Talking 6 Volts systems.

In the Netherlands my mum had a Renault 4 with a 6 Volts generator and accumulator. ( 70Ah)
I rememberr quite well the Ammeter on the dash was which was a VDO -50_0_+50 Amp meter. I drove the car around our farmhouse in the weekend while I was about 14 Years young.
After starting, especially in winter at -15°C. The starter motor, (demarreur) turned over so slow that it ground to a halt before every compression stroke of the engine. After say like 10 seconds very slow cranking the engine jumped into life. Ammeter off the scale for about 2 minutes and feeling warm to the touch when the load settled down to 30 Amps and tapering off to about 10 Amps in 5 minutes.

Silicon Chip had a very interesting article re the 42 systems in the cars of the future.
July 2000 issue, probably still copies available from the editor. Worth while reading.
a 36 Volts battery system is proposed with a DC - DC converter to provide 12 Volts for lamps and low power devices while electrically steppermotor driven camshafts and electrically driven turbochargers can be run from the 36 Volts supply.
12 Volts is still preferred for lamps because the filament is thicker and will generally last longer with vibrations from the vehicle in motion than a 36 Volts lamp.

The problem was also adressed with high tech cars like BMW 750iL series which use a 12 Volts 150 Amps watercooled alternator. to furnish the high loads from elecrically heated catalic converters etc.

Interesting times ahead for future cars [Linked Image]

The product of rotation, excitation and flux produces electricty.