When I was looking to buy a solar panel for the Defender, I wasn’t sure what size panel I would need to be able to maintain the auxiliary battery whilst it was powering the Engel MT45 fridge/freezer. After obtaining advice, I settled for the GB-Sol 85 watt semi-flexible solar panel. My primary aim was to have a system that would keep the fridge running for up to three days when the vehicle engine was not used to charge the battery.
As you can see in the above photos, the panel is glued to the roof of the Defender. Due to its very low profile, the panel is not visible to anyone standing next to the vehicle (great from a security perspective). The only give away is the gland fitting that accepts the cable from the panel.
Our recent stay in Salzburg allowed us to test the longevity of the auxiliary batter charge, without the solar panel recharging it. For a period of about 60 hours, the Defender was parked underneath a large tree that blocked any sunlight from reaching the panel. without the panel, I was concerned that the fridge would quickly deplete the auxiliary battery. Not so!
After 60 hours, the meter was down into the red warning range for the auxiliary battery, but there was still enough power to run the fridge – and that was with zero solar power over that same period. With the Engel fridge on the refrigerator setting (not freezer), it doesn’t seem to draw a lot of power. I therefore think that the aux Optima battery could probably get close to 72 hours of run-time by itself.
I am therefore confident that the 85 watt panel is large enough to extend the battery life well beyond 72 hours (provided the vehicle is not parked under a tree).