Hi Paul, thank you for your informative articles. I am a fairly new driver of a Mercedes Benz. I have recently had car starting difficulties. At some points I have had to jump start my car. My neighbour suggests I need a new battery. But how do I know whether the current battery is spoilt because it looks new. Please advise. Margaret Kamya
Hello Margaret, a battery is not an ‘electricity tank’, rather it is a chemical reaction in a plastic box designed to produce electricity when charged. There are warning signs we can use to identify a failing battery:
Slow engine crank or rapid clicking sounds when you attempt to start.
Poor malfunctioning electrical components which require battery power such as window screens, remote central locking or the clock.Constant display of the battery warning light. This suggests there is a problem with the battery or its charging system (alternator).
Physical signs of failure such as a swollen battery case due to overcharge or reaction to extreme hot or cold conditions, broken terminals, dirty terminals, cracks or holes in the battery. Also observe the wet battery acid levels which should be the same in all cells and at the recommended maximum level.
Old age can also be a warning sign of impending battery failure. The average lifespan of a battery should be about four years. However this fluctuates with charging time determined by how far you often drive or the number of complete discharge cycles. So for some wet acid batteries regularly driven for short distances, one year is their average lifespan.
A sure way to determine if a battery has failed is to test it. This can be done by yourself (with the right tools or know how), a mechanic or qualified battery technician.
Common tests include measuring the cold cranking amps using a battery tester or voltmeter. This is also useful when carrying out a load test in a workshop environment.
Using a fully charged battery an attempt to crank while monitoring how fast voltage drops. Professional battery technicians use a hygroscopy tester to assess battery acid concentration levels.
In my more 20 years’ experience fixing cars, I have established that the biggest cause of battery failure is driving habits. Batteries on cars that are regularly driven for short distances suffer from low charge (not charged enough).
Failure to maintain acid battery water levels is another factor. This is where the maintenance free gel batteries seem to offer an ideal alternative.However this does not negate or solve the low charge factor.