strange reading on battery

[Choppski]

Evening guys,

i've recently serviced my van as it is now in storage for the darker months. went to start it the other day and the battery was flat. i do have an alarm on it and didnt run it for over 2 weeks. i jump started very easily and the battery isn't flat if i turn her over once a week.

However, on the last fire up i decided to test the voltage on the battery to check she is charging ok. started off at 13.5V and then slowly climbed up to 14.5v after 4-5mins as the engine warmed up. after 10 mins i got a reading of 15.5v and it kept on rising to 17v at which point i switched off and started to type this message. i've never seen the voltage climb so high. engine was just idling along nicely, no hard revs.

thoughts?

[Oldiebut goodie]

Interestingly I had this happen 2 days ago on a battery in the workshop that I use for testing bits and pieces, I was getting over 15v also on charging with a mains charger. The problem was that it was in dire need of a drink - electrolyte was well below the level marks. Topped it up and it then was back to charging at just over 14.4v.
Worth checking the electrolyte level for a start. If it is a sealed one you are stuffed with that check though. ( I have had to ditch loads of these so-called maintenance free ones which, upon opening up, are drying out) I try to avoid buying them now but it is becoming harder to find unsealed ones in some sizes.

[Choppski]

Thanks Oldie - will check that out.

i fired her up last night and the same problem occurred.

Will let you know how i get on.

Thanks,
Paul

[kevtherev]

A failed voltage regulator will also cause this issue.
Often followed by blowing bulbs etc

[Choppski]

Kev - where would a voltage regulator live in the van/ engine bay?? is there a simple test i can perform on it to diagnose it with a multimeter?

ok - quick google check (i was being lazy) - its on the alternator. i'll check if its a bosch - they seem to be about £4-£8? sound about right?

Still is there a good test i can perform to see if that is the issue?

[slowcoach]

I've had this too, 18v while driving. Battery was fizzing and stank! Very high speed wipers was the first clue. No long term damage, but swapped the regulator on the back of the alternator and all was well. Just a few pounds for the part.

[kevtherev]

Still is there a good test i can perform to see if that is the issue?

You already did it really.
But any more than 14.2V at the Alternator and it's in the frame
Oldie has a point though, dry cells will also cause the reading

[California Dreamin]

Still is there a good test i can perform to see if that is the issue?

You already did it really.
But any more than 14.2V at the Alternator and it's in the frame
Oldie has a point though, dry cells will also cause the reading

14.5 volts on many 'replacement' voltage regulators....although you won't will see anything like that at the battery (petrol vehicles)
Remember, leisure batteries connected to the main starter battery can also be responsible for spurious readings, however, easily eliminated by disconnecting.

Martin

[neil3965]

One more thing to check - is the battery in the multimeter OK?

I recently got 15v plus when checking starter battery, couldn't find anything wrong, checked the 9v battery in the multimeter, it was down at 8v, replaced it, starter battery was back to normal!

[Choppski]

Hi guys, just thought to post an update on this issue.

Basically it was the 'maintence free' battery - probably a dead cell as when swopped with a new one problem solved....well kind of. The voltage stablised but was a little low - 13.8 to 14v. So i decided to take a look at the voltage regulator as suggested earlier in the posts and guess what, the two carbon prongs were on their last stubs approx 5-7mm. So i bought a new top quality item from Brickwerks - ala club discount - and received a nice shiny new one, with two much longer prongs. Fitting was simple (apart from having to remove the alternator as i have damn tight screw on back and had to spray plus gas like holy water at a baptism and the stubbon air tubes into alternator housing). I also changed the battery on the multi meter as well!

Guess what - nice stable 14.5v charging a new battery.

feeeeeeling goooooooodddd.

Thanks for all your help.