Roger, I am using two battery pacin order to keep my boaton the water as long as possible, I was A VICTIM OF THE SIZE OF CARRIER I HADIN MY CUPBOARDi HAD ONE THAT HELD 4 aaa Cells, and another that held 4 AA cells. into these, I put cells that I had hanging around, and they have done very well. I buy my consumables from a company that supplies us at work namely Certified Precision Components ltd., and they have been stocking Ni MH batteries for a long time,so I use 1000 mA/H cells in the AAA holder, and 1500mA/H in the AA size holdereach of those combinations copes equally well with the job of running the receiver and servos,and there is no BEC on my speed controllerso I would say to you go for 2300mA/H AA cells like ashley said, and keep them constantly at full charge, but keep an eye open for one of the cute new generation of battery chargers that charge your cells until a certain volts per cell threshhold has been reachedat which point the charger turns the wick down and just provides a keep alive voltage or a one millisecond pulse across the cellsevery so often, That set up should keep you going for a good long while unless you leave the cells in a discharged state for too long. Failing that, you could get a 12 volt gell cell lead acid battery and a n electronic speed controlwith a battery elimination outputand an in line fuse for the positive supply at ten amps. I n cases like this, I recommend that modellers experiment at home with a lash up including an accurate ammeter to see what current the motor draws or both motors draw under normal running loads, but if you have seen whateffect a bunch of algae has when wrapped round a prop,you would want to be preparedwith a 15 and 20 amp fuse as well in your bits box. Another quite important tip I give modellers is to ensure that your spare sets of crystals are indeed sets and that they work together, make sure that they operate your radio gear correctly when installed in the transmitter and receiverbecause there’s nothing worse than seeing your precious model chuntering off downwind whilst you franticly crank the servo sticks and nothing happens. Get it right first time, remember "No mistakes is No Accident"., and remember Proper Planning Prevents Pretty Poor Performance……………………………Mike Davidson  in Plymouth