charging volts

jackster · 08-02-17, 12:02 PM

hi guys can anyone tell me what voltage should i have at my battery when sitting ,engine not running / then voltage at alternator and at battery when engine running.i seem to lose volts for starting. need some figures to give me guidelines.its possible i have a power loss somewhere but dont know where to start. audi 80 b4 1992 2.0e abk engine,hope you can help guys cheers.
ps replaced a electric aerial and central locking pump recently so if it keeps draining i will disconnect them for a while,

missfire · 08-02-17, 12:36 PM

Hi, normally about 12-12.5v on a good battery when sitting, and around 14v when running on most of these old things. 10v when sitting and it might need charged or changed.

Hanuman · 08-02-17, 02:05 PM

How are you measuring this? If you are using a voltmeter in the car's own instruments, then you need to make sure that it is accurate. If you are measuring using a calibrated DVM/AVO etc, then it would help if you wrote those values.

A strong battery should be able to maintain the 'Volts' while cranking, when current drawn is high. A weak battery will not.

jackster · 08-02-17, 04:56 PM

I'm at work till 10pm ,will check again tomorrow,but the battery was sitting at 13.6v when charging on car.12.6v after sitting for a while.but seen on my volt meter that I just purchased from a dealers that the voltage was erratic at the first time on looking.it would go from 11.5v to 12.4v but now has the first set of readings. Upon trying to start the dash lights would be dull.then go off all together when starting ,sometimes just get a click ,cheers

esseff · 08-02-17, 05:10 PM

I had a voltage drain on my first 2.0E and after pulling fuses one by one and left overnight it turned out to be something in the central locking circuit. Vacuum pump running on, maybe. I couldn't be bothered to work on it outdoors so just used the key for the driver's door and manually locked the others by their buttons. I think the alarm is disabled by the same fuse.
Another thought - it might be worth folding down the rear seat and looking to see if the boot light is stuck on.

4v6 · 08-02-17, 06:32 PM

Usual voltages are 14.0 volts, but a better test is to turn on all non pulsing loads, so thats heated rear windowm interior blower heater fan, headlights all on and full beam, and see if the alternator maintains that voltage.
If its dropping down to 12 volts or lower then the alternators not keeping pace with the loads it needs to maintain so the battery will tend to get discharged.
If its ok then the battery may be suffering from sulphated plates where itll not hold a decent charge for any length of time.

Easy way to test for battery drains is to remove one of the battery terminals and connect an ammeter between the terminal removed and the battery pole and see if theres any appreciable drain, anything more than a few miliamps suggest something like a boot light staying on? or other excessive drain.
Without starting the car after its gone cold, touch the outer casing of the alternator, if its warm then internals have developed a fault and will need replacing, seen that one before on an Austin Montego amongst others. hth.

jackster · 08-02-17, 08:15 PM

Good shout and info guys will be checking all this out hopefully tomorrow if its not peeing or snowing cheers guys much appreciated.

jackster · 10-02-17, 11:15 AM

car seems to be starting just now but will do a drain down check soon get results up . cheers .

08-02-17, 02:05 PM	#3
Hanuman Trickster Classic Audi Club Member Join Date: May 2009 Location: Heckling from the cheap seats, Phnom Penh, KoW Posts: 7,006	How are you measuring this? If you are using a voltmeter in the car's own instruments, then you need to make sure that it is accurate. If you are measuring using a calibrated DVM/AVO etc, then it would help if you wrote those values. A strong battery should be able to maintain the 'Volts' while cranking, when current drawn is high. A weak battery will not. __________________ I wish they would keep the damned Chinese away now that I can go home, so that I can enjoy Fish amok and a draught Angkor

08-02-17, 06:32 PM	#6
4v6 Ex Member Classic Audi Club Member Join Date: Dec 2007 Posts: 5,565	Usual voltages are 14.0 volts, but a better test is to turn on all non pulsing loads, so thats heated rear windowm interior blower heater fan, headlights all on and full beam, and see if the alternator maintains that voltage. If its dropping down to 12 volts or lower then the alternators not keeping pace with the loads it needs to maintain so the battery will tend to get discharged. If its ok then the battery may be suffering from sulphated plates where itll not hold a decent charge for any length of time. Easy way to test for battery drains is to remove one of the battery terminals and connect an ammeter between the terminal removed and the battery pole and see if theres any appreciable drain, anything more than a few miliamps suggest something like a boot light staying on? or other excessive drain. Without starting the car after its gone cold, touch the outer casing of the alternator, if its warm then internals have developed a fault and will need replacing, seen that one before on an Austin Montego amongst others. hth. Last edited by 4v6; 08-02-17 at 06:34 PM.

08-02-17, 12:36 PM	#2
missfire making wooden things Classic Audi Club Member Join Date: Dec 2009 Location: cow land Posts: 8,154	Hi, normally about 12-12.5v on a good battery when sitting, and around 14v when running on most of these old things. 10v when sitting and it might need charged or changed.

08-02-17, 04:56 PM	#4
jackster Grown up member Join Date: Nov 2016 Posts: 73	I'm at work till 10pm ,will check again tomorrow,but the battery was sitting at 13.6v when charging on car.12.6v after sitting for a while.but seen on my volt meter that I just purchased from a dealers that the voltage was erratic at the first time on looking.it would go from 11.5v to 12.4v but now has the first set of readings. Upon trying to start the dash lights would be dull.then go off all together when starting ,sometimes just get a click ,cheers

08-02-17, 05:10 PM	#5
esseff Grown up member Classic Audi Club Member Join Date: Jul 2010 Location: Castle Donington Posts: 57	I had a voltage drain on my first 2.0E and after pulling fuses one by one and left overnight it turned out to be something in the central locking circuit. Vacuum pump running on, maybe. I couldn't be bothered to work on it outdoors so just used the key for the driver's door and manually locked the others by their buttons. I think the alarm is disabled by the same fuse. Another thought - it might be worth folding down the rear seat and looking to see if the boot light is stuck on.

08-02-17, 08:15 PM	#7
jackster Grown up member Join Date: Nov 2016 Posts: 73	Good shout and info guys will be checking all this out hopefully tomorrow if its not peeing or snowing cheers guys much appreciated.

10-02-17, 11:15 AM	#8
jackster Grown up member Join Date: Nov 2016 Posts: 73	car seems to be starting just now but will do a drain down check soon get results up . cheers .