Batteries > Li-Poly

Q-17: I’ve already built your Scratch One electric-powered sailplane design that appeared in the November 2003 MA and it flies great! But with all the talk now of Li-Poly batteries, can I change over to these new cells in my Scratch One? Answer ...

Q-83: With all the advantages being pointed out concerning Li-Poly batteries for electric-powered flight, I wondered if these same batteries might be put to good use powering RC systems used to control fueled-engine aircraft? Is there some way I might use several Li-Poly batteries to power my RC receiver and servos? Would there be any advantage in doing that? Answer ...

Q-42: I purchased a TUBBY CUBBY by Wattage (Global Hobby Distributors). It comes with a 370 electric motor, 3.7/1 gear box and a 7.5 x 5 propeller. I’m using an FMA Direct M5 receiver and two FMA Direct PS-20 servos. The ESC is a Castle Creations Pixie-7P programmed to cut off at 6.0 volts. Power is provided by a two-cell Kokam 700 mAh Li-Poly battery. The problem is that at about 1/3 throttle, the motor cuts off. What is wrong and how can I correct it? Answer ...

Q-45: I want to replace an 8-cell NiMH battery pack (nominal 9.6 volts) with a 2-cell Li-Poly battery pack (nominal 7.4 volts). I realize that the voltage will be lower, so I want to know if it is okay to add 2 NiMH from my surplus supply and place them in series with the 2 Li-Poly cells. That ought to get me close to the desired 9.6 volts. Since I’ll be using part NiMH cells in this pack, is it okay for me to use my peak detect charger? Answer ...

Q-59: I read that you must set your Li-Poly battery charger to the number of cells being charged (although some chargers will do this automatically). The large chargers that I see advertised have a 10-11 cell maximum capacity. How do you charge a 3S4P Li-Poly battery pack that has a total of 12 cells? Do you have to use two chargers or can a 10-11 cell charger handle the extra cell? Answer ...

Q-86: I intend to purchase two sets of Li-Poly batteries from a local hobby shop. Each set has three cells in series. I plan to connect each three-cell pack in parallel to increase the capacity, so I will end up with what you would designate as a “3S2P” pack. The cells of this pack are rated a 2100 mAh capacity and have a load capability of 20C. When I use this pack in my aircraft—six cells all together—the total capacity will be 4200 mAh (2 X 2100). My question is, can I charge the entire pack as one 4200 pack, or must I charge them separately? Answer ...

Q-115:  I wonder what the shelf life of the new Li-Poly batteries is as compared to the NiMH batteries? Also I have read that some of these new Li-Poly batteries might possibly explode and that has me concerned about my safety. What are your thoughts on this? Answer ...

Q-118: I’ve been using the popular ElectriCalc computer program to help me make choices in electric power systems for my model aircraft. A fellow modeler told me recently that there is a program available that will also let me select particular Li-Poly battery configurations to suit my model needs. Can you refer me to this program? Answer ...