Charging a leisure battery from a car

[Andy Hunt]

Right a bit of an odd question here probably, but if anyone can help (adam2 are you out there?!) I'd be very grateful!

What I really want to do is to be able to charge a leisure battery (or two together) by running jump leads from a car battery (whilst still in the car) and running the car engine so that the alternator is going.

What I am wondering is:-

- what kind of current I would get from the alternator to charge the batteries?
- are there any other ways of recharging batteries using some kind of small petrol- or diesel-powered generator (or fuel cell even?) designed for the specific purpose?

Any help appreciated!!

[adam2]

Yes it is possible to charge batteries from a car electrical system by means of jump leads, presuming that the vehicle battery is fully charged, then the entire alternator output of typicly 70 amps is available.

I dont much like the idea though on account of the risks of mis connection, leads working loose from vibration etc.

Purpose made petrol driven battery chargers are available and would make better use of fuel than running a car engine for the purpose.
http://www.the12voltshop.co.uk/Shop/ind ... t_id=30185
Is one such unit.
Larger ones exist though I cant find a link.

I have also seen home made petrol driven battery chargers, generally consisting of a moped engine and a heavy duty 150 amp alternator.

Fuel cells for battery charging do exist but are still too expensive for general use, they generally require methanol fuel.
http://www.powerswitch.org.uk/forum/vie ... php?t=7881
FUEL CELLS.