My battery was flat on the Golf when I got back from a 4 day break recently. Same battery from new so I jump started and went and bought a new Bosch Silver and fitted - all fine since. However I recently invested in a cheap multimeter and am now in the position that a little knowledge is a dangerous thing.
When I check the car battery in the morning after an overnight stand it reads 12.1 V or thereabouts, with car running after a few mins levels out at 13.9V.
A little bit of reading on the web tells me a fully charged battery should read more than 12.1 V and I should be getting over 14V with the alternator running. Is this true?
I suppose my questions are: are these numbers acceptable? Is the alternator on its way out? Could there be a current drain?
Wish I'd never bought the multimeter now!
All help gratefuly received.
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I'd wonder about the accuracy of your meter. If the battery was resting at 12.1 volts with no load, then I doubt it would have started.
After 2 hours of no current flow in or out: 12.6 and above - fully charged; 12.4 half charged; below 12.2 flat; 11 and below, faulty.
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...had not thought of that, so went out to check the smax - 12.4V there, perhaps is not entirely accurate then.
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What does the Smax read immediately after starting - 15.4v?
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Just checked 13.8V (almost same as Golf...) I'm confused. Both cars are now running and starting fine!
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I think you need to compare it to another meter - a Fluke would be good.
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...Guess a £7 B&Q meter is £7 for a reason!
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