15V to 14.8v AGm battery - Too high?

I just noticed my alternator is starting to put out 15v on start up and after 10 or so mins driving it would drop back to 14.8.

Yellow top Optima AGM, pretty new batteries.

Is that too high or is my alternator on its way out?

Might time for a new one and keep this as a spare for the Simpson anyway.

I can't answer your question mate but have you checked multiple meters to make sure it's not a misread?

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Originally Posted by Winnie

I can't answer your question mate but have you checked multiple meters to make sure it's not a misread?

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Yeah definitely mate, I too was questioning my gauges and used two different multis and all three were same.


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I am not an expert but I believe an AGM cherge voltage up to 15v is good.

Darren probably knows more

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Originally Posted by TPC

I am not an expert but I believe an AGM cherge voltage up to 15v is good.

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Yeah I’ve read a lot of things on the internet with AGM and it’s such a mix bags of lollies with advice.

I understand AGM are ok with that charge but it’s only just come on so why I guess is my question.


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Hmmm. Sounds High. A quick google tells me what i already though and that it may be a faulty Voltage regulator, if this is the case it is probably a very simple fix and any Auto Elec could sort that out quickly.

I did read though it could be a faulty Earth or Neg point. disconnect the battery and disconnect the earth off the Alternator and clean and reconnect and see if that fixes it.

Here is a quick vid to show removing the voltage regulator

https://www.youtube.com/watch?v=VBvtBoceq00

This is also a very good vid mate. Watch this from the start but also the 8:50 minute mark he speaks about the Voltage Regulator.

https://www.youtube.com/watch?v=1bK0De9XOP0

I would not be buying a new Alternator just yet.

Thanks mate, it does sound high but looking the Optima’s website says it’s in range but, at highest point that’s for sure.

https://www.nissanpatrol.com.au/foru...2024/05/31.jpg


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Interesting they also mention up to 15.6v for a rapid charge.https://www.nissanpatrol.com.au/foru...2024/05/32.jpg


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It's definitely something you need to get sorted out before the big trip though mate!

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