Modern Caravans and Motorhomes come with a battery built in, These are called leisure batteries and are designed for long use between charges.
They will normally have a rating in Amp Hours. Typically a leisure battery will have a rating between 75 amp hours and 110 amp hours.
What do these figure mean in real terms?
If you have a 110 amp hour battery under perfect conditions you could run a single appliance that’s rated at 110 amps for 1 hour, now that does not seem much but lets do some maths:-
A typical caravan or motorhome light bulb is about 8 watts using the rule that AMPS = WATTS / VOLTS then 8 watts / 12 volts = 0.666 amps so if a light bulb is less than 1 amp we could run a single bulb for over 100 hours, of course that’s not a realistic calculation for the following reasons.
1. We don’t just use a single bulb, we also have water pumps, electric fans on our heaters and electric gadgets, all these things will place varying demands on the leisure battery
2. The battery in our vans is never perfectly charged or working under perfect conditions.
Given that you will most likely be running the fridge on gas and lights will be used a minimal amount in summer then you should be able to see that on a typical summer weekend outing you are very unlikely to run out of power.