Alternator/Battery gurus help please :)

-Mike-

-Mike-

-Mike-

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I'm hoping someone can help me with this -

Just wondering if you can tell me whether my diagnosis is correct/incorrect.

Battery voltage with car left overnight between 12.01 and 12.10 = Duff battery

Resistance between alternator casing and battery negative is almost 0 = earthing between the two is ok

Car voltage with engine running all ancilleries off 14.04

Car voltage with engine running, headlamps, heater, rear demister on 13.65 .......... Alternator in reasonably good health?



Thanks :)
 
static voltage of 12v could mean it's just flat.

1. Have you charged it overnight off the vehicle.

2. Have you done a discharge or drop test on it. (readings should stabilise above 9v under load)

3. Have you checked the resistance between the "nut" on the back of the alternator and the positive terminal of the battery.
 
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GeX said:
What is the problem?

12v is fine for a battery when the engine isn't running.
Click to expand...


Not when you are using open circuit voltage to second guess the battery condition
12v is about 25% charge.
But it's a crap test anyway, hence why I said what I said in my OP.

There's been no mention of the actual problem yet.. hint ;-)
 
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Under cranking the battery voltage drops to 7.52v according to vagcom and pretty much the same with a multimeter.

Code: 
Voltage        
12.01
7.52        <<<CRANK>>>
8.51
10.18
11.1
12.46
12.69
12.69
12.69
12.84
12.84
12.92
13.15
13.15
13.22
13.38
13.3
13.45
13.76
13.76
13.91
13.98
14.14
14.29
14.29
14.21
14.36
14.36

Time frame of the above readings is five seconds.

A flat 12v is not fine for a car battery at all. A healthy one is usually around 12.5 -12.6v

I haven't charged it off the car overnight, but its a genuine VW battery and given I have invoices for wiper blades and other small items with the car and no invoice for a battery - its possible by some miracle that its the original one.

I haven't tested resistance down the charging cable back to the battery but I can do so now and will report back :) Thanks for help SS.
 
Charge it off the car first and redo that cranking test but disable it from starting first, Disconnect crank sensor or coil pack plug. (Ideally the crank sensor if it's accessible, as this will prevent injectors from firing)

It does look knackered but without charging it and letting it settle first you might well be barking up the wrong tree.

Clearly the car started as it rose up to 14v. So what's actually the problem..

A flat battery that isn't knackered will read about 11.6v I think.
Fully charged it should read the 12.6v you state.

Lastly, you may as well forget the resistance test I mentioned, vag com is clearly displaying a good 14.3v so the alternator charge is getting into the system fine.
 
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Thanks for the reply mate -

I wouldn't know how to disable starting for cranking as its a pd tdi engine. I can go to a battery place and get a drop test done I suppose.

Why am I flapping over it - Well it starts VERY slowly as in the actual crank speed is poor and I worry it won't start when I need it to.

I've always been of the mind that prevention is better than cure and as such if I can avoid it coming to the point where it just won't start I'll be very happy. I've looked at the battery and it has VW part numbers on it and only rated at 570cca (If I've interpreted the label properly).

The battery I want to replace it with is a Bosch Silver 5 with 800CCA. I realise batteries are expensive but at £79 delivered I believe this to be good value for a battery I have had on a previous vehicle and it never let me down.
 
Good value for money if it needs spending. Pretty **** poor if it doesn't. ;)

Anything from knocking the boot switch off when loading up with presents over Crimbo causing the boot light to stay on, to inadvertently leaving the ign key on or the parking lights on, or the alarm has been going off while unattended could have caused the battery to go flat. Just because it's flat doesn't mean it's knackered. :D
Charge it up, get a garage to do the drop test and if it fails that then purchase your desired battery I'd say.
 
Again, thanks for your reply. Problem is I'd feel cheeky getting a garage to do a drop test hoping to get a battery sale and then buying it from the interwebs!

The car is right outside the house so the alarm doesn't go off and the boot light doesn't work ;) The car is driven daily pretty much and usually at least 15/20 miles so it should be getting a reasonable charge.
 
All the Halfords I've ever been too can do a battery test using a handheld bosch device, I assume it's a drop tester as they input battery capacity etc and it simulates a load. If you know someone with a trade card, Halfords is good value for buying a new battery.
 
The more modern testers don't do a drop test (high load discharge) but instead to some sort of capacitance voodoo :D that tells you what state it's in.
But you will need to make sure you have charged it the day before for accurate results.
 
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numnutz said:
All the Halfords I've ever been too can do a battery test using a handheld bosch device, I assume it's a drop tester as they input battery capacity etc and it simulates a load. If you know someone with a trade card, Halfords is good value for buying a new battery.
Click to expand...

Halfords want £120 for an 096. I can get a 110 delivered for £79. I don't know anyone with a trade card either.
 
Have you tried the Battery megastore

http://www.batterymegastore.co.uk/

We use them at work for all our batteries. Run by a load of Polish people :D

Part Number: 096 (Yuasa)
Manufacture: Yuasa
Volt: 12
AH: 75
Cold Cranking: 650
£63.84 inc Delivery & VAT


Part Number: 096 (Exide)
Manufacture: Exide
Volt: 12
AH: 71
Cold Cranking: 670
£64.94 inc Delivery & VAT
 
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Nor me, couldn't find a 110 :D
Have you tried sticking your car details into the "search by vehicle" section...
I banged in golf 2L 2005 diesel and it came up with an 096...
Give em a ring, they are bound to do one it might just be called something else.
 
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