LifePo4 replacement for Lipo

[mariosnic]

Hello Everyone,

First I want to say thanks to Bruce for his wonderful site and the
valuable info. As I have been a r/c plane builder (not flyer) in the
past, I recently decided to take up the hobby again and become a flyer
as well.

Due to time constraints I deciced to an ARF plane from HK. I got all
cheap intro parts from there, except the battery.

As I mentioned above, since I haven't been following the hobby for a
long time, I had a lot of info to digest, plus I have not been
involved in battery operated models before. The point that baffled me
is LiPo batteries and their dangers. Because of that I decided to
build a LifePo4 battery pack for the plane, to replace the 11.1V
1100mAh 3S1P LiPo pack.

My question is:

If I create a 3S pack from A123 26650A Cells will it work, or I will
need another battery configuration / make changes to ESC to make this
work?

Thanks in advance,

Mariosnic

[Curtis]

Hi,
First of all, don't be worried about Lipos. There are thousands of
people using them and the dangers are there, but they are
exagerated.
Secondly, you certainly can do what you plan on doing with the Lifepo
batteries. There are two drawbacks to this method however. One is
the weight, the Lifepo packs are a bit heavier (about 25-50%), and the
second is the fact that the nominal voltage of the Lifepo cell is 3.3V
vs. 3.7V of the Lipo. This will reduce your nominal voltage of your
pack by 1.2 volts. I wouldn't worry about this, though as you should
still have enough power to fly the plane with it.

Now, when you are building your pack, you said you are using 26650
cells, which I believe are 2300 mah cells. This will give you more
than twice the capacity of the original 1100 mah Lipo cells. One
concern I have is now you are using cell that weight more Mah/Mah and
more than doubling your pack size. What this will do is create a
battery that may be 2.5 times the weight of the recommended Lipo
pack. You may not be able to fly the airplane under these conditions.

Good Luck,
Curtis

[mariosnic]

Thanks a lot Curtis.

All suggestions are welcome!!

Thanks again for the feedback!

Marios

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[JomarX]

Just a quick note, A123 cells have lower nominal voltage than the Lipo
cells (lipo = 3.7v, while A123 = 3.3v). So its fully charged voltage
'might' not be enough for your plane.... Not to mention it 'might' be
too heavy..

[mariosnic]

Thanks JomarX.

I got the suggestion to add a fourth cell to the pack to compensate...
But that adds another 40g, making the model 100g "overweight" that in
its specs... Being a foamy, that might be an issue.

I think I will try just to see if it can work...