The latest generation of Nickel Metal Hydride batteries incorporate a new chemistry mandated to be more environmentally friendly. These batteries when charged with peak detection fast chargers have tendencies to false peak (not fully charge) repeatedly. These include all brands of NiMh batteries. If using NiMh packs be especially cautious when charging making absolutely sure that the battery is fully charged. It is recommended to use a charger that can display total charge current. Note the number of mAh put into a discharged pack to verify it has been charged to capacity.