Car Battery Faults
photo credit: Charles Williams
OK,so your car won’t start. The engine won’t turn over so you decide it’s a flat battery to blame. If you forgot to switch off your lights and they flattened the battery, then it’s just a matter of hooking up the car battery charger to bring the battery back to life. But what if you don’t know the reason for the flat battery?
Causes Of A Dead Car Battery
Usually the cause of a dead car battery (with no obvious reason such as lights being left on) is either a faulty battery or the battery is not being charged by the alternator. This could be because the alternator (the component which charges the battery) is faulty, or it could be because the belt which drives the alternator is slipping.
A quick way to check if the alternator is actually charging the battery is to start the car when it’s dark and switch on the headlights. Let the engine tick over at idle speed and look at where the headlights are shining. If the alternator is charging the battery OK, the lights should get brighter when you press on the accelerator and increase the revs. If the brightness doesn’t change, then it’s likely that the alternator isn’t charging the battery.
If the car battery is faulty, then it could be that it has just reached the end of its life. Batteries will usually last for between 3 and 5 years, depending on how fully they are charged. If you only do short trips in the car, the battery is going to spend most of its life at below full charge, and this will mean that the battery does not last as long as it would if you were doing longer trips and it was charging fully. If you have a multimeter (voltmeter) you can check the battery voltage with it. Touch the red multimeter lead to the positive battery terminal and the black lead to the negative battery terminal. With the engine off, the voltage should be between 12.5 and 12.8 volts. Start the engine, and when it is at idle speed the voltage should increase to between 13.6 and 14.3 volts. If the voltage does not increase, the alternator may be faulty.
If you are having starting problems, it could be due to loose battery terminal connections. Check that the red and black leads are tightly connected to the battery terminals. Another possible cause of starting problems is corrosion between the battery connections and terminals. If this is the case, they will need to be disconnected and cleaned. Make sure that the engine is off before you disconnect the battery.
