REDLITHIUM USB (universal serial bus) charger charges the Milwaukee REDLITHIUM USB battery. A 2.1 Amp charge rate delivers up to 3 times faster charge time. Get 50% of a charge in under 30 minutes, 80% in under one hour, and a full charge in 2 hours. Conveniently charge REDLITHIUM USB batteries via Micro-USB Cable from a wall plug or USB power source. 2 year warranty.