Battery problems

[Deleted User]

Tried to start car the other day - battery flat.

Called AA who came out and got it started. They checked it all and said, battery fine, and its charging well. So I assumed I'd left the lights on or something.

Today, flat again. Definitely not left anything on this time.

So, is it:-

1. Faulty battery after all.
2. Something draining the battery somehow.

adouglasmhor

If your battery is being charged at the right voltage it's a faulty battery.
If it's not it's an electrical fault, wiring, alternator or something you don't see draining the battery.

Foxy-Stoat_3

What car is it? How old is the battery?

Very low temperatures kill weak batteries.

You could try disconnecting the negative terminal and see if its dead the next day. If your car has a boot light, see if it stays on with the boot shut.

AdrianC

Get a multimeter. £10-15, and they're always useful.

Start the car, meter onto 20v DC range, and check you've got 14-14/5v at the battery. If not, it's not charging properly.

Switch the car off, take the -ve battery lead off, meter onto 1A range, and check the current flowing between -ve lead and terminal. Wait a minute or two, reset the alarm if necessary, and see what's being consumed. If it's more than about 0.1A, something's flattening the battery.

If they're both OK, the battery's probably knackered.

WTFH

Since the AA came out, have you done any long journeys?
Do you do lots of short journeys with the heat up to full, the rear window on, heated seats on?

fivetide

I'd go for a combo of Foxy and WTFH's advice in the first instance. Make sure there are no courtesy lights staying on anywhere.

Also, did you go for a good drive to re-charge the battery? How long ago is "the other day"? A day? Two? A week? If you didn't give it a good charge in the first place and have left it stood again that might well be the issue.

Mind, a lot of batteries don't like to be flattened and can struggle to recover (barring leisure batteries which are designed with this in mind)

cootuk

Boot or glovebox courtesy lights on?

Joe_Horner

Also check the battery connections. The earth lead on my Pug will randomly give a poor contact where it connects inside the terminal clamp, which appears as a flat battery.

It's a pig to replace cos it's attched to the body right down the back of the engine, so I give it a wriggle when it won't start and goes again every time. Really must get around to a more permanent fix....

Strider590

Last week my battery was draining over night, it'd go from 12.8v after parking up, to 12.5 by the morning. I just replaced it and no more problems. The new one stays at 12.9 all night and all day.

EdGasket

...you mean 'All Day and All of The Night' ...though I don't think the Kinks were talking about batteries

[Deleted User]

Foxy-Stoat wrote: »

What car is it? How old is the battery?

Very low temperatures kill weak batteries.

You could try disconnecting the negative terminal and see if its dead the next day. If your car has a boot light, see if it stays on with the boot shut.

Merc A170 2001. Battery less than year old.