Car Battery and Roadside Glossary
Thirty-seven terms from battery labels, fitment charts and workshop invoices, each explained in two or three sentences. No sales copy, just what the word means and why it matters to your car.
Battery basics
6The numbers printed on the label, and what each of them is actually measuring.
Ampere-hourAh
The amount of charge a battery holds. A 70Ah battery can in theory supply 70 amps for one hour, or 7 amps for ten. It is the figure most often quoted when a battery is described by size, and a replacement should match or exceed what the car was built around.
Cold cranking ampsCCA
How much current a battery can deliver for 30 seconds in the cold while still holding a usable voltage. It measures starting muscle rather than capacity. The rating matters less here than in a cold country, but it is still what a fitment chart quotes and what separates two batteries of the same ampere-hour rating.
Reserve capacity
How many minutes a fully charged battery can run the car's electrics on its own if the alternator stops. It is quoted in minutes rather than ampere-hours, and it is the number that tells you how far you could limp home with a dead charging system.
State of charge
How full the battery is at this moment, expressed as a percentage. It is not the same thing as health: a worn battery can read fully charged and still fail to turn the engine, which is why a proper tester measures both.
Group size
The standard code describing a battery's dimensions, terminal positions and hold-down type. It is what makes a battery physically fit the tray and the clamp. Two batteries with the same ampere-hour rating and different group sizes are not interchangeable.
Terminal polarity
Which side the positive post sits on when you face the battery. Get it wrong and the cables will not reach, which is why the same model is sold in left hand and right hand versions and why a fitment lookup asks for it.
Types and technology
7Why two batteries that fit the same tray can be built in entirely different ways.
Flooded battery
The traditional lead-acid design, with the plates standing in liquid electrolyte. It is the cheapest to buy and still the right choice for an older car with no engine stop-start system and modest electrical demands.
AGMAbsorbent glass mat
A sealed lead-acid battery in which the electrolyte is held in a glass fibre mat rather than sloshing about as liquid. It tolerates deep discharge and repeated stop-start cycling far better than a flooded battery, which is why most modern cars with engine stop-start are built around one.
EFBEnhanced flooded battery
A flooded battery reinforced for stop-start duty, sitting between a plain flooded battery and an AGM in both price and endurance. A car specified with an EFB can usually be upgraded to AGM; a car specified with AGM should not be downgraded to EFB.
Start-stop battery
A battery rated for the hundreds of extra engine starts a stop-start system makes in a single journey. In practice that means an EFB or an AGM. An ordinary flooded battery fitted to a stop-start car wears out in a fraction of its normal life.
Auxiliary battery
A second, smaller battery that keeps selected systems alive while the main battery is busy starting the engine or is switched off. Common on German cars, often tucked under a seat or behind a wing panel, and it carries its own rating and its own failure mode.
48V mild-hybrid battery
A separate lithium pack running a 48 volt circuit alongside the car's normal 12 volt one, feeding a starter generator that restarts the engine and assists it under load. The car still has a conventional 12 volt battery as well, and the two do entirely different jobs.
Lithium starter battery
A lightweight lithium battery used in place of lead-acid, mostly on performance cars where the weight saving is the point. It needs a charging system designed for it, and it must never be boosted from a conventional pack without checking what the car expects.
Parts around the battery
6The battery is one component in a circuit. These are the others that decide whether it works.
Alternator
The generator driven by the engine belt that recharges the battery and powers the car while it runs. The battery only has to start the engine; from that moment on, the alternator is doing the work.
Learn more: Alternator and dynamo repairStarter motor
The electric motor that turns the engine over until it fires. It draws the largest single current in the car, which is why a weakening battery shows itself here first, as a slow turn or a rapid click.
Battery management systemBMS
The control unit that watches battery voltage, current and temperature and adjusts charging to suit. On a car fitted with one, a new battery normally has to be declared to it before the car will charge it correctly.
Intelligent battery sensorIBS
A small module clamped to the negative terminal that measures everything flowing in and out of the battery. The car uses its readings to decide how hard to charge and when to shed loads, so a loose or corroded sensor clamp produces faults that look exactly like a failing battery.
Earth strap
The heavy braided cable bonding the battery's negative terminal to the body and the engine. It carries the return path for every circuit in the car, so a corroded strap causes dim lights, slow cranking and warning messages that no new battery will fix.
Battery tray and hold-down
The moulded cradle the battery sits in and the clamp or bar that stops it moving. A battery left unsecured shakes its internal plates apart and can short against metal above it, so the hold-down is a safety part rather than a piece of trim.
Problems and symptoms
7What the car does when something is wrong, and the name a technician gives it.
Parasitic drain
Current the car keeps drawing after it is locked and asleep. A small amount is normal for the alarm and the control modules; a fault that keeps something awake will flatten a healthy battery in a few days, and the only way to find it is to measure the draw circuit by circuit.
Sulfation
The hardening of lead sulphate crystals on the plates of a battery left flat or undercharged. It permanently reduces capacity, which is why a battery that has been run completely flat rarely comes back to what it was.
Deep discharge
Running a starter battery far below the level it was designed for, usually by leaving lights on or a door ajar overnight. Starter batteries are built for short heavy bursts, not for being emptied, and every deep discharge takes a measurable bite out of what is left.
Slow crank
The laboured, drawn-out turning noise an engine makes when the battery no longer has the current to spin it properly. It is usually the first warning you get, and it tends to appear on the hottest morning of the week rather than a convenient one.
Auxiliary battery malfunction
A dashboard message specific to cars carrying a second battery, meaning the small battery rather than the main one has failed. It is easy to misread as a main battery fault, and replacing the wrong one changes nothing.
Terminal corrosion
The crusty white or blue-green deposit that builds up around the battery posts. It is an insulator, so it chokes the current path and produces symptoms that mimic a dead battery. It cleans off, but it also signals a leaking seal or an alternator overcharging.
Heat ageing
The loss of battery life caused by sustained high temperature, which accelerates the chemical reactions that wear the plates out. It is the reason a battery good for four or five years in a cool climate manages two to three in Dubai.
Service and diagnostics
6What a technician does to the car, and the words that appear on the job sheet.
Load test
A test that puts a real current draw on the battery and watches how far the voltage falls. It is the difference between knowing a battery is charged and knowing it is still capable; a resting voltage reading on its own tells you very little.
Battery registration
Telling the car's charging software that a new battery has been fitted, and what type it is. Skip it on a car that expects it and the charging profile stays tuned to the battery that was taken out, which shortens the life of the one that went in.
Jump start
Starting an engine using current from an outside source while the car's own battery is too flat to manage it. It gets the car moving; it does not repair or recharge anything, which is why the underlying cause still has to be found.
Learn more: Jump start serviceBooster packJump pack
A self-contained portable battery used to start a car without a second vehicle. It is what a roadside technician carries, because it works in a basement or a narrow street where parking two cars nose to nose is impossible.
Charging system test
A check of the alternator's output voltage and current, the drive belt and the wiring, rather than of the battery alone. It answers the question a battery test cannot: whether what you have is being refilled properly as you drive.
Memory saver
A small power source plugged in while the battery is disconnected, so the car keeps its radio codes, seat positions and learned settings. Without one, some cars need all of that set up again afterwards.
Roadside words
5The vocabulary of the tow truck and the fitment van, for the call you hope not to make.
Flatbed recovery
Moving a vehicle with all four wheels carried on the bed of the truck rather than rolling on the road. It is the only safe option for an all wheel drive car, a very low car, or one that cannot be steered or put into neutral.
Learn more: Car recovery in DubaiWinching
Dragging a vehicle onto a truck, or out of the position it is stuck in, with a powered cable. It is what makes a car recoverable when it cannot be driven or pushed, whether it is sitting in soft sand or at the bottom of a basement ramp.
Space saver spare
The narrow temporary wheel carried in place of a full size spare. It is lighter and smaller so it fits in the boot, and it carries a speed and distance limit printed on the wheel itself, because the car brakes and corners differently on it.
Learn more: Flat tyre changeRun-flat tyre
A tyre with sidewalls stiff enough to carry the car's weight for a limited distance after it loses all its air. Cars fitted with them often carry no spare at all, and changing one needs equipment built for the stiffer sidewall.
Learn more: Flat tyre repairCall-out
A visit to wherever the vehicle is, rather than the vehicle coming to a workshop. Some companies charge a fee for the journey on top of the work itself; at Battery Zone UAE there is no call-out fee and no charge for fitting.
Found the word, still unsure about the car?
Describe what it is doing and we will tell you which of these it is. The battery and charging test is free, there is no call-out fee, and we come to wherever the car is parked.