The clearest sign of a failing car battery is slow cranking: the engine turns over lazily before it starts. Others are a battery or charging warning lamp, start-stop that no longer switches the engine off, electrics that dim or reset on start-up, a swollen case and heavy corrosion on the terminals. In hot climates a battery can also fail with almost no warning.
What does a slow crank tell you?
Starting the engine is the hardest job a battery does, so it is where weakness shows first. A healthy battery spins the engine briskly. A tired one makes the starter sound slower and heavier, often worst on the first start of the day. AAA names slow cranking as one of the two main signs that a battery is close to failing.
Take it seriously the first week you notice it. In a cool country a slow crank can go on for months. Here a battery that is cranking slowly in the afternoon heat has little reserve left, and the next step is often a rapid clicking sound and no start at all.
Why has start-stop stopped working?
On a start-stop car this is frequently the earliest clue. The car only switches its engine off at a junction when the battery management system is confident the battery can restart it. As the battery weakens, the system quietly stops using start-stop to protect itself, long before you notice any slow cranking.
It is not proof by itself. Start-stop also stays off when the cabin is still cooling down, which in an Abu Dhabi summer is most of a short journey, and Varta notes that a new battery which was never registered can restrict the function too. If it has not worked for weeks in mild weather, have the battery tested.
Which warning lights and electrical faults point to the battery?
The battery-shaped lamp on the dashboard means the charging system has a problem, which may be the battery, the alternator or the wiring between them. AAA lists that lamp alongside slow cranking. Modern cars also show text warnings such as low battery or battery discharging, and may shut down comfort features to save power.
- Battery or charging lamp on, or a low-battery message.
- Screen, clock or seat memory resetting when you start the car.
- Interior lights or headlights dimming as the starter turns.
- Central locking or power windows noticeably slower than usual.
- Several unrelated warning lights appearing together at start-up.
What does a swollen or leaking battery mean?
A battery case should have flat sides. Bulging sides or a raised top mean the battery has overheated or been overcharged, and it is finished regardless of how the car starts. A smell of rotten eggs, wet patches on the case or acid tracks on the tray point the same way.
Treat it as a safety matter. Do not jump-start a swollen, cracked or leaking battery and do not lean over it. Keep sparks and cigarettes away, avoid touching any liquid, and have it replaced. Ask for the charging system to be tested at the same time, since overcharging may be what caused it.
Do corroded terminals mean the battery is failing?
Not always. White, green or blue crust on the terminals adds resistance, so a good battery can behave like a weak one. Cleaning and tightening the clamps sometimes cures a slow crank completely. Heavy corrosion that returns quickly, though, suggests the battery is venting acid vapour, which is a sign of age or overcharging.
Check the hold-down clamp while you are there, because it matters more than most drivers think. AAA warns that missing or loose hold-down hardware can significantly shorten battery life because vibration breaks down the parts inside. A battery you can rock by hand needs securing.
Can a battery fail without any warning?
Yes, and in this climate it happens often. Heat ages a battery from the inside while warm weather makes the engine easy to start, so the battery copes right up to the day it does not. A car that started normally in the morning can refuse after an hour in a mall car park.
Age is therefore a sign in its own right. Consumer Reports recommends a yearly load test once a battery is two years old in a warmer climate. A test takes a few minutes and tells you how much capacity is left, which the dashboard never will.
What should you do when you notice these signs?
Get a test before you buy anything. A proper test checks the battery under load and the charging system with the engine running, so you find out whether the battery, the alternator or a loose connection is at fault. Our technicians carry out that test at your parking bay on Yas Island and show you the result.
