RE: LIPO
higher mah = longer runtimes, higher voltage, or the higher the number before he S, the faster you will go. 2S is 7.4 volts, which is a little more than a 6-cell nimh or nicd, 3s is 11.1 volts 4s is 14.8 and so on, increasing by 3.7 volts each time. One thing I would suggest it get a hardcase lipo. Is basically like the lipo in the link, but it has a hard protective plastic casing over it. Lipos are pretty soft and can be damaged fairly easily if they get hit hard on you chassis, or by rocks...but a hardcase lipo would be a little bigger and a little more expensive.