Battery Charger
A device used to put energy into a secondary cell or rechargeable battery by forcing an electric current through it.
A battery charger is an electrical device used to restore energy to a depleted automotive starter battery. It plugs into a standard wall outlet and delivers direct current (DC) at a regulated voltage to the battery terminals. Modern chargers are "smart" chargers, utilizing multi-stage microprocessors to automatically adjust the charging rate (amps) and voltage based on the battery's state of charge and chemistry type (such as AGM, Gel, or standard flooded lead-acid).
Smart chargers typically run through several phases: desulfation (to break down lead sulfate crystals on the plates), bulk charge (delivering high current), absorption (tapering current at a set voltage), and float/maintenance mode (trickle-charging to keep the battery at 100% without overcharging). Overcharging a battery can cause it to vent explosive hydrogen gas and boil off the internal electrolyte, permanently damaging the cells.
If a vehicle won't start due to a dead battery, a fast charger can boost it, but slow trickle charging (2 to 10 amps) is much safer and healthier for the battery's lifespan. Mechanics use heavy-duty wheeled charger-boosters that can also deliver high cranking amps to jump-start vehicles with deeply discharged batteries in the workshop.