In the old days – I'm talking about the 30s, 40s and 50s here – cars came equipped with a six-volt electrical system.  That's all they needed.  The engines were small – a hundred horsepower, or so – and they had few accessories – a starter (you had to crank the old Model T by hand), windshield wipers, a cigarette lighter and, if you were in tall cotton, an AM radio. 

As cars got bigger and more powerful and loa…