Yes, your 12v appliances will still be powered from the leisure battery though - these are usually the lights and the water pump. Anything else you plug into 12v usually has to go through an inverter. Your fridge, if both EHU and gas can be powered on EHU (plugged in in the normal way, via a 3-pin plug socket. But because you are on EHU, you will be able to plug in a charger to charge your leisure battery!
You can't run a fridge on 12v unless on the move, towing - and your caravan charger is working ok. The fridge will either need EHU or gas to run on site.
Because of your situation, I would try it all without EHU (it is expensive) but see how you go for ten days without. Fridge on gas, use the 12v lights and water pump only when you have to, plus inverter for charging 12v items. You might just get away with it with the battery you are looking at. Make sure the battery dimensions are correct for the space it has to fit into! After approx 10 days, you will definitely need to recharge the battery, but this does depend on usage. If it gets too flat, it sometimes won't recharge at all, then its off to buy a new one.
A second 75-85 amp leisure battery would charge all your 12v items, as would a power pack for a week.
Another thing I thought about - if you are going to be working nights, and need to sleep during the day, see if you can arrange to be sited in a quiet corner. The kids will all be out on holiday soon, in season a caravan site isn't the quietest place to be - and a caravan doesn't keep much of the noise out!
Thanks for the replies but I've moved to another site that doesn't have extortionate electric prices. Doesn't the ehu charge the battery when hooked up then?
Yes the leisure battery gets charged up through the onboard caravan battery charger providing it is switched on and functioning. As you have little knowledge about 12 volt and 240 volt caravan electrics it may be good advice to purchase a caravanning book which will explain everything you need to know including generators, solar panels and just about everything else.
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