You want an AC/DC or "Dual Power" charger - it will run on AC at home and the alligator clips will let you run it on DC at the track. There are a bunch of good ones available. Hobbypartz has two that are good, inexpensive chargers, good for getting a start in lipo - Here's one -

http://www.hobbypartz.com/skychb6chdup.html

The other is the Thunder AC-6,

http://www.hobbypartz.com/thac6smbachw.html


Both are balancing chargers and will handle just about all batt chemistries.