For the type of currents we are drawing you don't have to know too much about lipo batteries.

I had the problem of charging 3 x 3 cell packs for a large electric scale model. After looking at
all the fancy, big cell number chargers I ended up buying a couple of these cheapy chargers.

http://www.hobbyking.com/hobbycity/s.../Charger_2S~4S

They charge each cell individually through the balance plug on the battery so the charge is balanced &
it also indicates the battery charge as a percentage of capacity (the discharge curve on a lipo is almost
linear.) Works a treat on my 2 cell lipo ECU pack, simple to use (just set the current to one of three values,
for yours it would be 2 amps) & costs peanuts. Charges up to 4 cells. I take it your lipo has a balance plug?,
most current generation lipos do, worst case scenario you may need an adapter lead for the balance plug,
Hobby King carries them too. - John.