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MG MGA - Voltage Regulator RB106/2

As many of you will know the Workshop manual states the voltage setting of the regulator should be between 15.4 and 16.4 volts assuming all mechanical settings are correct and the unit is otherwise working normally.
However calcium battery’s used these days need a maximum charging voltage of 14.2 volts to prevent boiling of the electrolyte or damaging the plates. However setting the regulator to 14.2 volts, means with the headlamps on the battery is not being charged. With them off a trickle charge of 1.2amps is shown.
Any ideas anyone?
J Hughes

Go to "worldphaco.net" there are several very detailed articles about the RB106 and modifications. I have made the transistor, diode, and resister modification on several units and am pleased. Also look at reversing the A and A1 connections as explained in the articles.

Regards,
Brian W.
ZBMan

Brian,
Thank you for this fascinating web site. While a little beyond my technical expertise, I can appreciate the benefits of an electronic regulator. Do you modify the old regulators? And if so, at what cost?
Bayard
Bayard DeNoie

Yes thanks Brian for the link. I’ve started to look around for a spare regulator to do the mods on rather than end up with the car off the road.
J Hughes

J Hughes, what makes you think that the battery is not already fully charged? I have set my RB106/-02 control box for ~13.8 nominal (headlights off) and never had any issues. Definitely use a good analog meter. Digital Meters are sometimes suspect to noise interference giving erroneous readings. My 12V batteries last about 10 years before needing replacement.
Chuck Schaefer

I think I have some spare regulators, if anyone wants to experiment.
Dave O'Neill 2

Hayward:
I have not considered doing these conversions for others in a commercial fashion. If you are a bit handy and careful and not ham- fisted, then once you order the electronic pieces( available on the web from various sources) - it's not that difficult. You do have to know how to properly and quickly make a proper soldering joint to avoid damaging the components. You only need a single transistor, a diode, and a 100 ohm resistor for each conversion. Not a lot of money. You do also have to take the regulator apart and clean the points flat and do a proper mechanical assembly and initial mechanical setting of the points, so you need a feeler gauge.

Good luck and let us know if you try it! Don't be scared! Take your time and don't rush through it and you should be fine!

Regards,
Brian W.
ZBMan

Hi Chuck and all. Since my last post I’ve been playing some more, both with a discharged and fully charged battery. For instance with a discharged battery and the regulator set at 16volts with all lights, heater etc on and 2300 RPM the charging current was +9.4amps and battery volts measured (at the battery) was 13.8.
With all electrics off current was 13.2A and volts 14.0 (Yes it is a Digital Meter but a top range Fluke).
The readings for a fully charged battery were: All electrics on: .3A and 15.4V. All electrics off: .4 and 15.1V.
I’ve now set and running with the regulator at 15volts to keep the charging voltage (at the battery) to below 14.5V on a fully charged battery and see what happens.

Thanks for the offer Dave please keep them handy as I may have a go with ZBMan’s conversion.
J Hughes

This thread was discussed between 16/07/2015 and 11/08/2015

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