This battery charger will charge most 3.7V Lithium batteries including 21700, 18650, 20700, 26650 and more. Will charge two of our fully discharged 18650 3500ma batteries in about 2.5 hours and 21700 5000ma batteries in about 3.5 hours when using the AC or DC adapters. This is one of the fastest chargers on the market and our fastest charger. Most competitors chargers take about 6-8 hours to charge our 18650 3500ma batteries and 8-10 hours to cha