AC to DC: 100-240V wide input voltage with US plug , output 21V 1A with 5% tolerance both for lithium ion battery charger. Using for most chainsaw batteries which full power is 21V or or 5 series battery pack. Please do NOT charge battery of max voltage below 21V, which may cause battery damage. LED light indication: when LED indicate light is RED, battery is in charging status; BLUE light is for full-charged. Commonly DC power connector: Male+Female Adapter 2.1 X 5.5MM DC Power Jack Plug Connector. Safe using: Built-in stable performance chips and protection cicuit, protect the battery from overheat, overcharging, over current, and short circuit. AC to DC Powertool Battery Charger