Alternatr overcharging?

[wingdiver]

Hi
I have recently replaced the batteries and installed a decent battery monitor.
I noticed that, when the engine is running, the charging voltage goes up to around 14.8 rather than the maximum would expect of around 14.2 volts.
I have replaced the regulator and it is still the same. I have also removed all the connectors, cleaned everything and replaced them.
Any idea as to what could be the issue? Alternator is shot? Sensing lead not connecting/working?
Thanks in anticiaption.
Oh, and the alternator is a Prestolite A127-MT 12v/55A

 

[pvb]

Firstly, have you double-checked the voltage at the battery terminal with an independent multimeter?

I'd normally expect a Prestolite regulator to control at around 14.3 +/- 0.2 volts, so up to 14.5 volts. I'm not sure whether there's any temperature compensation built into that regulator, but colder operation may increase charge voltage.

Many people spend lots of money on add-on "smart" regulators to try to achieve 14.8 volts charging, so if you're getting it already, that's a bonus! It shouldn't harm your batteries in normal operation.

 

[wingdiver]

Thanks for the reply.
To expand a little......

I am now using a decent BEP Marine DCSM which monitors engine and domestic batteries amongst other things. It read as high as 14.8v.

My Victron Battery charger control panel also shows an 'overcharging' warning light.

Engine and domestic batteries have all been replaced in the past year or so. The light on the Victron panel came on previously but I didn't have the gauge to correctly identify the voltage.

The alternator is probably the one that was installed with the replacement engine in around 1999.

Changing the regulator was the first thought but has had no effect.

I read somewhere that a sensor lead plugs into the regulator and, if there is an issue with this, the output could be excessive. No idea what to do/check etc here.

Other than that, I assume a removal of the alternator for checking is the next stage but that will be a pain and cost £s to get checked so I'd rather find out what I can do with it in situ first.

 

[pvb]

I read somewhere that a sensor lead plugs into the regulator and, if there is an issue with this, the output could be excessive. No idea what to do/check etc here.

If the alternator has a battery-sensing lead, it's possible that a connection fault in that lead could affect the alternator voltage. You need to look for a wire emerging from the alternator and leading to the battery terminal.