A battery can store a certain amount of energy which is called battery capacity. Low quality power adapters (voltage regulators or distributors) lose an unnecessary large part of this energy supply by converting it to thermal energy, this is called a power leak.

Power adapters which work with batteries should have very low power consumption, allowing more power to reach equipment.

The following situations can serve as indications of a power leak:

1. A battery runs out faster than it should (estimated running time can be obtained by working out battery capacity divided by combined average power consumption of all devices plugged in).

2. A battery shuts down whilst continuing to indicate remaining power. This may indicate a severe power leak on the adapter or one of the devices.