Alternator over charging?

BMCC · Post by **BMCC** » Fri Mar 14, 2014 8:40 am

Well they say it always happens in 3's

I've tested the battery this morning and it is 14.5V with the engine off. When running (just after start up) it was 17.7V charging. Seems very high to me. The manual says anything over 18V and your in danger of causing electrical faults.
The battery was charged during the week although the little light indicator is still showing black (It is a sealed battery from Honda so I don't think you can add the necessary water, may still be possible though as there are some caps up top on the battery which may come off with gentle persuasion to see what is underneath).

The question is though could the voltage regualtor be knackered in the Alternator? Or is the fact that the battery has just been charged messing up the readings I am getting?

What do you guys think?

Post by **Donald** » Fri Mar 14, 2014 9:44 am

If the regulator is duff will it not over-charge the battery anyway? I'm not sure how these things work exactly (this is probably pretty obvious), but I'm assuming the regulator works as some sort of resistor, and as soon as it stops working properly it lets all sorts happen?

Wouldn't have thought if it had just been charged (assuming you charged it off the car) it would be reading over as these things have a cut-off in them to prevent this sort of thing happening?

BMCC · Post by **BMCC** » Fri Mar 14, 2014 12:21 pm

I think the regulator is knackered hence the 17.7V although this is at the battery. I'll test the output voltage from the alt and I'd reckon that anything over 15V seen as the battery should charge at about 14.8V then the regulator's knackered. I think the 14.4V I am getting now from the battery may just be the excess from the charge I gave it. What concerns me is the fact that the battery indicator (that little green light) is black possibly indicating that the water level is low in the battery due to it being overcharged.

Just got the car up and running again and I reckon I'll have to park it up till I get to the root of the problem. I've got a spare meter just in case the one I am using is duff.

Post by **Vtecmec** » Fri Mar 14, 2014 1:06 pm

I bought a voltage regulator off ebay for my alterantor for less than £15 delivered, so not too costly if it is that.

BMCC · Post by **BMCC** » Fri Mar 14, 2014 1:11 pm

Vtecmec wrote:I bought a voltage regulator off ebay for my alterantor for less than £15 delivered, so not too costly if it is that.

How easy was it to swap out?

Post by **Vtecmec** » Fri Mar 14, 2014 1:29 pm

Very, though my alt was off the car, I can't see it being anymore than 30mins on the car.

Post by **Vtecmec** » Fri Mar 14, 2014 1:33 pm

http://www.ludegeneration.co.uk/profile ... 0-190.html

Some pics here, the bit with the plug and cooling fins.

Post by **Thebusofwoe** » Fri Mar 14, 2014 1:37 pm

It will be the regulator unit inside the alternator chap. The 14v ur getting from the battery will be surface charge/voltage from having it charged. Now the black eye could indicate a faulty cell. So if it was me, i would replace the regulator unit/alternator, and poss change the battery depending on how it behaves after you have fixed the alternator.

89 UKDM BA4 4WS (resto job!) · Post by **wurlycorner** » Fri Mar 14, 2014 1:58 pm

That's the alternator regulator going down.

If it's charging the battery at 17-18v, it'll probably have started to boil it dry, which would be why the indicator is black.

Batteries these days are generally 'maintenance free', which means you can't take those caps off to top up (not in a way that you can then refit them after, anyway!).

Post by **Donald** » Fri Mar 14, 2014 2:07 pm

I suppose you could recoup some money by selling it to the Iranians as an easily portable hydrogen bomb.