The main symptoms of a dead battery
To assess the signs of a battery on the verge of draining, use a voltmeter to measure the voltage at the terminals. The “minus” must be detached from the car in this situation. 12.4 V and above is normal; 12.4-12 V indicates a little discharge; the car will start, but you must drive longer or charge the battery.
Up to 11 V – the engine, particularly a diesel engine, will not start; charge it immediately. Worse, if the voltage at the terminals is 10-10.5 V, this is very certainly a 100% short circuit in one of the cans, and only a replacement.
Why is it important to test your car battery?
You don’t want to rely on guesswork when it comes to knowing how much life is left in your battery. If you’re super organised and know when it was last changed and how much driving you’ve done with it, then that’s a fantastic start.
But the only way of predicting how much longer your battery will last is by testing it. That’s where the team at Roskill Auto Mechanical can help.
If you don’t test your car battery, you may face an unwanted scenario, such as:
- Your car won’t start (and you know it always happens when you’re in a hurry or late for work)
- Your car may stall (possibly in a remote or unsafe place)
How long do car batteries last?
The life of a car battery depends on factors such as:
- how much you drive
- the type of driving you do
- how much you use the battery without actually driving
- whether there are extreme weather temperatures where you live
- whether you leave your car sitting without driving it for long periods of time
On the whole, car batteries can start to wear down in as little as three years. If your car battery is between four and five years old, it may be time to replace it. Batteries don’t often last much longer than five years, so if you’re driving around with a battery this old, you may find yourself stalled and stranded.
Car battery voltage test
A simple way of checking your battery’s voltage involves using either a voltmeter or a multimeter. These are small hand-held instruments that are similar in some ways, but they’re not quite the same.
A voltmeter measures the electrical potential difference between two points in an electric circuit (its voltage). A multimeter does more – it is a multi-purpose measuring device which can directly measure various electrical quantities such as voltage, current and resistance.
If you’re just testing the voltage of your car battery, either of these devices will do.
A fully charged battery will measure about 12.6 volts when the car is not running (its resting voltage). When the car is running, a fully charged battery will rise to somewhere between 13.5 and 14.5 volts.
Car battery drain test
If you suspect something is draining your battery, this is a test we can do to determine the culprit. Some mechanics refer to it as a parasitic drain test – because there is a “parasite” that is draining your battery. It’s not an actual parasite, of course. It’s something that is causing your battery to run down when it shouldn’t.
Things that may be draining your battery might include a faulty headlight, alternator, or other rogue electrical part.
Testing for what is draining a car battery involves investigating the fuse panel(s) in your vehicle and checking its electrical components. It’s best to leave this work to the trained and experienced mechanics.