Update: multimeter readings!

Hi group,

Ok I got my multimeter today cheapy from maplins. connected it all up after reaidng the instructions. here are my readings.

Battery test while car was off: 12.9v

alternator test: with heater on full, lights on etc and I got 13.9v

As I was passing a halfords today I dropped in for a free battery test just to listen to what they think. Guy came out with his multimeter and a battery tester, and got the same readings as me and told me the battery should be reading a minimum of 13v even though it s a 12.4 circuit which was his exact words and said that it would need changing soon. What do you think ?

He said that nothing looked to be wrong with the alternator from his reading, so it would be best to buy a new battery in a few months as this one is on its way out. He said not to rush in buying one but as I didn't have a history of the battery it would be advisable to be safer than sorry, he did say the halfords range are very good and for my car it would be £53 he said though any varta or boosch battery is ideal for vw cars.

thats pretty much all. I look forward to your views and advice.

Thanks

Reply to
tishtash
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Leave the car overnight, then test the voltage before starting it.

If it's more than about 12.5V, it's fine.

Chris

Reply to
Chris Whelan

He's full of shit.

I just paid £42 for a Bosch battery, 3yr guarantee, with enough capacity for a diesel transit van.

Reply to
Conor

Conor ( snipped-for-privacy@gmail.com) gurgled happily, sounding much like they were saying :

Reply to
Adrian

Looks fine though as someone else said test it after leaving it over night.

Take it with a pinch of salt.

Reply to
malc

Voltage readings mean very little except as a very rough guide to the state of charge. He should have had a proper battery tester that puts a very high but brief load on the battery and analyses the results.

Reply to
Dave Plowman (News)

What Dave said about testing under load. I recently bought a Bosch battery for my Golf (MK2, 1.8, I'd guess it's harder work to start that most Polos out there) - £30 ish from GSF, about £3 more than a yumcha brand, and about

120CCA stronger IIRC. CCA is Cold Cranking Amps, the amount of current the battery is capable of putting out to start the car, and more is better.
Reply to
Doki

With the greatest of respect, I beg to differ on three counts.

If a battery has one weak cell, but is otherwise sound it may continue to start the car for some considerable time. If you are running an old car into the ground, that might be all you want. Using a high-discharge tester on such a battery will usually kill it stone dead.

Testing battery voltages, if done appropriately and analysed sensibly, will often tell all you need to know. In addition, you will learn if the charging circuit regulation has failed in a way that causes the battery to be over-charged. No amount of discharge testing can do that.

Finally, if you want more than a rough guide to the state of charge, you need to use a hydrometer and thermometer - not always possible on modern batteries of course.

Chris

Reply to
Chris Whelan

Two things. The old fashioned high discharge tester takes no more current than can the starter, so if it kills the battery, so will the starter. Modern ones (which my local Halfords use) look rather similar to a multimeter and put a short duration high load on the battery under microprocessor control and analyse the results. They can therefore give a readout of the battery parameters without the need for human interpretation - no bad thing when you're talking some Halfords 'technicians' as the OP's anecdote amply demonstrates.

Sensibly being the operative word. But this requires knowledge. For a start, there's no point in testing the off load voltage immediately on a battery that's been on charge - it must be left to 'settle' for several hours.

Indeed - however that wasn't the point I was answering. The Halfords bloke was talking about battery voltage.

All you need these days is a decent battery tester. They're not cheap, though. But you should find them in any decent place that sells batteries. Finding an operative that doesn't lie about the readings might be more difficult.

Reply to
Dave Plowman (News)

My battery is crying for a change, been meaning to get round to changing it. I've always seen bosch as a good brand where did you find the £42 one from ?

Reply to
johnbond

Local motor factor.

Reply to
Conor

Never trust a car parts salesman.

What are the symptoms for all this mucking around that you are doing?

Reply to
Soggy matches

e.g. watch the reading whilst somebody starts the engine. 12.4V is fine, but tells you nothing about the batterys ability to start the car.

Reply to
Duncan Wood

My car was a little sluggish when starting in the mornings so thought I'd see if it was a battery \ alternator problem. And its a new skill I've learned thans to the folks in here which I owe them a drink for :)

Reply to
tishtash

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