I do not use solar panels at all.........this is one of the systems I utilise that you could consider.
I use a 600 watt pure sine wave inverter and fit this to the towing vehicle battery under the bonnet with crocodile clips.
Make sure the placement of the inverter does not interfere with running the engine.
I have made a mains cable that is long enough to connect the inverter to the normal caravan mains connection.
With all mains appliances off in the caravan turn on the inverter and the normal caravan charger........this will charge the caravan battery.
The voltage of the vehicle battery must be monitored and the engine run on tick over if it falls to around 12.1 volts.
I especially carry out this charging sequence if I know I will be taking the vehicle for a trip off the campsite.
This charging can be done without the engine running as long as the displayed vehicle battery voltage remains above 12.1....there will then be enough left in the vehicle battery to start the engine.
I use this inverter and this
plug in battery voltage meter
I have obtained a 500 watt mains hairdrier which my wife uses as normal in the caravan using the above setup but with everything else turned off (including the charger)
Low wattage mains hairdriers are hard to find but vintage ones can still be found
......
here is one