[skidlids]

A caravan battery will probably give you the longest periods between charges, providing you are sensible with the loading and every so often you will have to drag it back to the house to charge it.
A suitcase style generator is a good option, we use a very quiet one at the race meetings, cost a bit more than the likes of the B&Q type gennys, but paying more gets you quality as well as quieter running. Honda are a popular choice, can also then use a drill etc and only need to carry a petrol can every so often