The dcb119 li ion battery charger from dewalt not only charges 12v amp 20v xr li ion batteries quickly and easily using your in car 12v socket it also diagnoses any potential problems with such batteries informing the user of issues such as power problems overheating or cold batteries the dcb119 also shuts off automatically protecting the health of your battery meaning this charger not only informs the user that a battery may be coming to the end of it39s lifespan it extends the life