A little bit of extra money will get you a much better charger:

http://www3.towerhobbies.com/cgi-bin...?&I=LXCTZ5&P=7

At $49.99, the Quick Field Charger Mk II can quick charge two batteries at once. It peak charges and autodetects when the peak is reached then switches to trickle charging for NiCd/NiMH batteries, so you don't have to sit by with a stop watch while charging batteries. It will also charge LiPo batteries and will work with a wide variety of balancing modules including the Electrifly Equinox balancing interface.

You can use the charger on your car battery or field box battery. It also works well with most any 12v power supply.

This is a very versatile charger and a bargain for the price. I also own the MRC Super Brain 989 that I use for cycling and testing purposes as well as trickle charging new packs. For the bulk of my daily quick charging needs though, my Hobbico Quick Field Charger MkII is my "go to" charger.