Leon lcb11211@swbelldotnet wrote in news:YPydndGe9p2PjuzFnZ2dnUU7-
:

Cars used to have 6 volt systems but switched to 12 volt so that the
cables could be smaller.

Sort of. The real reason it was done was because tetra-ethyl
lead was invented.

(Tetra-ethyl lead allows higher octane gasoline. Higher octane
gasoline allows higher compression engines. Higher compression
engines require more power from the starter motor to get them
started, which requires more current from the battery. During
the 1950's compression ratios went from ~6:1 to ~9:1, which
became a problem for both the battery and the cables. Hence
the switch to 12 volt electrical systems.)

John