Here is a story new to me.

Danish mate heading for Copenhagen in his 2cv 1958 6 volt arrives at his hotel near Berlin with a flat battery. Dynamo dead with no spares or hope of repairs around Berlin. Here comes the interesting bit. Anders remove the 6 volt flat battery, stick a new 12 volt in. Fire up the 2cv and drive off. His thinking is that the starter will drain the battery to less than 12 volt allowing the coil to cope with maybe 10 volt or there about. Eventually the voltage will drop to 6 volt and futher below. When running out of voltage, Anders will buy another 12 volt battery and make it home to Copenhagen....
Is this clever thinking and how can the 6 volt coil cope. Starter, points, condenser, leads and plugs are not of any concern.

The starter will cope with no problem, as it was quite common to leave 6 volt starters in place when converting old VWs and Brit motors to 12 volts.

The coil is a different matter and it may overheat, pity he cannot find a car shop which could sell him a ballast resistor of about 2 ohms, or maybe an audio shop would have a power resistor of suitable value.

Alternatively, he could connect a headlamp bulb in series with the coil feed, but I'm not sure if its resistance would be too high.
Maybe worth a shot anway?

ken

Wonder when the coil gives up? Can't remember how to measure volt consumption on the plugs but how much driving can one do while the battery is dropping to 8 and 6 volt and so on. He told me that at one stage, the engine couldn't pull anymore in 3 gear but ok in 1st and 2nd. Berlin Copenhagen is 500 km, how many clicks before running out of juice.

Depends if he disconnects the brake lights, pretends he's driving a BMW/Volvo/large 4x4 and doesn't use his indicators...

ken

coil feed via the headlamps and the points set as wide as possible ?
or fit a 12v coil and continue to run it total loss

can cover good few 100 miles if your only running coil and brakelights

As opposed to coil, sidelights, brakeights and f**king 123 ignition!

Not that I'm still bitter or anything!

Cut the battery in half?







(joking of course..!!)

Also, you should understand that a 12 volt battery will still have almost 12 volts potential across its terminals, even when it's down to 10% charge.

State of Charge 12 Volt battery Volts per Cell
100% 12.7 2.12
90% 12.5 2.08
80% 12.42 2.07
70% 12.32 2.05
60% 12.20 2.03
50% 12.06 2.01
40% 11.9 1.98
30% 11.75 1.96
20% 11.58 1.93
10% 11.31 1.89
0 10.5 1.75

Link here, as the table doesn't copy easily...
Scroll down to 'state of charge'.
http://www.windsun.com/Batteries/Battery_FAQ.htm

With the correct voltage coil, a fully charged 45Ah battery should power the ignition for almost 15 hours. Starting on the handle or bump starting would help to conserve battery life as well.

ken

Buy a few of these and whack them in series: http://www.google.co.uk/imgres?q=6+volt ... 79&bih=609

Parallel, even?
ken