Dead Battery

[Joe M 0]

Went out to the car today and the remote for the alarm wasnt workng, had a look inside and the clocks were blank. :mad:

Pretty sure its the battery as its been dry before and I topped it up and ive noticed the car turning over slower on the starter the last few days.

So, whats the recommended battery, will a cheap one from a motor factors do or should I be trying to get a better one, also, what rating should I get?

 

Finally, once ive got the battery in, how do I check the alternator? Is it as simple as putting a multimeter across the terminals of the battery with engine running and making sure it reads higher than 12v?

[dazzyvr6 0]

i bought a bosch silver top one for mine about 2 years ago,quite expensive though,but most batterys come with life time guarantees now

[Supercharged 2]

Yes the Bosch ones are very good and OE i think - GSF sell these very cheap now as well - 4 year warranty i think

 

I don't think most do come with lifetime, you can get them but there obviously more expensive.

 

The previous owner put a Halfords one in mine, I thought these were equivelent in quality to the Bosch ones but have heard alot of bad things about them latley - anyone else had probs?

[Henny 0]

Try a Varta battery. The make some of the best batteries in the world and aren't very expensive... My mate's garage now fits these as standard instead of the Bosch silvers that he used to fit... 8)

[Andi 2,147,483,647]

Finally, once ive got the battery in, how do I check the alternator? Is it as simple as putting a multimeter across the terminals of the battery with engine running and making sure it reads higher than 12v?

 

When the engine isn't running, your battery should read just over 12volts. With the engine running, you should be getting at least 13.4volts with a voltmeter accross the terminals.

[dr_mat 0]

The alternator on my VR6 puts 14.2v out. That's what you should see across the battery with the engine running.

Dunno if mine is unusual or something (maybe someone fitted a heavy duty 'nator), but it's a 90A 14.2V Bosch. Looks like it's been replaced (I have a receipt for it somewhere) since the car left the factory, but don't have reason to believe it's any different from the default model.

Fully checking the alternator really means checking that it can continue to deliver 14.2V under extreme current conditions, so maybe stick all the lights on and the screen heaters and everything (and get the engine cooling fan to come on - that's a huge load), and see if it can still keep the output steady at the rated voltage.

[Joe M 0]

Ok, new battery fitted, tests with multimeter done.

Started off fine, just over 14v on the reading.

Switched a few things on, dropped to about 13.6.

I then let the engine warm up fully.

Everything on this time, seats, fans, lights, fogs and rear demister, the reading dropped quite a bit to 10.something, I then switched everything back off and looked at the multimeter and it was at about 8 :x .

I switched the engine off and started it again and the reading was back up to high 13's.

 

This suggests to me its the regulator on the alternator (hopefully) as the alternator can provide enough juice when it wants to but isnt under heavy load. Does this sound right?

 

dr_mat, My alternator is the 90A as well, but I think it was Valeo, will double check as im now off to perform an ecu reset and check the readings again.

[dr_mat 0]

Sorry, that's beyond my knowledge at this point... :?

I'll leave the discussion of that stuff to someone more familiar with car electrics than I.

 

I'd be pretty confident your battery was duff if the voltage dropped to 8V even when the load was removed. However, it could be that the alternator has simply never pushed enough charge into the battery to keep it up there.

To test the battery is simple: get a charger, charge it overnight and then keep checking it for the next few days. Even if the alternator is completely screwed, you should get a few minutes starter use out of the battery (not all in one go, you'll melt something!!!), and certainly the battery's voltage shouldn't drop significantly when you're not using any of the electrics.

[Kevin Bacon 5]

Sounds like the alternator needs attention. Unfortunately the factory fit Bosch ones don't simply take a diode and brush pack, it needs removing from the car and rebuilding. I had a word with my local auto electricians about it and they said you'd be better off fitting a new one.

 

You should be getting 13.5+ with everything switched on. The engine might slow down a bit as the alternator puts more load on the engine but it should maintain that voltage.

 

As for batteries. Vauxhall ones are the best because they're made my AC Delco, a very highly regarded battery producer and sealed for life. You even getting a little indicator showing battery health. Green for good, yellow/orange for dead/dying.

 

Kev

[Kevin Bacon 5]

Sounds like the alternator needs attention. Unfortunately the factory fit Bosch ones don't simply take a diode and brush pack, it needs removing from the car and rebuilding. I had a word with my local auto electricians about it and they said you'd be better off fitting a new one.

 

You should be getting 13.5+ with everything switched on. The engine might slow down a bit as the alternator puts more load on the engine but it should maintain that voltage.

 

As for batteries. Vauxhall ones are the best because they're made my AC Delco, a very highly regarded battery producer and sealed for life. You even getting a little indicator showing battery health. Green for good, yellow/orange for dead/dying.

 

Kev