briand6868 wrote on Apr 3^rd, 2011 at 9:01pm:

Will it keep enough charge if left in the boot of the car, it would take up quite a bit of room in Ryanair cabin baggage, if o'dreary let you take it on board.

Mine is about 7 years old and will still start a car after several months after a full charge. They are available in Spain in the larger supermarkets etc. I don't think putting one in cabin baggage is a good idea though .