More than likely you won't find what you are looking for at Radio Shack. If you have a way to discharge cells right now, you could hook a watt meter inbetween the cell(s) and the discharging device.
http://www.powerwerx.com/product.asp?ProdID=3809 It tells capacity, voltage, amps, and watts.
Instead, you
could buy a Duratrax ICE, which is a Lipo charger as well as NiMh and NiCd.
SH Z-Car, Custom Crawler, 8s Savage,
12s XTM XLB 1/7 buggy,
4wd 4-link rear/IFS Pro4 truck,
Custom Hyper 10 Short Course,
Belt-Drive Mammoth ST 1/8 truggy, 4s 17.5 MM Pro HPI Blitz