After much research, I have now purchased a solar panel and regulator for the vehicle. The main purpose of the solar panel is to maintain the charge in the leisure battery that runs the fridge/freezer when the vehicle is stationary.
Both of the Optima batteries will be charged via the alternator (using the X-Eng Charge split charging system) when the engine is running but the solar panel is required for the days when we are camping and the engine isn’t running.
The rigid glass solar panels are not well-suited to an overland vehicle whereas the semi-flexible panels are. They are very thin and can be glued to the roof of the vehicle, thereby minimising wind resistance and noise (and making theft of the panel very difficult). They are also lighter in weight. I initially planned to buy a 100 watt semi-flexible panel and found several such Chinese panels available on e-bay. Whilst much less expensive, I’m not convinced that the Chinese panels are of good quality. The power cables/wires on them seem to be very flimsy so I have doubts over their ability to stand up well to overlanding on top of a Land Rover. Due to quality concerns, I began to look at European panels that are made for the marine/boating market. These panels look to be much more sturdy and are designed to be weatherproof. They are also significantly more expensive than the Chinese panels and are not currently available in sizes larger than 70 watts.
After many hours of online research, I narrowed the search down to three brands of panels – Solara M-Series (made in Germany), Sunware (made in Germany) and GB-Sol (made in the UK). All three seem to have a good reputation. I found a couple of comparison tests that were done by boating magazines that compared a range of semi-flexible panels, including panels by my ‘final three’ manufacturers. The tests showed that the GB-Sol panel did as well as (if not better than) the Solara and Sunware panels. With the GB-Sol Flexi 70 watt panel costing as much as 250GBP less than its German counterparts. I decided that it was the best buy for me.
With the solar panel selected, I needed to also select a suitable controller/regulator. I knew that I wanted an MPPT regulator rather than the cheaper solar panel controllers. The MPPT regulators are able to capture and use more power from the panels than the standard controllers. Again, there are Chinese MPPT regulators that are very cheap but I have been advised not to cut corners on the regulator. The Morningstar Sunsaver 15A regulator has a strong reputation and is suitable for use with the GB-Sol panel and my Optima batteries.
I found that Midsummer Energy had both the GB-Sol Flexi panel and the Morningstar MPPT regulator listed at competetive prices. They also had the Morningstar Remote Monitor that is compatible with the Morningstar Sunsaver MPPT regulator. The monitor provides comprehensive system information for easy monitoring, including temperature, current and voltage. I contacted Midsummer Energy and received prompt and useful advice from Andy.
Andy told me that MPPT regulators are generally only connected to a single battery which, in my case, would be the secondary/leisure battery that runs the fridge. He also told me, however, that a voltage sensitive relay can be added that will allow excess power from the solar panel to be directed to the primary/starting battery whenever the secondary/leisure battery was fully charged. The relay doesn’t add much complexity to the system but can provide the opportunity to charge both batteries from the solar panel. I therefore decided to add the voltage sensitive relay into the package. The total cost for the package was about 800GBP. Certainly not cheap – but hopefully it will keep my fridge cold whilst we are camping, meaning fresh food and cold beers!