Need a new battery?

[sebmaster]

Hi,

The other day I went to start my car after it had been left for some time (couple of weeks) and it needed a jump start. Few days after that I started it on a cold morning fine but then it ended up stalling at a roundabout and it took me about 120 seconds to get it going again.

Ive noticed when idling that sometimes the rev counter drops very sharply (after the roundabout incident I now rev it a bit so it hasnt stalled).

Whenever I start the car the voltmeter on the dash drops to about 8v until the engine starts and from what I read online all of this says I need a new battery, but the car has only failed to start right off twice since Ive had it, if the battery really was dead surely id need a jump start practically every morning?

Do you think its worth getting the battery replaced and see what that does or could this be another fault?

[delta925]

Go to an autoelectrician with a professional battery tester that can determine if the battery is faulty or just flat and needs charging.

When I had trouble a few years ago I went to LSUK where I bought my battery.
They confirmed it was faulty and replaced under 4 year warranty without a quibble.

[sebmaster]

Hi, Thanks Delta.

I took it to Quickfit and asked them to check it. I was a little wary of taking it to a place like that and asking what amounts to "do you think I should buy a new battery off you?" ;) but they were very good and the guy didnt even charge me anything.

They said that the alternator was putting out around 13.8v at the lowest end of the spec but it wasnt anything to worry about now.

Has anyone else noticed their cars revs dropping when idling, I know that after a while the engine idles more slowly anyway, trouble is whenever it does drop its always with loads of cars behind so im not keen on leaving it to see if it stalls again or not.

[delta925]

Hi, You were lucky with that branch of Kwik-Fit.
Yes 13.8V low for alternator measured across the battery with nothing switched on, usually over 14V so possibly one bank of diodes has failed - but did they test the battery?

Engine revs will drop / engine labour at idle if a load cuts in.
Switch on heated rear window for example and note the effect.

Modern batteries can fail suddenly too - fine one day will not start the car or hold charge the next.

[JIGGY C]

Just a bit of infor for those using this thread - I too stored my car for six weeks and when i got her back on the road the battery was dead - once jumped I have exactly the same problem, the dreaded low revs!! I am going to change my battery and will update the thread as to the result to hopefully help you in the future.

[sebmaster]

Hi JIGGY C,

Just to let you know what happened since my first post.

When I took my car in for the MOT my local garage found the temperature sensor had gone, which was the result of the low revs, this was replaced and that fixed the problem.

The battery problem remained however and the car continued to need jump starting. Eventually I replaced the battery with a slightly larger one (well if im going to replace it I might aswell get a nicer one ;)) which just about fitted; since then no problems with it not starting.

When you replace the battery chances are you'll encounter the fluctuating idling speeds, I got this every time I jump started, half the time it would disappear after leaving the car off for a few minutes however if it doesn't you'll need to do a throttle body alignment with VAG-COM:
http://www.ross-tech.com/vag-com/cars/throttlebody.html
(I'm allowed to post that right?)

You'll need the software and a cable from eBay - sounds like alot for just replacing the battery but believe me even if you only use it once or twice a year the one off is definately worth it, its a really useful bit of kit especially as my local garage doesnt have a VAG reader/adapter whatever.

Good luck, hope your car is ok.