Car battery glossary
Plain-English definitions of car battery terms: AGM, EFB, Ah, CCA, battery registration, parasitic drain, JIS and DIN sizes, and more.
- Ah (amp-hour)
- Capacity: how much charge the battery stores. A 70Ah battery can in theory supply 3.5 amps for 20 hours. Match the factory figure; going lower shortens life.
- CCA (cold cranking amps)
- The current a battery can deliver for 30 seconds at −18°C while staying above 7.2V. It is a standard measure of starting power, even in a hot country.
- AGM
- Absorbent glass mat battery. The electrolyte is held in glass-fibre mats, so it is spill-proof and handles deep cycling. Required on many start-stop and German cars. Learn more
- EFB
- Enhanced flooded battery. A tougher flooded design for basic start-stop systems. You can upgrade EFB to AGM, but not the other way round.
- SMF (sealed maintenance-free)
- A conventional flooded lead-acid battery sealed so it never needs topping up. The standard battery in most cars without start-stop.
- Start-stop
- A system that switches the engine off when the car stops and restarts it when you move. It cycles the battery many times per trip, so it needs AGM or EFB.
- Battery registration
- Telling the car, with a diagnostic tool, that a new battery has been fitted so the charging system resets its ageing model. Needed on most BMW, Audi, VW and similar cars. Learn more
- IBS (intelligent battery sensor)
- A sensor on the negative terminal that measures current, voltage and temperature so the car can manage charging.
- Parasitic drain
- Current the car draws while locked. A small amount is normal; a faulty module or badly wired accessory can flatten a battery within days. Learn more
- State of health (SOH)
- A tester's estimate of how much of its original capability a battery has left. Below roughly 60% it is a replacement candidate in UAE heat.
- State of charge (SOC)
- How full the battery is right now. A healthy battery can still be flat; a full one can still be worn out.
- Jump start / boost
- Starting a car with a flat battery using an external power source such as a jump pack or another car. Learn more
- Jump points
- Dedicated positive and earth posts under the bonnet on cars whose battery sits in the boot or under a seat.
- Memory saver
- A small power supply plugged in while the battery is out, so the car keeps its settings and modules do not log faults.
- JIS size (e.g. 80D26L)
- The Japanese battery size code: performance rank, case class, length in cm and positive-terminal side.
- DIN / EN size (e.g. LN3, H6)
- European case sizes used by German, French and many newer Asian cars. LN1 is the smallest, LN6 the largest.
- BCI group (e.g. 48, 94R)
- The North American battery size standard used on American cars and trucks.
- Date code
- The manufacturing date stamped or printed on the battery. Fresh stock matters more in the UAE because heat ages batteries on the shelf too.
- 12V auxiliary battery
- The small battery in a hybrid or EV that runs the electronics and wakes the car up. It fails like any other 12V battery.
- Sulphation
- Lead sulphate crystals hardening on the plates when a battery sits discharged. The main reason a car left for weeks may never fully recover.
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