Due to different test methods, the internal resistance of the battery is divided into DC internal resistance and AC internal resistance. DC internal resistance is the battery internal resistance measured by the instantaneous DC discharge method, and AC internal resistance is the battery internal resistance measured by the AC injection or discharge method.

Under normal circumstances, the battery with small internal resistance has a strong high-current discharge capacity, while the battery with large internal resistance has a weak discharge capacity. When the battery is in different power state, its internal resistance value is different; when the battery is in different service life state, its internal resistance value is also different.