Battery Voltage Reading

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AK-Hull
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Battery Voltage Reading

Post by AK-Hull » 21/03/18 11:12

Hi guys,

I bought and fitted a new battery and the reading it's giving me is 17V. I've been told that this is far too high and will fry my battery after a while, and to buy a new alternator as the regulator on this one is likely to be gone.

However I've just had a comment on the owners club facebook page that 17V is fine.

I'm still relatively new to this scene, so could anyone please clear this up for me?

Thanks in advance.

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Re: Battery Voltage Reading

Post by jimi » 21/03/18 12:04

AK-Hull wrote:
21/03/18 11:12


However I've just had a comment on the owners club facebook page that 17V is fine.
I wouldn't believe farcebook if it told me it was raining!
If your measuring the voltage with a reliable digital multimeter then yes 17v is far too high. You should get around 14.6v with the engine running
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Re: Battery Voltage Reading

Post by Gazza_DJ » 21/03/18 13:07

17V is way too high. 15V would be as high as I would be happy with if I had upgraded 'The Big Three' and electrical load was low when measuring.

As Jimi says 14.something is more normal, dipping to 13's in a high load situation - headlights on, heater fan on full, radiator fans on, intercooler fans on etc.

17V = your alternator (voltage regulator) is dickered.
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Re: Battery Voltage Reading

Post by AK-Hull » 21/03/18 13:22

Thanks guys I'll get one ordered

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Re: Battery Voltage Reading

Post by jimi » 21/03/18 13:56

Not sure if the MK2 has a voltmeter on the dash (MK1's have) if so don't rely on it to be accurate because they notoriously inaccurate, hence why I mentioned usinv a multimeter ;)
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Re: Battery Voltage Reading

Post by Gazza_DJ » 21/03/18 14:00

MK2 NA's have one. Turbo's have an equally inaccurate boost gauge there instead :laughing

While the built in voltmeter is useless for an absolute measurement, it can tell you when something isn't right as long as you know where it sits most of the time. Absolutely not to be relied on though as you say!
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Re: Battery Voltage Reading

Post by AK-Hull » 21/03/18 14:04

Just out of interest, I fitted the new battery last weekend and I'm working away until Friday - the new battery isn't going to be completely ruined by the time I fit the new alternator next week is it?

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Re: Battery Voltage Reading

Post by Gazza_DJ » 21/03/18 14:18

If you're not planning on using the car, it'll be OK.
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Re: Battery Voltage Reading

Post by jimi » 21/03/18 14:41

Gazza_DJ wrote:
21/03/18 14:00
MK2 NA's have one. Turbo's have an equally inaccurate boost gauge there instead :laughing

While the built in voltmeter is useless for an absolute measurement, it can tell you when something isn't right as long as you know where it sits most of the time. Absolutely not to be relied on though as you say!
Spot on, great as an indicator of change from normal useless as a measurement device
Just out of interest, I fitted the new battery last weekend and I'm working away until Friday - the new battery isn't going to be completely ruined by the time I fit the new alternator next week is it?
You should get away with short journeys of a few miles but I'd avoid anything longer. Keeping your lights on would help. As Gaz says if your not using it then it should be fine
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Re: Battery Voltage Reading

Post by jeff » 21/03/18 16:10

what no one appears to have asked is where you are getting the reading from, it suggests you don't have a multimeter, so i assume your just using the battery gauge, which as others have stated is there just to show the battery is working :)

btw, we only have a facebook page for a presence on that spying platform, you maybe mistaking the club on there as being part of this one, which it isn't

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Re: Battery Voltage Reading

Post by MR2DI4 » 21/03/18 20:50

Gazza_DJ wrote:
21/03/18 14:00
MK2 NA's have one. Turbo's have an equally inaccurate boost gauge there instead :laughing

Works alot better at 15 to 17psi when the needle hits the top of the gauge.

Never had a problem with the stock gauge, its a whole lot better than nothing which is what you get from the factory these days.

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Re: Battery Voltage Reading

Post by MR2DI4 » 21/03/18 21:19

You want about 14.4 to 14.8V at idle with a charged battery. Got 14.6V last time I checked on the Turbo.

The charging system on these older cars is pretty crude, I notice on my 2004 Subaru it monitors the state of your battery charge and also what the alternator is running to control the charge voltage. It can be up a 14.4V after starting then you will see it drop to like 13.8V if you don't have the fan or radio on. Freaked me out the first time I thought the alternator had packed up. Obviously some fuel savings by not running the Alternator as hard full time and probably better life from the alternator as well.

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