Bosch BC3680 36V Lithium-Ion Battery Charger Charges a spent 36-Volt 4.0 Ah battery in 45 minutes Charges a spent 2.0 Ah 36-Volt battery in 35 minutes Cooling fan protects heavy-duty batteries from overheating while charging Trickle charge for cell protection - 80 percent fast charge, 20 percent normal charge Compatible with 18-Volt Bosch batteries