The NITECORE D4 Digital Battery Charger is a universal smart charger compatible with almost all cylindrical rechargeable batteries, thus eliminating the need to own several chargers. The D4 automatically detects Li-ion, Ni-MH and Ni-Cd batteries, and through manual selection is also capable of charging LiFePO4 batteries. Intelligent charging circuitry selects the optimal charging mode (CC, CV and dV/dt) for a given battery and each of the D4s two microcomputer-controlled charging slots then monitors and charges the battery independently. Charges four batteries at once.Furthermore, an integrated digital LCD screen clearly displays charging progress, voltage, current and time while an intelligent automatic power-off function terminates current when charging is complete. The Nitecore D4: The worlds most advanced fully-automatic digital charger. Its as simple as insert, detect and charge. We highly recommend this for flashlight users.