What size battery
 

I am new to this board and just getting back into RC Airplanes I was into the the gas models when I quit a few years ago Stoped by A Hobby shop A few weeks ago and purchased A Superstar EP I had not flown for a while and never flown electric I cycled my pack the Plane flew excellent I ended Up getting A 3300 nimh battery back I get about 10 to 15 minutes with this pack running a great planes Gear Driver, 600 Reverse motor and bigger prop and wheels but I would like more Flight time I have been Reseaching theese new Lithuim Pack which I know Will Give me more time and will need A different charger My question is What size Pack Do I need that would work in this plane Any help would be greatly appreciated. Thanks

RE: What size battery
 

Converting to LiPoly is not terribly complicated. You want to match Volts for Volts, then get enough capacity to handle the current draw from the motor AND give you the length of flights you want.

The stock pack is a 7-cell NiCd, 8.4 Volts nominally, 1.2 Volts per cell. What you'll find is that under load, the cells are only putting out about 1 to 1.1 Volts each, so the pack is only holding about 7-7.7 Volts when the motor is powered up.

LiPolys are 3.7 Volts per cell nominally, but, since you can't stress them as heavily as NiCd or NiMH, they hold their voltage better under load. So, a properly sized LiPoly pack will hold close to its nominal voltage under load.

In practical applications, a 2S (2 cells in series) LiPoly pack is a good drop-in replacement for a 7-cell NiCd or NiMH (7.4 Volts vs. 7-7.7 Volts, pretty comparable). So, whatever pack you choose will have a "2S" designation involved.

All that's left is to determine capacity, mAh. If you want to roughly double your flight time, double the mAh. That'd be 6600mAh if we're talking about the 3300mAh NiMH cells. Whatever cell type you choose, you simply stack enough 2S packs in parallel to get the capacity you want. For example, three 2S 2000mAh packs in parallel will give you 6000mAh. The designation for such a conglomeration would be 2S3P.

RE: What size battery
 

Matt said: "The designation for such a conglomeration would be 3S2P. " I think you tried to say 2S3P ... ?

RE: What size battery
 

Yes, yes I did. I'll fix it.

RE: What size battery
 

This is probably a silly question, but as long as the voltage stays close, how you get to the increased mah doesn't matter right? for example, instead of taking 3 2s 2000 mah packs, you could just take 2 2s 3000 mah packs?

RE: What size battery
 

mtomas: of course it is correct, only a small problem still here; you won`t find that big cells yet. Hard to find more capasity today than 2500mAh (FlightPower) in single cells. Therefore the use of parallell.
I looked up the the new ThunderPower 4S8000mAh LiPo, it is in fact 4S4P... Will rather go for 2 of 4S5000 FlightPower now, coupled in serie giving me 8S5000. These are 4S2P in fact, but i get only half the number of cells (16) which can cause trouble ;)