Up until electric starters became popular it would not be correct to speak of a car's electrical system. Some had magneto ignition and gas lamps and had no battery at all. Model Ts ran off their flywheel and usually had no battery, their voltage could go up over 20 volts.
When starters and electrical systems came in they could be up to 24 volts.
It was only in the mid to late 20s that 6 volts became standard in the US. At the time a car might not have any electrical equipment other than lights and starter.
The 6 volt probably became popular because that was the cheapest battery that would provide satisfactory performance.
When they went to 12 volts in the mid 50s cars had changed radically. Their high compression V8s required more voltage for starting and hotter ignitions. Plus the many electrical accessories required miles of wire. The wire size could be reduced by half if 12 volts were used. This saved a lot of copper in a year's production of cars.
Plus, the new vinyl insulation was a lot better than the old rubber stuff. Meaning less possibility of short circuits when the wiring got old.
Incidentally many 6 volt cars had 4 volt coils for easier starting. That trick did not start with 12 volt systems.
Why English cars had 12 volt batteries I don't know. In the 50s it used to be amusing to look under the hood and see this great big battery and tiny engine. In some cars the battery was practically as big as the engine. Quote:
Peter Packard wrote:
G'day all, This should be an interesting topic as I'm sure that many of us are not quite sure why US auto manufacturers settled on 6V electrical systems and why they changed to 12 V systems. I have read a number of articles in the SAE Journal over the years. Owen-Dyneto and others are sure to have some interesting facts to baffle us with. For kick -off, Battery freezing- I understand that the high current draw on a 6V starting system will not allow the battery to lower it's specific gravity to the same extent as a 12 volt battery cranking system. The result is that there is less chance of freezing a 6V battery in service than a 12 volt battery. Is this true? Best regards Peter Toet
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