Tenergy TN138 4 Bay AA/AAA NiMH LED Battery Charger Insert 1 to 4 pieces of 1.2V AA/AAA rechargeable Ni-MH batteries into the battery compartment. Worldwide voltage for 100-240V AC input. Constant charging current mode; trickle current when fully charged. Eight hours charging time cut-off to ensure safety. Micro-processor control (-Delta V detection) which automatically controls the charging process.