Features Adopting Japanese high performance Li-ion (Li-Mn) battery. Built in protection device to prevent battery overcharge and over discharge. The latch design increases intensity and convenience when assembling or dismantling the rechargeable battery from the cordless screwdriver. Fully charged voltage: 21V, low-voltage protection: 13.5V, over-temperature protection (discharge): 72。C . Battery ID identification design, which only allows original charge station to recharge the battery to secure battery safety and extend battery lifetime.