Is this a bit dodgy?

Is that JW logged in as Russell?

Yes it's a bit dodgy but not necessarily catastrophic, the starter motor will be fine for short periods, you'll probably want to turn all the lights of to avoid blowing the bulbs, and maybe disconnect the feed to the regulator. I don't really know, I don't suppose there is much in the way of electronics in a 6v car,

Could you not tow start it with the other car?

No idea but I have a 6v charger you are more than welcome to if you wanted,

I can drop it round Sunday if needs be

No it's not me logged In as Russ

Also will you not risk toasting the alternator with a complete dead battery?

it might be ok , dont turn on any lights the coil might take the voltage the starting motor will spin much faster

when i used to banger race i used to temporarily link an extra 12 volt battery to give 24 volts just to start overheated/knackered engines

do 6 volt citreons have alternators james?

I know the starter will be ok, I've used a 6v one in a 12v car, I was more worried about the battery. Am I not, effectively, overcharging the battery by a massive margin? The car can't be tow started or bumped cos its got a trafficlutch. I jumped it off a 12v car earlier but there were some pretty big sparks off the battery and I must admit I thought it smelt a bit off. Would you jump a 12v car off a 24v truck? That sounds well dodgy to me, but is that ok too? Just out of curiosity now.

Russell,
copied and pasted, with the part you really need to know about highlighted;

I have jumped 6V cars many times with 12 V. I agree with turning off all the lights, radio and accessories. In addition, though, I pull off one lead from the 6V battery terminal and connect the jumper to the free lead. This eliminates the danger of battery explosion when current surges into the 6V battery.

Once the jumper is connected, turn on the ignition and quickly crank the car until it starts. Do not delay or the 12 V could damage the instruments. As soon as the engine starts, disconnect the jumper and jam the lead back onto the 6V battery terminal. If you're lucky, the engine will keep running through this transition (keep the revs up so it will run on the generator during brief time the battery lead is not connected) and you'll be on your way.


Fwiw, I used a similar technique when getting the Bijou which was sold to the Lane Motor Museum up and running.
Most of the fuel in the tank was about 5 years old and the thing just would not fire up, even with a new 6V battery.
It capitulated soon enough with 12v applied to the 6v starter and coil.

ken

Nice one Ken, that makes sense to me. Obvious when you think about it.

Personally I would be hesitant to do it, it would depend on how much I needed to start it.

So long as the 6v battery isn't completely flat, how about disconnecting the battery and other leads from the starter and holding them together with a molegrip, then connecting the jumplead directly to the starter terminal. That way it's only the starter motor that's got 12v on it. So long as the molegrips weren't going to short on the gearbox, it should be fine to disconnect the jump leads and drive the car like that.

Yes, we do that at work for stubborn motors that need to be moved without any further mucking about - it can blow a few fuses though, not necessarily the 'normal' stuff, but occasionally the police equipment - since they're coming into the workshops anyway, that's fair enough...