DVR Regulator and DFL Dynamo

[Charles P]

I’ve been usefully busy over Christmas and have fitted a DVR3 electronic regulator to my DFL dynamo equipped car. The dynamo is now converted to 2 brush and I have a 3ohm 50 watt resistor inserted with the field coils to create something nearer adequate resistance. The problem is that on garage testing I’m seeing the ammeter run up to 15amps, which can’t be good.
Is the problem that 3 ohms isn’t enough or is it something else? 
That’s what seems to be suggested in this thread
https://www.austinsevenfriends.co.uk/for...r#pid26689

It would be useful if a higher powered resistor solved the problem but I’m much happier with mechanical things that electrics or even electronics, hence the request for helpful suggestions 

Thanks

Charles

[JonE]

what was the background resistance on your DFL field coils, out of interest? There was a post which discussed the later dynamo models(and how low the resistance was on both the 2 and 4 pole models); I'm wondering whether the earlier dynamo was any different in terms of the extra needed in the equation for these 2 brush working situations.

[Charles P]

what was the background resistance on your DFL field coils, out of interest? There was a post which discussed the later dynamo models(and how low the resistance was on both the 2 and 4 pole models); I'm wondering whether the earlier dynamo was any different in terms of the extra needed in the equation for these 2 brush working situations.

1.7 ohms

C

[JonE]

Robson and Francis said that 12V wants about 5 ohm, so perhaps you are a bit low. They had warranty problems with the former model DVR3 (before the new owner) and now use a different regulator with a larger heat sink. That was a few years ago...

They of course advocate new windings, otherwise you are going to revving higher to charge. Is the DFL 4 pole or 2?

It is one of the reasons I'm staying with 6V on the DEL, because its less efficient/more expensive to convert to 12V windings!

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This might also be useful from Mike Hutchings... I was targeting the lower cost units so I could carry a spare, and also didn't think I needed the higher car output. I'm presuming the second bit is universal to either unit but may be wrong.

"I would not advise using a DVR2 to control your dynamo, without a new field winding anyway. The DVR2 is really designed with motorcycles in mind. It does not have output current limiting, so unusual electrical demand would overload the dynamo (larger flat battery and the increased electrical loads on the car).

A series resistor will probably increase the engine speed required to provide any useful charge. The resistor will add its own dissipation and further reduce efficiency. But I do not have direct experience of trying this addition".