when we did my sons van we ran 12 batteries (cant remember what type) @ roughly $400.00 Oz dollars each (close enough to 3 thou GBP?) with a double inverter system to power our 10 amp 2 group compact espresso machine and grinder, and an electric booster pump (until it failed and we simply allowed the pump in the machine to do the job. Nothing else was powered (milk and other stuff were in an expensive cooler) You try NEVER run them down past say 2/3 discharge....and 1/2 discharge would be better and then you go charge up. It was easy in the van because he would do a morning shift then go home in the middle of the day, leave the van on charge for a few hours and go surfing, then go out again in the evening. Charging off a household power outlet is the cheapest form of charge, over here. If you run the batteries down too far they dont last long. If you end up with batteries with disproportionate capacity ( some weaker than others), the stronger ones are pulled down to the weakest...so when you replace them, you should replace them all together or you are forever chasing your tail. For what my son was doing, he probably would have benefited (in the long run) by going with 16 batteries instead of the original 12. The cost of a bank of batteries is not all that much different to buying a REAL generator set (rather than an el cheapo pretend generater), only the inverter/battery bank will if managed well, not have the ongoing cost of sticking diesel or petrol in the tank as a genie does. Thats only the batteries however. there is also the cost of the inverter system and professional fit up which can be considerable. On a cost benefit analysis bwteen an inverter VS genie system over a period of years, the inverter system will end up about the same (or cheaper if you look after it) except you pay all the money up front, where as with a genie you keep paying out for fuel (always rising) and service...... Consider also inverter system and batteries are silent and dont produce exhaust to pipe away. Do it right first up (ie pay the ransom) no matter which way you jump, and reap the benefit long term. Do it on a shoestring, and forever chase your tail around continually bleeding out hard earned money. This is particularly salient for anyone considering the purchase of an el cheapo generator set. Hope that helps.
