PHOENIXFLIER said:
After yet more research, and listening to the advice on here, I am giving up on the inverter idea. I am going to bite the bullet and get a "caravan" 12v TV and 80w solar panel with built in regulator. We only intend to use the TV for a few hours in the evenings (off grid), with probably one small light on. Brand new 110mah battery. TV rated at 2.5amps. Everything else will use gas.Comments welcome!
I'm still concerned that you chosen size of solar panel will not be enough.
Just to get an idea of the amount of current (Amps) you will use in a day you need to find the 12V current rating of each appliance and multiply it by the number of hours use it will have each day.
Just as a guide
Don't forget the lighting which if there not LED luminaries, then for each bulb or tube you can consider them to be using about 1A when on.
Modern fridges and water heaters also use some 12V current for their control systems and these can be considered to be about 0.25A on average each.
Car type radios can also consume 1 to 2 amps when being used and some even consume 0.1A when apparently turned off to retain memories.
Active television aerials also use some power Assume about 0.1A
Water pumps can often use 4 to 6A but generally do not run for very long and in reality the total power they use in a day is likely to be less then 1Ah
With out a TV its estimated that a 4 berth caravan will consume about 20 to 30Ah of battery capacity. But allowing for the inefficiency of recharging batteries, and the variable charge current due to the British weather, you need roughly 2.5x the solar panel capacity compared to the daily Ah usage.
With the addition of a TV at 2.5A used for about 4 hours a day equates to an additional 10Ah of battery usage.
So being a little pessimistic your total daily Ah usage could be the basic 30Ah + the 10 for the Tv giving 40Ah. that equates to a solar panel capabale of developing of about 100Ah of charge. Based on a 8 hours of effective daylight that is an average charge current of 12A rating Simple maths Volts x Amps = Watts (12A x 12V = 144Watts)
So I strongly recommend going for a minimum of a 120W or 150W panel.