Switching from 6V to 12V, voltage regulator?!

[Special Bits]

I converted a car by replacing the cutout with an RB106 (using only the cut out part of the unit - it's not hard to work out), winding the 3rd brush right back, replacing the bulbs & battery and that was it. Worked fine. It didn't have a wiper motor and horn was higher! You don't get the benefits of electronically controlling the dynamo but it still charged ok. If you do this always have a spare set of starter brushes with you - a 6v starter on 12v eats brushes (1930 type starter)

Charles

The Ulsteroid is similarly modified, a £25 voltage control unit, a bit of minor rewiring and a 12v coil, job done! The Voltage control unit must be of a type which only allows 11A output, these are readily available from suppliers of old tractor parts.

Advantages to me, cheap and easy conversion to LED bulbs. The ability to run a tyre pump, navigators map light, phone charger etc from a hidden bank of sockets. In 20 years of sporadic use the starter motor has been fine running on 12v without any modification. Likewise the wingdings of the dynamo. We did have a charging problem on the Lands End trial, but that turned out to be a faulty voltage control unit. To put this into context, the car is now used for MCC trials, which involve 200+ road miles including running for most of the night. Whilst the 6v system can be made to just about cope with running all night, the additional needs of competition do become a problem.

Stuart

[PaulS]

Stuart,
Did yours also only use the RB106 cut-out part and stick with a switched in/out resistor to limit field current? I am just looking at doing the same. I am building a special from a pile of bits and have no electrics at all to start with except dynamo and starter so decided to go with 12V. (I feel I needed to make that point clear).

Paul

[jansens]

Paul, I am also using 12v and a RB-106 for my special. I am still working out exactly the best way to do it. It is possible to use the cut out and the regulator. I am still working out how to do the resistor part. The resistor is just there to provide two different charge levels (the summer and winter setting).

One thing you can do to the RB-106 to help reduce arcing is put a snubber diode across the regulator coil. This document explains that (and lots of other useful things): https://www.mgexp.com/phile/3/191288/REP..._RB106.pdf

Also Moss Motors have some good (oddly relaxing - it's the guys calm voice) films on the RB-106 and how it works and how to adjust it. This is one of them, there are others too.



When I get mine setup I was going to make sure the regulator voltage is correct for the battery. A lot (most?) 12 volt car batteries sold now are the Calcium Lead acid type. As far as I can tell they charge just like a normal lead acid under normal conditions. I was basically going to set the regulator to give 14.2 - 14.5 volts. 

You can have issues if Calcium batteries are very discharged in which case you need a charger capable of specifically charging Calcium types to recover them. I bought a new charger a few years ago and it does indeed have a Calcium setting on it and I always wondered what that was for. It gives LESS oomph during the absorption part of charging then a slightly higher float charging voltage.  

The battery I bought was a 12 volt Century so I am going by the information they provide here for  charging voltages and so on: https://www.centurybatteries.com.au/cont...arging.pdf

The Calcium type are supposed to be more resistant to overcharging apparently which might be a plus in an older, mechanically voltage regulated car.

Simon

[Bob Culver]

Others have reported that timing gears rattle with electromagnetic regulators. Directly switching 12 v to a field intended for about 4v is crude and brutal. There is nothing to prevent full continuous field current when system volts low and that should overload dynamo, although many claim no problems!

Pure musing but many 12v conversions simply wind the 3rd brush back to retain 8 amps peak charge. Unless the switching action wears the brush I do not see why the 3rd brush cannot be retained, wound back, and fed from the regulator F terminal.
Books set old regulators at curiously high volts cold. I monitor the car battery in normal runnng and tweak for about 14.2. Enables use of digital meter. 
Most single coil regualtors incorporate a current overwinding which reduces output under load to preserve the original matched dynamo. With peak field current set by some other means this feature a complication.