Months of meticulous planning has gone into this trip. We calculated weights at weigh bridges, obtaining certificates to prove maximum gross weight fully loaded, including individual axle weights. We had the vehicle serviced and gave the (trusted) garage free rein to replace anything that they thought might fail in the near future. The only issue that came out of that was the vehicle battery, which tested OK but occasionally failed to start the vehicle on cold mornings. That was replaced. Everything relating to the living space was also checked and double checked.
Within days of our arrival here in Spain, the leisure batteries started to lose their residual voltage too quickly, and were gassing excessively while under mains charge. Today I bit the bullet and replaced them.
This is not a difficult task, as they are located in open trays within the rear "garage", and are fitted with quick release terminal clips. Being wired in parallel it was also possible to replace them one at a time without disturbing the 12V supply line to the living quarters, such as the fridge controller, water heater, pump and lights.
I have decided to replace the old wet acid leisure batteries with Exide dual AGM's, sealed glass mat technology that means they are able to be mounted safely even on their side, with no need to have external gas venting - everything is contained within the battery. They are much safer in this type of use than wet batteries, but are also much more expensive to buy. They also have other advantages in that they are able to withstand longer dormant periods when the camper is not in use.
My choice here in Spain was a little limited. But, today we bought and installed a pair of Exide EP 450 dual AGM marine batteries. These are capable of being used for both engine cranking as well as the slower discharge over a period of time that happens when used to provide power to electrical equipment. This pair, linked in parallel are capable of providing 900 watt hours of power at 12V which I am confident should be ample for our intended use.
The job of replacing them is now complete, although I now have to find a way of safely disposing of the old batteries yet. I also took the opportunity of permanently wiring the C-Tek smart charger pigtails to the new battery bank utilising the second set of terminals provided which are threaded posts. Very convenient. The C-Tek is now connected on it's AGM setting for their initial charge before the solar panels again take over daytime charging, leaving the on board mains charger aside while we have the sun.
It is now time for afternoon drinks outside the van in the 27 degrees sun. Happy days!