This is a great Digital Battery Capacity Checker. Know your packs!

The battery analyzer  is a quick, convenient, easy-to-use device. The Digital Battery Capacity Checker is compatible with Lithium based batteries from 2S to 7S, and supports Nickel based batteries from 4 to 7 cells.

It shows at a glance the remaining capacity in your battery pack, cell balance, and other information you need to get the best performance and reliability from your batteries, and avoid costly mistakes. The large LCD display and capacity graphs are easy to read, and the SUPER low price of the Digital Battery Capacity Checker compared with the high cost of batteries make it a sure money-saving addition to every toolbox at the flying field, boat races, or car race track.