Transponders are quickly charged with the convenient charging cradle. Max charge time is ~ 3 hours. Typical charge time is ~ 1 hour. LED lights on the transponder indicate full charge while in the charging cradle. When removed from the cradle the transponder green LED indicates approximate number of days of battery life left (up to 7 days). A red LED indicates when the transponder charge has less than 1 day remaining. SUPPORTS ORIGINAL RECHARGEABLE TRANSPONDERS ONLY.