What are the tell-tale signs of a failing battery? It would be very useful to know, especially as I have started driving to Malaysia again.
The first bit of information you must have is the age of the battery. Most of them have some form of marking identifying the date of installation in the car. Generally, lead-acid car batteries will last about three years. Hence, you need not be vigilant till it is more than two years old.
Some batteries come with an indicator that turns from black to red or yellow when the battery condition falls below a certain level.
The first sign of a failing battery is always slow engine cranking when starting. More current is drawn from a 12-volt battery by the starter motor than any other electrical component, except on hybrids with lithium-ion-powered starter-generators.
There is no way to predict how much longer it will last from the first sign of lethargic cranking, so you should have the battery checked when you detect this symptom.
A competent battery shop will not only check the state of the battery, but also the alternator's performance. Battery voltage should increase slightly when the engine is revved above 1,500rpm to read no less than 14 volts -even though the battery is specified as a 12-volt unit.
Other signs of a failing battery include inconsistent brightness from any of the vehicle's bulbs - including interior lights - during idling. Headlamps, in particular, will be easy to notice. However, this will not be noticeable if the lamps are xenon or LED ones.
On cars with electric power steering, a weak battery will often cause the steering wheel to feel tighter or heavier, especially during fast left-right manoeuvres.
When replacing a battery, you must find out if your car has a type of battery-management system which requires an update of the engine-control unit with a new battery code. This is necessary on some cars to refresh the alternator's charging pattern and can be performed only with specialist equipment.