1. Engine off – The battery provides energy to operate lighting and accessories.
2. Engine starting – The battery provides energy to operate the starter motor and ignition system during starting.
3. Engine running – The charging system provides most of the energy required with the engine running; the battery acts as a voltage stabilizer to protect voltage sensitive circuits, particularly digital circuits.
1. Lead-Acid – Virtually all automotive batteries are lead-acid batteries. Two different metals, both lead compounds, are immersed in an acid electrolyte. The chemical reaction produced provides electrical energy.
2. Low Maintenance/No Maintenance – Some manufacturers use this terminology. “Low maintenance” means that electrolyte can be added. “No maintenance” means that the battery is sealed.
3. Vented – Most batteries have removable vented caps that are used to check electrolyte level and add distilled water as necessary to restore the level. The caps also allow hydrogen gas, a byproduct of battery charging, to escape during charging.
4. Sealed – Some lead-acid batteries are sealed, that is, there are no removable caps to check electrolyte or replenish it. Some of these batteries have s small “eye” to indicate charge level. Still others are sealed, but include connections to external vent tubes.
NOTE:- For all types of batteries, always follow the manufacturers recommendations for charging and testing.