Hi, I recently bought and EF yak 88" and I have a question about the batteries that I want to use to power the receiver. I want to use 2 batteries since I want to be sure that everything runs good. I have a 7.4 volt 2900 mah A123 that I use with a regulator to power the receiver, the plane flies good with that package but I want to have another one on the plane. The other battery that I have is a 6 volt JR NiMH receiver battery. Now, my question is wheter I can use both of these batteries to power my receiver or do I need to use same two batteries like two 7.4 volt 2900 mah A123. Do they both need to be li-pos or can they be mixed?Thanks

i don't think i would run them like that unless it was through a regulator. the only reason i say this is because the two batteries have different voltage when charged and i don't know if that would cause any stress on one battery or not. like it trying to charge the other. i would just get 2 1100a123's and run them on the reciever. can be purchased for $60. or just use the one a123. but i to like alittle redundency. but i wouldn't mix the two.

I never heard of 7.4V 2900 mah A123. Are you sure that's what it is? Usually they are 6.6V 2300mah or 6.6V 1100 mah.

Yes, sorry it is a 6.6V 2300mah and it is connected to a regulator

I would just buy another A123. No need to regulate them either

Originally Posted by flatspinjim

I would just buy another A123. No need to regulate them either

Samolocik, no need to regulate is true, but also make sure you are using good servos that will handle the power without frying up.

Well, I checked the battery again and the one that I will use is a Duralite 2900mah 4 Cell Li-Ion 7.4Volt the other battery that I mentioned is in my other plane. Sorry for the confusion but I was writing the post in a hurry.So her is my question again, the 2900 mah battery that I have, I use with a regulator and the other battery I have is 6 volt JR NiMH receiver battery. Can I combine those to power my receiver without any problems or should I just buy another Duralite battery?thanks and once again sorry for the confusion.

No, those batteries are different voltages. It's OK (but not common) to use different batteries in parallel of different capacities, but they should always be the same nominal voltage. It might work if the regulator output is the same voltage as the NiMh, but it's not a good idea, and it would be, in my opinion, less safe than your current configuration.

On a 50CC airplane, one battery should be fine, but if you really want the piece of mind of two batteries, they should be ideally be identical batteries/regs. If you want a nice and safe option, just run two 1100 A123's with seperate switches. There should be plenty of capacity with no regs to fail and some redundancy.

i don't know for 100% but i think if you would use the li-ion on a reg and the nimh, the reciever will pull from the nimh first because it has a higher voltage, but i don't know if it would back feed into the reg unless there is a diode to stop the voltage to back feed. i would just get 2 1100mah a123's and you will be safe. or just use the lion and a reg or a dual reg on the one battery for a little safety in case a reg fails.

ok, I will not risk mixing those batteries, thank you all for your help

i think you made a good call. i would not want to risk a $2k plane over $60 in batteries.

If you have a Fromeco Wolverine switch you can use whichever two batteries you like, it has a built in battery share. If not I'd match the batteries.

*Edit* I should clarify, you still have to regulate the batteries into your receiver (if thats what you planned on doing), but the batteries can be different types and capacity. Check this diagram from Fromeco:

thanks for the diagram, but I'm still going to stick to buying another duralite battery

Hey, i got an idea from a friend and bought a 4800mAh Li-phos from TBM and cut it apart and made 2 2400mAh packs for my RX.
Now i have 2 6.6volt batterys for my reciever .
Thier regular price i think is $56. but is now on sale for $19.95
for 4800mAh battery that is cheap !
or you can cut the scrink wrap and fold them in half.
thier 10.5in long and i think 1.25" round.
but you will have to buy a charger to charge them.
I purchased mine from Radical RC for $68
It beat what other people are doing with the Dewalt batterys for over $100 and cutting them apart.