Does anybody on here know what the ampere hour drain is when a 12 volt 2CV engine is running? No other drains involved, just the engine and no input from an alternator. I'm trying to work out running times on a battery alone, no charging system and no lights.

Brooky.

just the ignition& coil, and of course the strarting motor unless you used the starting handle
if the batterys new is a consideration
if its old well its conjecture
the battery will have the output& date of manifactuer printed on it,but if its not being charged its an uknown quantity
i might be wrong

Brooky,
it would depend on the primary resistance of the coil, if it's a standard 2CV coil with 3.5 ohms and say 50% dwell on the ignition, that would pull an average of just under 2 amps.

Stay away from the brake pedal (3.5 amps) and divide the rated amp-hours of your battery by 2, then 2 again to give you a reasonable factor of safety in the 'get you home' stakes.

Or carry another battery, but don't forget that running a standard battery right down will reduce its service life.
Maybe a leisure battery would be more suitable, as they're claimed to cope with deep discharge usage.

ken

Thanks Ken, that's excellent. I was thinking that a leisure battery might be a better option. The question was in fact, not actually concerning a 2CV but my 1934 Morgan three wheeler, which is running a 2CV coil. So your figures still apply. I'm intending to run it in 'stripped down racer style' with no lights (bar a brake light, oops!) and no mudguards. The car also has no starter motor so no enormous coil-robbing drain there either. Not really worried about the MOT situation as I soon won't need one. Happy days!

Brooky.

Brooky,
that sounds like great fun, I think a photograph or two may be requested.

With the benefit of a good night's sleep, a couple of ideas;
Fitting an led brake light would reduce its consumption to next to nothing.
Using a 'points assisted' ignition unit such as the Boyer Bransden ID or a Velleman kit would allow the use of slightly wider points gap/lower dwell, with reduced current draw for your ignition.

ken

Thanks Ken. Yes, I was aware of automotive LED bulbs but failed to make the connection in my brain that I could, in fact, use one! As to the CDI ignition systems, I must look into that as they seem stupidly cheap for quite a lot of benefit, apparently. I'll have to find a good hiding place for it though!

Brooky.

With such a low drain, I wouldn't worry too much about hurting your battery. What are the chances of you actually running it completely flat each time anyway?!

Surely you'd get the best part of 20+ hours running given Ken's figures - ain't that enough (or are you going for endurance racing... )

http://www.mmbalmainauto.com.au/PDF/Sta ... teries.pdf

The problem is that unless the battery voltage/state of charge is monitored accurately, it's very easy to run it virtually flat, with the consequence being much reduced service life.

ken

Crikey Ken, I never realised there was so little 'indicated voltage' difference between a fully charged battery and a flat one. I guess I shall need to add a voltmeter to the dashboard. That's ok, I can put it where the light switch won't be! I'm not planning on 20+ hour journeys but I will be carrying a spare, fully charged battery and both will be leisure batteries. Not a problem as I work on a caravan holiday park with a well-stocked accessory shop!

Brooky.

Brooky

Marine battery's tend to have a bit more grunt. Maybe worth a thought ?