Possible battery issue

[allan1888]

I think I'll have to replace my battery soon, I got a warning message last week telling me that it was low. Took it for a long drive everything has been fine since, yet today my automatic boot was really slow to open and close but was fine with the engine running 

[Carlston]

47 minutes ago, allan1888 said:

I think I'll have to replace my battery soon, I got a warning message last week telling me that it was low. Took it for a long drive everything has been fine since, yet today my automatic boot was really slow to open and close but was fine with the engine running 

 

This is where it's best to have a voltmeter in your car. You can get them for under £2 each including shipping on ebay delivered from China. I've just ordered two different types, one has two USB ports with a digital voltage display, and the other just gives a digital voltage display without any other functionality. They both plug into the cigarette lighter socket.

 

Once you have a voltage meter fitted to your car, you can see what voltage your car battery is with the engine not running. Don't bother taking too much notice of the voltage with the engine running, as that will be around 14.4v and is a reflection of your alternator/charging system not your battery voltage. When the engine is not running, a good battery will have up to 12.8v when there isn't much battery drain, eg. headlights and heated rear window turned off.

 

If the voltage of your car battery quickly drops to below 12.6v within 24 hours of running your car engine, then that could indicate a bad battery. What happens with a car battery that goes bad, is that one of the six cells fails first. So although you will probably have five good cells, a car battery is only good if all six cells are good. Your 12v car battery is actually made up of six 2v cells connected in series. Hence 6 x 2v = 12v. In fact, when fully charged each cell will be just over 2.1v, so the 2v figure is really just a nominal value.

Edited 19 March, 2020 by Carlston

[KenONeill]

As above, but you can get a digital voltmeter in a local shop for sick squid, so why wait for the Chinese?

[themanwithnoaim]

Shouldn't worry, I don't think anybody will be doing to many miles driving for a few weeks

[allan1888]

just remembered i had a battery tester in my van. just checked the car and the battery is currently at 12v bang on, so looking like it may be on the way out. ill take it on a decent run tomorrow as its done a fair few really short journeys recently and if it doesn't improve ill replace the battery