Depends on the charger. On iCharger DUOs you can discharge from one port through the second port to either another battery or a large resistor. On single port chargers that is how regenerative discharging works - you are wasting the discharged energy back into the power supply, which must be a battery capable of absorbing it. On single port ichargers you can also do a discharge+ discharge, which allows you to run a resistor bank inline with your charge leads to boost discharging capability, no matter what is on the power supply side of the charger.