The big question everyone has when they switch on their car to find that the battery is flat is:  what could have caused it? People find it hard to understand how their car battery could suddenly have become flat when it had been working perfectly the day before.  Besides the immediate inconvenience, there also lurks the possibility of having to cough up more money for a new car battery.

Probe provides some tips that can help you avoid this potential problem.  So before panicking or driving kilometres to the next dealership to have your battery checked, take a read-through below.

The 4 big no-nos

There are four main causes that will cause your battery to go flat:

leaving the lights on, leaving the radio on while the engine charging system is off, having the car stand without running for an extended period of time, or electrical faults of the car itself.

If you leave your lights on for an extended period of time, this will definitely drain your battery.  

Playing the radio while the engine is off has potential to drain the battery, especially if you do this repeatedly or over an extended period of time. Car radios simply can kill your battery – so don’t use your car radio as the party music system otherwise you will be knocking at the dealership door for a new battery sooner than you think.

A car that is stationary for long periods of time will experience a flat battery due to sulphation (which we wrote about in detail here).  Sulphation is caused by long standing times so it is always recommended that the car be driven around periodically to ensure that the sulphates are continuously being broken down.

You can test yourself whether battery drainage is due to any of the above three battery draining possibilities, by taking the battery out of the car and charging it using the supplier’s specifications.  It is also an idea to check that the battery contact cables are not loose as this will also drain the battery.

The instrument used to test the voltage in a battery is a voltmeter. You could borrow one from a neighbour or purchase one from any hardware shop.

If you suspect that it might be none of the above three reasons and might be due to an electrical fault, you could take the following steps before going to see a qualified auto electrician: charge the battery off the car to full capacity according to suppliers’ specification and then re-install it. After re-installation, check the voltage of the battery and then check later, perhaps at the end of the day, to see if the voltage is dropping.  

It is important to ascertain if the voltage is dropping because this could mean your charging system is not putting back enough charge and there could be an electrical fault somewhere.  The problem here is that a continuously draining battery will eventually kill it due to the deep discharges and you won’t be able to charge the battery to full capacity.  This type of fault is not an honoured warranty claim hence you stand to lose your chance of getting a replacement warranty if you delay taking action.

What to look for when checking voltage

If there is no electrical problem or fault and the charging system is 100 % and the contact cables are working, the fully-charged battery should give around 12.6 V.  The battery will not drop if the car charging system is working and there is no electrical fault. The car system maintains the voltage in the battery.

After driving the car with the assumption that everything is okay, there shouldn’t be a significant drop in voltage since the charging system will be working.

At the end of the day if one were test their car and the voltage shows at least 12 to 12.6 V there shouldn’t be anything to worry about.   Voltage should preferably be around 12.4 volts.

However, if one tests the battery and realises that it has dropped just below 12 volts but had given an initial ready when fully charged of around 12.6 volts then, there is a problem. In this case the car is drawing more out than what is being put back or the charging system is faulty. If this case arises one has to see an auto electrician quickly before the battery is damaged further.

A visit to the ‘car’ doctor

If your voltage is dropping you will need to see a qualified auto electrician to thoroughly check your vehicle to investigate why the battery continues to drain while the engine is off.   In this instance, the charging system must be checked and confirmed as being okay, and any potential faults should be tested.

At Probe, we’re always here to help.