Is my battery overcharging?

[Rasputin]

When getting into my pickup ,I noticed an acid smell,and opened the bonnet to find what looked like condensation on and around the battery.I immediately removed the battery and nuetralised the acid with bicarbonate of soda.On checking the battery,two cells were completely empty of acid and the rest were fine.What could have caused this? The pickup has been running normally,without a hint of electrical problems.Could the Alternator be overcharging? If so how do I check it and what sort of meter would I have to buy?I assume the battery has had it,I am reluctant to buy another one only to cook that one.

[bmcecosse]

I suspect a dead cell or two in the battery - has caused the 'overcharging' in the other cells. Alternators are much less liable to overcharge than dynamo systems - where a stuck contact will certainly throw the volts up. You will need another battery - connect it (right way round!) and run the engine - checking the volts with a meter. Should rise to 13.8/14 volts at decent revs, and still hold the volts with headlights and heater on.

[mike.perry]

New battery should be for neg earth, therefore the posts are the other way round to normal poss earth Minor. Neg post at the back on the right

[Rasputin]

Thanks for the replies,what sort of meter should I get,as I know nothing about electrics.And incidentally,the battery is only eight months old! Also the regulator box is still fitted,but has been fine for fourteen years to my knowledge.

[bmcecosse]

Simple multi meter from maplins should be fine. If only 8 months old - take it back for refund! This is fine.... http://www.maplin.co.uk/digital-multime ... test-44679

[Rasputin]

Ok have bought multimeter and new battery.Tested battery with engine running,meter crept up to 16.99 and I turned off immediately.Does this mean my alternator has had it? I do have a lucas LRA100 Alternator which was nearly new when I took it off another Morris a few years ago,is it a sraight swap?I would like to keep the control box if possible.

[bmcecosse]

Certainly 16.99 is WAY too high....... What 'control box'... how is the alternator wired up......?

[Rasputin]

Regulator box (or whatever it`s called) is still fitted and connected up,could this be causing the overcharging? I,m not sure exactly how it`s wired up,and it`s too dark to check at the moment.

[bmcecosse]

The Reg box can be retained - but not used in any way to control an alternator... It is just a handy connection point for various wires. You need to look at the alternator - tell us what wires there are, and where they go ........

[Rasputin]

All sorted The Alternator that I had "in stock"was exactly the same as the one I took off.On revving the engine the voltage rose to 14.5.Thanks for your help.

[bmcecosse]

Well done - but how unusual! I've never heard of an alternator overcharging like that.

[Matt]

I have - on plenty of occasions.

The other favourite is the diodes failing and flattening a battery overnight

[MarkyB]

What needs to be replaced to make it work OK again Matt?

[bmcecosse]

Diodes failing - yes of course. but not overcharging. You can probably buy a kit to overhaul the thing on ebay - start searching. I'm only familiar with the older ACR Lucas range -and kits for them are certainly available.

[lambrettalad]

Diodes are the achilles heel of alternators ,especially AC Delco where the diodes are exposed to more heat than the Lucas ones,because of the position.Sometimes they would last ages at others 2 weeks And that was proper 1970's stock

[Matt]

On the other forums I am on (mainly Transit) we get posts about alternators putting out 15V+ every few months.

These are normally on Lucas A127 alternators (very similar to the ACR). With regards what to replace... no idea, never had an alternator overcharge on one of mine.

I have also had a minor with an ACR alternator putting out between 14 and 16.5V (dependant on RPM), this was replaced with a 2nd hand unit which worked straight away.

[katy]

On the other forums I am on (mainly Transit) we get posts about alternators putting out 15V+ every few months.
These are normally on Lucas A127 alternators (very similar to the ACR). With regards what to replace... no idea, never had an alternator overcharge on one of mine.

It sounds like the internal voltage regulator is at fault and needs to be replaced.

[bigjim]

IT IS THE INTERNAL VOLTAGE REGULATOR anything else wouldnt charge it is the ONLY thing that can cause overcharging