Using two independent battery management systems systems in tandem invites risks. There will be upsides and downsides for such complexities which are little understood by anybody including Jayco and its dealerships.
Smart Battery Isolators (SBI's)
For starters Jayco uses an SBI from Redarc which senses the voltage of the FIAT vehicle battery and the Jayco cabin house battery and connects the two batteries together whenever it senses that one of the batteries is getting charged. This system is invisible as it is undocumented and works in the background.
The Jhub Battery management System
Setec (BMPRO) is Jayco's supplier of the highly visible tablet monitored Jhub system. It is build in partnership and has been customised and designed to Jayco's specifications.
If you want to learn more about SBI's have a look at PowerStream products (Utah) as well as the Redarc system (Australia). The sales brochure can be found here.
(1) Both aux charge systems together perform rather poorly under driving conditions. I was referred to Setec, who suggested that I need to add their miniboost. Specs can be found here at https://teambmpro.com/wp-content/uploads/171102_M-MB2.pdf . Setec recommends a wire size of 5mm2+, which means we need at least 2.5mm for the diameter of the copper core !
(2) The Redarc system will boost the house battery with the vehicle battery for hours, because it senses both battery voltages, connects if any of it rises and only disconnects after it has noticed a big enough voltage drop on the closed contact, which means the vehicle battery gets dragged down to a discharge point of 12.6V ! Under sunshine conditions and in the absence of any high loads the car battery may get charged and discharged for hours.