Battery voltage for a 1950 Minor

[Flintstone52]

Hi,
I have just acquired a 1950 Morris Minor with a side valve engine.
It was owned by a young lady who had it for 6 years, apparently it ran when she got it.
It does not have a battery.
It looks like it is still positive to ground.
I am guessing it is a 6 Volt system?
Can anyone advise me of the battery voltage please.

[simmitc]

No, all Minors are 12 volt. You can keep +ve earth or easily convert to -ve, the choice is yours. We will gladly guide you on any questons that you may have.

[Flintstone52]

Thank you for that info.

In the 1970's I converted a Mini to negative earth, as I remember it was a simple procedure.
Changing the direction of the starter motor and changing the residual magnetism of the generator field windings?

Would really appreciate a detailed procedure please.

[don58van]

Would really appreciate a detailed procedure please.

This article covers it.

https://mgaguru.com/mgtech/electric/et202.htm

Don

[simmitc]

As you will be fitting a new battery, check the terminal layout to ensure that you get the +ve and -ve on the correct side when fitted towards the bulkhead. see viewtopic.php?t=75708

[geoberni]

Would really appreciate a detailed procedure please.

This article covers it.

https://mgaguru.com/mgtech/electric/et202.htm

Don

Personally (I've read it before) I find that article quite long winded and it can put people off. It's also somewhat flippant about the need to reverse the Coil connections....

To be nice to the spark plugs, you should switch the two small wires on the ignition coil to make the spark jump the right direction across the plug gap. The engine will run as well either way, but the plugs should have a longer life with correct polarity.

Yes the engine will still run. However, failing to change the Coil connections WILL result in the plugs overheating and their life WILL be shortened. The spark will, according to many professional sources, be up to 50% weaker. See this discussion: viewtopic.php?t=70183

CAUTION - If the previous owners have added any electrical/electronic items these might be polarity sensitive, so just see if there is anything, eg a Radio.

That aside, the simple list is:
1- Turn the Battery around, however in your case it has no battery so buy one with the terminals in the right configuration, as per the link you've already been given. The Battery connections are different sizes, so you'll need to change end fittings over, or replace if they are crimped on.

2 - Flash the Dynamo as per the article instructions, to change the residual magnetic field polarity; although, since the car has been dead for so many years, even that is barely needed. But just do it anyway.

3- Change the Coil Low Tension Connectors over.

4 - Start car.

When it's all running, you can check the Coil connections are now right by doing the 'Pencil Test' in the link I just included.

[svenedin]

I would also add that if the car has a heater, the fan motor will run backwards with reversed polarity. It does actually still blow air but this is significantly reduced running the wrong way (centrifugal fan). I happen to have a heater on the table right now and I have been playing with reversing the polarity just to confirm this to myself. The wiper motor will also run backwards but this makes no difference to its operation.

Stephen

[geoberni]

I would also add that if the car has a heater, the fan motor will run backwards with reversed polarity. It does actually still blow air but this is significantly reduced running the wrong way (centrifugal fan). I happen to have a heater on the table right now and I have been playing with reversing the polarity just to confirm this to myself. The wiper motor will also run backwards but this makes no difference to its operation.

Stephen

Not necessarily.....A Permanent Magnet Motor will change direction, but not a Series Wound Motor with Field Windings.
A Series Wound DC Motor is often used as they are Self Exciting, they don't need a 'kick' in the required direction to get rotating and will always go in the same direction.

I've checked my aftermarket Tudor Heater and it doesn't care which way it's connected, the fan always rotates clockwise as viewed from the front.

20250213_144505.jpg (1004.76 KiB) Viewed 6646 times

It's all about the windings. The Car Starter for example, from recollections of the distant past, is a Compound Motor, having both Series and Parallel field windings.
The Starter always goes in the same direction because it's kicked that way by the Series Field, and the Parallel Field gives it the torque to turn the engine over.

[svenedin]

Yes indeed. The motor I was testing is a permanent magnet motor.

Stephen

[geoberni]

Yes indeed. The motor I was testing is a permanent magnet motor.

Stephen

Obviously not a standard approach between Smiths and Tudor; though both use a Rheostat to control their motors.