SMC 20C 11.1V LiPo HArd case 37.74 Wh

[BrianG]

It's a little device that plugs inline between the battery and ESC which measures voltage and current samples. After a run, you hook it to your PC, download the data from it, and look at the graphs. Those graphs will show you how the batteries are performing (by looking at the voltage drop when the current spikes hit). Here's a link: http://www.eagletreesystems.com/MicroPower/micro.htm