DDK - Die Deutschen Klassiker

I had another ignition system query - thoughts really welcomed as ever.

I am replacing my existing 6 volt battery but decided to test the voltage of the current battery out of interest after the car stood for a week - it was reading 4.5 volt. I checked the cells and they have boiled dry. Basically knackered.

Within a year and a half I have had one battery explode and another fail. Assuming it isn't just a consequence of not using the car enough and/or bad batteries I am wondering if the voltage regulator isn't calibrated correctly.

It's a reconditioned unit and was also checked by an automotive electrical engineer after I had the battery explode and he said it was working fine.

We checked the voltage coming out of the regulator to the battery. The voltage does seem to drop off after the engine has been running for a while so it seems to be working. We also took the top off and engaged the points manually. In each case it went from about:

- 6.7 volt to 6.8 volt at 1,600 revs
- Dropping off to about 6.38 volts when the regulator engaged

I'm going to get it checked again but wondered what sort of drop you might expect in voltage if the regulator is operating correctly. Seems to me at the moment like I'm always charging the battery.

The generator was producing about 4.5 volt at 1,600 revs. I also wondered how much of the voltage we saw at the regulator could be attributed the charge of the battery itself. As I assume the regulator only turns on and turns off charge to the battery.

Cheers

Phil

I've got the Henry Elphrink manual which gives detailed instruction on checking the generator and regulator and it's easy, so buy a new battery, get a manual and a test meter and check the system.

Cheers for the tip Ashley. I think I actually have a VW generator / regulator set up we have the Haynes manual for Beetles and did the tests in there.

I suppose my lack of understanding about the whole thing is - assuming the regulator is working fine - if you test the voltage at the regulator when it has cut in and stopped passing the charge from the generator (as it reads the battery is fully charged) will the voltmeter show just the charge in the battery?

This would make sense to me as there should be no charge coming in from the generator.

Thanks all for any thought on this!

Phil

Assuming it's similar to Lucas, which I have experience of, all the regulator does is keep the voltage around six volts because a six volt battery doesn't like a lot more. Volt's rise with revs. It's possible yours wasn't holding the voltage down and the battery was damaged as a result.

The only time the regulator disconnects from the battery is when battery voltage exceeds what's coming from the Dynamo. In other words when the ignition warning light flickers at tickover. Otherwise the charge is constant.

FWIW, if yours is not a sealed for life battery you need to keep an eye on acid levels.

I can test when I get home but from 800rpm onwards I think I get 7+ volts

Sent from my X5pro using Tapatalk

Neil, Ashley - Cheers. Had a chat with the auto electrical engineer and he reckons its all working correctly. So I think I'll put the damaged batteries down to lack of use rather than over-charging.

Neil, I'd be interested to hear what charge is going into your battery if you get a chance at some point. Just for reference.

Cheers

Phil