A car battery stores electrical energy in chemical form and releases it when needed. Passenger cars usually use 12-volt lead-acid batteries. Its main job is to supply the starter motor with hundreds of amps for a few seconds to crank the engine.
What does a battery do?
- Starts the engine by powering the starter motor.
- Powers lights, alarm, infotainment and control units while the engine is off.
- Stabilises voltage while the alternator is charging, protecting sensitive electronics.
Battery types
- SLI: conventional battery for cars without start-stop (e.g. MOLL SLI classic).
- EFB: enhanced flooded battery for basic start-stop systems.
- AGM: absorbent glass mat battery for advanced start-stop with brake energy recovery.
- AFB: MOLL's start-stop battery developed as a direct alternative to AGM.
Signs of a failing battery
- Slow or difficult cranking, especially on cold mornings
- Dim headlights and dashboard lights
- Battery warning light or start-stop not working
- Swollen case or corroded terminals
A rested, fully charged battery should read about 12.6–12.8 V; below 12.0 V it is discharged. Average battery life is 3–5 years.
Frequently asked questions
How often should a car battery be replaced?
Typically every 3–5 years, depending on usage, climate and the health of the charging system.
Can I fit a standard battery to a start-stop car?
No. Start-stop vehicles need EFB, AGM or AFB batteries designed for frequent cycling.
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