The Tenergy 12-bay charger has a battery reconditioning feature, which can be applied by pressing the button on the charger marked "refresh". This will discharge and recharge the batteries completely, "reconditioning" them. This function is useful if you have old batteries that have not been used for a long time, or batteries that have been frequently drained only partially.
If you are using flowlights or other products until the batteries "die" there is no need to refresh them. The "memory" effect in NiMH batteries is almost non-existent and applies more to NiCd batteries, which we do not recommend using and are no longer common anyway.