Maplin jumpstarter/charger/compressor/lamp/toaster is half price, £ 20.

or buy it on ebay for £ 25,

Could be the source of a small battery?
400 A cranking and whole unit is ~ 5 kg plus you could use the jump leads to wire up your car.



caveat: small batteries were discussed recently and the ones in similar units are GEL that are not designed forthis purpose, i.e. supplying big As to start and charging by alternator makes them unhappy

[Edited on 3/11/06 by 02GF74]

I've had a Clarke one for 7 years now and it still holds charge and starts my car or bike plus use as a camping battery. It will charge from the auxiliary socket in the car but not as much as via the power brick.