Nice to know the answer - thanks Smow.
Incidentally, a lot of the comments on battery life/charging go back to the days of dynamos (as opposed to alternators). They had a maximum output of about 23 amps and required the engine to be running quite fast to achieve this. With headlamps requiring about 10 amps, heater another 10 amps and maybe the wipers on as well, it was possible to drive in traffic with the battery having to provide some of the power. Then heated read windows arrived, requiring another 10 amps = trouble.
With the advent of alternators things changed - lots more amps available and, because of their construction, they could run at higher revs than a dynamo, so full power from them could be obtained at much lower engine revs.
Again, improvements in starting cut down the time the starter motor was running (taking several hundred amps), so batteries don't suffer the same discharge per start. (When did you last hear a car churning away at the starter for minutes on end). The "each start takes 20 mins driving to replace the charge" mantra dates back to the early days; nowadays it's unusual for a battery to be flat unless it's past its sell-by date or there's been abuse by the driver (lights left on etc).