C-rate

For a 2,000 mAh battery, 1C is 2 A and 0.5C is 1 A. Battery datasheets use C-rate to specify maximum continuous and peak currents for charge and discharge. Higher rates deliver more power but generate more heat, reduce the capacity actually delivered and usually shorten cycle life. Typical energy-type lithium-ion cells are charged at or below about 1C, while high-power cells are built for high discharge rates at the expense of energy density.

Where it bites: motor starts, radio transmissions and heaters create short current peaks that can exceed a small battery's rating, causing voltage sag and resets even when the average power looks fine.