The use of solar panels on caravans, motorhomes and camper trailers has increased over recent times due to the prices reducing in both panels and batteries. Those with sensitive ears might be jumping for joy as it means fewer generators humming away in those peaceful national parks or free camps. So what do you require to convert your accommodation to be self-sufficient? It is very easy to over-complicate the topic and before you know it you are arguing about what temperature is optimal to have your batteries at when charging them. Sure you could read books worth of information on the subject but does it need to be that hard?
For a basic solar setup you will need a battery or batteries, solar regulator, solar panels and wire/connectors. Sounds simple eh? Not so fast, the size or capacity of the setup depends on what needs to be run off it. In most basic setups the biggest consumer of your precious electrons will be your fridge particularly if you have a 2 way (12v and 240v). If you have a 3 way fridge and always use gas when parked up then you can probably get away with a fairly small setup.
Below is a quick lookup table based on other people’s experiences and using some simple maths in the background. Keep in mind this is a guide which hopefully will work for most caravans, it will get you close to what you are required. Obviously we can’t control how many cloudy days you get in a row. We generally plug into the car if we are free-camping and our batteries look like they are running a little low.
| Rough total usable capacity required (AH) | AGM (AH) | Li-Ion (AH) | Solar Wattage required | |
| Option 1: Medium/Large 2 way (12v) Fridge (average of 5amp draw), Lights, Water pump | 120-140 | 240 – 280 | 150-170 | 300-340 |
| Option 2: 3 Way Fridge running on gas when parked, Lights, Water pump | 25-30 | 50-60 | 30-40 | 60-75 |
| Additions (needed to be added to one of the above) | ||||
| TV – 3 hours a day | 15 | 30 | 18 | 40 |
| Laptop – 3 hours a day | 10 | 20 | 12 | 24 |
| CPAP (Medical) – 7 hours | 20 | 40 | 24 | 48 |
There are two types of solar regulators. PWM (Pulse Width Modulation) have been used for years in Solar systems, and are well established. They are simple and cost effective. The other option is Maximum Power Point Tracking (MPPT) controllers which allow panels to charge batteries at the optimal voltage all the time (a potential increase in charging efficiency up to 30%). Lots of DC/DC chargers will have a solar regulator in them and offer a solution to allow both the tow vehicle (via alternator) and the solar panels to charge the on-board batteries. Really which one of these you go depends on your budget and space. You will probably need the higher end of the panel range in the table below if going PWM.
Stay tuned – we’ll be covering off how to install these items into a van in the near future!