just like any Pb acid, so I don't see how a charger can monitor each cell. I also don't know what a balance plug is, so I'll stop commenting. I'm just relaying what K2 and B-T Jr. told me.

Okay, perhaps when they assemble/manufacture these batteries they ensure the cells are very well matched. The typical A123 and LiFe batteries used in RC have a special plug, often a JST-XH/(JR in the case of ElectroDynamics) type that allows the cells to be balance charged when using a capable charger. It is an absolute must in the case of Lipos (for safety)but with Life/LifePo/A123 you can get away without balance charging to some degree.

[Uncle Fuzzy]

On Saturday, October 13, 2012 1:17:23 PM UTC-7, Dan Marotta wrote:
> I'm still having trouble with the concept of charging a battery with AC
>
> power. I saw no mention of a rectifier... Maybe he flip-flops the wires 60
>
> times per second?
>
>
>
>
>
> "Eric Greenwell" <ow...@thegreenwells.netto> wrote in message

Okay, now I see your confusion. Based on a lack of information in my post. My mistake. He's connecting his 3 cell LiFePo to a car battery, using the 30(ish) feet of zip cord as a dropping resistor (I just talked to him today, last year he got fancy and added a springwound cutoff timer). I was just trying to point out that the A123 cells are pretty robust, and while using the recommended charger and charge profile will likely lead to the longest possible life of your LiFePo batteries, he's been beating the hell out of the same 3 battery packs for 2+ years now, and has subjected them to more cycles than I would be able to put on a battery used in my glider in 5 years.

[cernauta]

On Thu, 11 Oct 2012 17:55:20 -0700 (PDT), dbra...@gmail.com wrote:

>hmmm, I wouldnt use existing/old style chargers on LifePo or A123. You really should use a balance charger which monitors the voltage of each cell during charge. This will help avoid ruining your nice new battery. I presume the K2 has a balance plug?

the electronics for charge regulation and balancing are built into the
battery case of the SLA replacement sets. So, just two terminals.
That's all

aldo cernezzi