Solar and battery capacity required for cabins and RVs is usually limited. As with homes and properties, always have maximum solar capacity. Consider using LiFePO4 batteries as 80% of their nominal capacity is available. LiFePO4 batteries are also light and compact. Lead acid and AGMs, however, are fine for converted coaches. For those, size and weight are less critical.
The author’s 2004 4.2 litre TD Nissan Patrol and TVan each had their own self-contained solar system. Pic: rvbooks.com.au/
Cabins and RVs should have the maximum solar capacity feasible. This ensures batteries will charge fast and deeply even with intermittent sun. The battery capacity required for cabins and RVs needs to cope for about three days. From thereon it is cheaper to charge via a grid-voltage charger. This can also be powered via a small inverter/generator. See: RV Solar and Alternator Charging.
As a rough guide, (and assuming a 12-volt system) do not allow battery capacity (in amp hours) to exceed 50% of your solar capacity (in watts). Unless you do, your batteries may not adequately charge. A 100 amp-hour battery thus needs at least 200 watts solar capacity. Seemingly excess solar capacity will assist charging during times of little sun. There is no risk of overcharging. The solar regulator automatically prevents that.
Dual solar system
AGM batteries are ideal for cabins and converted coaches, but their 33 kg per 100 amp-hour (for 12-volt units) is too heavy for small travel trailers. Where size and weight are critical use lithium-iron LiFePO4 batteries. They cost more, but as 80% of their nominal capacity is available, that cancels out their higher price. LiFePO4 batteries are also light and compact. They are about one-third the size and weight of AGMs. Another benefit is that unlike conventional lead-acid batteries, as long as first fully charged. AGMs can be left for up to a year without use. LiFePO4s can be left for evem longer.
If towing a camper trailer or travel trailer consider haing a self-contained solar system in each. This enables you to have one (charging) in the sun. The other can be in shade. You can readily interconnect the systems to share power and battery capacity.
Having two self-contained systems enables you to have a small fridge in the tow vehicle. This is very convenient when shopping. That vehicle too, can have a solar array on a roof rack and an associated battery.
Our 4.2-litre Nissan Patrol and TVan (shown above) were set up this way. Each had its own system. Moreover, they could be used separately or paralleled if desired. In over seven years, however, we never needed to do so.
It is also feasible to have alternator charging. :outlines how.