Battery dead after MOT

KatieDee

We have an excellent garage near us, which I chose to have my MOT done at. Due to illness, the mechanic wasn't able to look at my car until late last night, and dropped it off after midnight. Not really relevant, but my banged up clanger sailed through Its MOT. 

I came to start it this morning and the car was completely dead. I can only assume something was left on, which has drained the battery. Not a big problem, the mechanic came out immediately and jump started me, which allowed me to get into work, on this lovely Monday morning!

I drove over one hour to work, a mixture of motorway and standard roads. When I arrived, I turned my engine off and just tried it again, to make sure everything was okay. Absolutely dead again.

I appreciate this was probably a mistake but is it likely my battery will need replacing now? I'm anxious because I can't leave my car running (I work in the city) and I can't guarantee my break down service will able to get to me before I leave for work at 4pm. 

Just trying to work out the best course of action! 

Farway

How old is the battery?

KatieDee

Farway said:

How old is the battery?

It's a few years old now, I think maybe 3 years or so?

It isn't really new though, and I do a lot of rubbish driving (stop start, inner city traffic) although I've not really had any issues before today. Think being left on for whatever reason may have been the final straw! 

AdrianC

First, make sure it really is the battery.

Do you have a multimeter? They're cheap and widely available. Check the battery voltage with the car turned off (you should see 12-12.5v), then check it with the engine running (you should see 14-14.5v).

When you turned the key, you said it was "completely dead" - as in none of the dash lights came on, nothing at all happened? That'd be a very, VERY flat battery - not just "Oh, c'mon, start...", but utterly pancake. Regardless of age, that's not going to do a battery any good at all - and takes a long time of significant current consumption.

Do any of your colleagues park near you, and do any of them have a set of jump leads in their boot (again, cheap and widely available)?

KatieDee

AdrianC said:

First, make sure it really is the battery.

Do you have a multimeter? They're cheap and widely available. Check the battery voltage with the car turned off (you should see 12-12.5v), then check it with the engine running (you should see 14-14.5v).

When you turned the key, you said it was "completely dead" - as in none of the dash lights came on, nothing at all happened? That'd be a very, VERY flat battery - not just "Oh, c'mon, start...", but utterly pancake. Regardless of age, that's not going to do a battery any good at all - and takes a long time of significant current consumption.

Do any of your colleagues park near you, and do any of them have a set of jump leads in their boot (again, cheap and widely available)?

My lovely colleague is going to jump start me when it's time to go home, and I've spoken to the garage (who I'm waiting for a call back from now).

I know this isn't very technical but when I turn the key, it doesn't go "ch-ch-ch-ch-ch" like it's trying it's hardest to tick over. There is a clunk and then nothing. 

castle96

Is there a tick-tick-tick? Could then? be the starter motor

AdrianC

KatieDee said:

I know this isn't very technical but when I turn the key, it doesn't go "ch-ch-ch-ch-ch" like it's trying it's hardest to tick over. There is a clunk and then nothing. 

But all the dash lights come on as normal?

So there's something in the battery - just not enough to turn the starter.

KatieDee

AdrianC said:

KatieDee said:

I know this isn't very technical but when I turn the key, it doesn't go "ch-ch-ch-ch-ch" like it's trying it's hardest to tick over. There is a clunk and then nothing. 

But all the dash lights come on as normal?

So there's something in the battery - just not enough to turn the starter.

They don't come on and stay on - they all flash on for less than a second, then if I keep turning the key, one light flashes on and off (the seat belt one) and the rest of the dash is just dark.

It's a Mini Cooper if that helps. 

Goudy

Modern cars don't even attempt to turn the starter motor if the battery is flat or under charged, they usually do nothing but blink a dash light or two.
If there's too little power in the battery it won't activate the relay for the starter motor, so the starter motor won't turn at all. No slow whir, whir, whir like cars of yesteryear.

You either have a duff battery, a duff alternator or a parasitic drain somewhere that's flattening the battery.
As it jump starts I would suspect the starter motor is ok.

As Adrian suggests a few quick tests with a basic voltmeter can usually determine what the problem is.
Ask your garage to to perform the three checks above for you.

Ectophile

Sometimes batteries do suddenly fail.  No amount of recharging will fix them.  If you are lucky, they work enough to operate the ignition and get the car going with a jump start or a bump start.

When that happens, your only option is a new battery.