Feature: Short circuit, over-charge, and over-heat protection,very safe. After fully charged one t
ime, can keep about months.Noraml use can keep 3-5years. Start car at one time on cold & hot areas.
Very connvenient.can be charge at home(100-240V) and car. Safety hammer for knock glass when meet e
p to positive wire,black clamp to negative wire.please make sure there is enough contact surfaces.