In such cases, press and hold the MODE button for five seconds to switch between 6V and 12V. This feature is designed to protect the battery from overcharging. It is compatible with all 6V/12V lead-acid, SLA, VRLA, GEL, AGM and wet. batteries.
Smart 4-Slot Battery Charger Multiple Protection for 21700 18650 AA Ni-MH Batter
Smart 4Slot Battery Charger Multiple Protection for 16340 18650 AA Ni-MH Battery
6V/12V 1.5A Multiple Protection Lead-Acid Battery Charger smart Pulse Repair