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Old Sep 06, 2009, 05:48 PM
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Maverickk's Avatar
Hawaii
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Question
Using A123 in Place of Lipo Batteries

I am interested in converting some of my planes over to take the A123 Li-Ion pack and was wondering if there are any tips on what differences I should expect when doing this. I am currently running 3S TP 2100mah packs and will buy the 3 cells of the A123 2300mah batteries and plan on making up some packs from these. I see that there will be about a 3oz weight penalty, but given the resilience and increased cycle lifespan and decreased fire hazard, it seems worth it.

Are there any other type of Li-Ion that have better performance then A123?

Also, any suggestion on a good cheap reliable source?

Thanks
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Old Sep 06, 2009, 06:29 PM
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Hi!

As a rule of thumb, 3s Lipo equals 4s A123 in voltage.

Look for the green cells on eBay, they get sold in China relly cheap now.
I also saw complete 4s packs really cheap.
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Old Sep 06, 2009, 06:46 PM
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Argentina, Buenos Aires
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To replace 3S lipo with 3S A123 you will need a hotter motor. A123 are really good, here is a blog to a similar conversion:

http://www.rcgroups.com/forums/showthread.php?t=1086226
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Old Sep 06, 2009, 07:21 PM
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Here is a whole Thread of A123 fueled aircraft.


http://www.rcgroups.com/forums/showthread.php?t=734064


Charles
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Old Sep 07, 2009, 02:34 AM
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As others have said, you usually need to increase the cell-count when using A123s because they're nominally 3.3v per cell compared with 3.7v per cell for LiPos.

But, depending what motor and prop you're currently using with your 3S LiPo, you may be able to use 3S A123 and get the same performance by tweaking the prop size to achieve the same watts (i.e. more amps than before, because of the reduced voltage) if your motor can handle the extra amps.

If you go for 4S A123 (the preferred route in my opinion), you may have to reduce your prop size so that your motor doesn't over-amp due to the extra volts (13.2v nominal compared with 11.1v for the LiPo).
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Old Sep 07, 2009, 03:36 AM
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Thanks for the replies - great info!

What is the recommended place for buying already-made packs - 3S and 4S?

Thanks again.
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Old Sep 07, 2009, 04:11 AM
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I found out, that it is safe to calculate 10V under load for both 3s Lipo and 4s A123.

A reputable source is http://battlepack.com/.

A cheap source would be this:
http://cgi.ebay.de/4S1P-LiFePO4-A123...d=p3286.c0.m14
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Old Sep 07, 2009, 08:42 PM
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Julez, thanks for the info.

What is a LiLo cell? Is the A123 considered a LiFe or a LiFePO4 cell?

I need to charge these on my Bantam BC6 charger and it does not list A123 or Li-Ion as a battery type, but it does have LiLo and LiFe.

I found another source for A123: www.tanicpacks.com This seems like a good source for ready-made packs.

Thanks
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Old Sep 08, 2009, 04:25 AM
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Quote:
What is a LiLo cell? Is the A123 considered a LiFe or a LiFePO4 cell?
LiLo?
Never heard of that. Maybe the font used does not distinguish between "L" and "I"?
There are 3 common types:

LiFe: LiFeP04, 3.6V max
LiIo: Lithium Ion, 4.1v max in the past, 4.2v possible.
LiPo: Lithium Polymer, 4.2V max.

A123 is LiFePo4, but they use a special formula for the stuff inside, which makes their product superior to anything else in the LiFePo4 market.
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Old Sep 08, 2009, 06:32 AM
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Try here for packs. I have had good luck with this company.http://www.radicalrc.com/shop/index.php?cat=199&
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Old Sep 08, 2009, 12:41 PM
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Quote:
Originally Posted by Maverickk
Julez, thanks for the info.

What is a LiLo cell? Is the A123 considered a LiFe or a LiFePO4 cell?

I need to charge these on my Bantam BC6 charger and it does not list A123 or Li-Ion as a battery type, but it does have LiLo and LiFe.

I found another source for A123: www.tanicpacks.com This seems like a good source for ready-made packs.

Thanks
Li-Fe is for the A123's. It is not Li-Lo, it is Li-Ion. Set the V Type in the Setup to Li-Fe for A123's.
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Old Sep 08, 2009, 02:21 PM
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Again, thanks for the info. Another question. If I use a standard Castle Creation TB56 with the LV cut off at 3S Lipo (9V) can I use this OK on a 4S A123 where the LV cut off should be at 8.8v?
Thanks
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Old Sep 08, 2009, 02:42 PM
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Quote:
Originally Posted by Maverickk
Again, thanks for the info. Another question. If I use a standard Castle Creation TB56 with the LV cut off at 3S Lipo (9V) can I use this OK on a 4S A123 where the LV cut off should be at 8.8v?
Thanks
I use 9V as the cutoff for my 4S A123 powered aircraft. They're the only packs that I own that I actually fly until I hit LVC or until I get a noticeable drop in performance. My setup draws ~45-50 amps wide open and 9V cutoff has been working great for me thus far. Will typically draw my packs down to 90-95% DOD when using 9V cutoff. Still gives me enough remaining capacity to set up and execute landing.

I personally would not go lower than this, at least in my application.

Mark
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Old Sep 08, 2009, 03:30 PM
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9.0V cutoff will work fine, if you see that you still have qyite a bit of unused capacity you can go lower, I usually use 2.0v per cell, but as mentioned be aware that when A123 dump, they really dump. You won't hurt the cells, and you will have full servo control but no thrust from the motor. electric dead stick..........

Brad
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Old Sep 14, 2009, 02:58 PM
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Maverickk's Avatar
Hawaii
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Julez, Thanks for the info.

What are the pro and cons of LiFe vs. LiIo? Someone brought to my attention some new Bosch power tool batteries that are called Litheon which they say are LiIo technology, but the cells I looked at are 1300mah at 4.3v and are only 37g each. This makes these batteries considerably higher power density then LiFePO4 batteries. Bosch also claims more than 5X the battery life over conventional LiIo batteries.

Thanks for the help.

Quote:
Originally Posted by Julez
LiLo?
Never heard of that. Maybe the font used does not distinguish between "L" and "I"?
There are 3 common types:

LiFe: LiFeP04, 3.6V max
LiIo: Lithium Ion, 4.1v max in the past, 4.2v possible.
LiPo: Lithium Polymer, 4.2V max.

A123 is LiFePo4, but they use a special formula for the stuff inside, which makes their product superior to anything else in the LiFePo4 market.
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