Battery C Rating - The C rating of a battery (or cell) is used to indicate the continuous current draw (amps) the cell will support. By multiplying the C rating times the cell capacity in milliamperehours (mAh), the continuous current in milliamperes (mA) of a cell is easily calculated. Example - For a 2000 mAh battery with a 15C rating, the continuous current that may be drawn out of the battery is 2000 mAh x 15 = 30000 mA, or 30 Amps (A) (divide by 1000). There is also another rating that is applicable to a battery known as peak or "burst" current discharge rating. Peak current is higher than continuous C rating. It indicates that a battery will deliver higher current than the C rating for brief instances. For ease of calculations, LiPo Calc does not take peak current into account. This figure varies widely with battery type and in most applications is not required for calculating a suitable battery pack configuration. Instead, LiPo Calc calculates battery pack configurations such that current draw will never exceed the continous C rating of the battery. Of course, the calculation is only as good as the inputs supplied, so make certain to enter an accurate number in the Amps field. If you aren't sure how many amps your specific motor/prop/gear train configuration pulls, use an amp meter to measure the current draw between the motor and the ESC in static condition using a known good power source of approximately the same voltage as the LiPo configuration you intend to use. Put that number into the Amps field.