The internal resistance of a source of electrical energy is an important factor when considering how to get the source to deliver maximum power to an electrical appliance (the load) connected to it. High-voltage power supplies, on the other hand, must have an extremely high internal resistance in order to limit the amount of current that would flow in the event of an accidental short-circuit. The internal resistance of a battery cell increases with an increase in distance between two electrodes. As the battery is discharged the electrolyte concentration is reduced, becoming pure water when the battery is fully discharged. Because of this change in electrolyte concentration the battery resistance increases during discharge.