Car battery suddenly died.

[earthman]

The question is it holding its charge? Plenty of batteries show 12V, But when under load they don't have the power to turn the engine over!

14 point what volts ? It does matter what voltage a battery gets, for example 14.2v won't be enough.

Yes 14+ volts proves the alternator is working but unless it outputs enough voltage it won't charge the battery properly.


Exactly, I replaced a pair of batteries on a little fishing boat the other day, the engine start battery showed 12.5v but when I put the drop tester on it the voltage rapidly went south to 2.7 volts and as for the domestic battery well that did well to manage 3 volts with no load on it, mind you there was a chunk missing from the corner and the acid was below the plates on the other 5 cells, I was amazed it managed to generate any voltage at all given the state of it.
The scary thing was that whoever had refit the domestic battery had connected some of the red leads to the negative terminal and some of the black leads to the positive terminal

Well she's had no further problems using the car since so yes, certainly the battery were at fault I'd say.

I did try and get the old battery drop tested at the likes of an Halfrauds service centre but they were rammed with customers.

 

[merryman]

14 point what volts ? It does matter what voltage a battery gets, for example 14.2v won't be enough.

Why not? I check charging systems and fit new batteries regularly, and depending on the state of charge, anything over 14v is fine, in fact quite a lot are charging fine when cutting out at 13.5v. The regulator cuts the charge to suit the battery and demand on it.

 

[Farside]

When cars had dynamos the batteries seemed to fail gradually and give notice. The sudden death syndrome seemed to coincide with the introduction of alternators.

Also co-incided with the battery makers moving to thinner plates and just enough material to last, especially at the budget end. A good quality battery still had better stuff in it.