Jayco has shown itself as a pioneer in technology and nowadays equips its vans with two very sophisticated Battery management systems that work in tandem and are not very well documented and very tricky to understand. As a matter of fact I am not sure that this does not cause some conflict or downside and Jayco is not very inclined to discuss their system which they say performs to their proprietary specification.

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. 

Problems

(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.

I'm still struggling with Jaycos charge system. It's very sophisticated, but poorly documented. It does not charge enough from the vehicles charge system (fused with 30A / 50A) !

It appears Jayco has wired in two AUX charge systems and possibly they are in conflict with each other. The JHUB tablet may put out values from the J35C controller (BMPRO) that are misleading, because it would not know that a competing charge circuit is in place.

The BMPRO AUX input is wired up comparatively thin, which could result in detecting an OFF state falsely (input dropping under the threshold voltage. SETEC recommends installing a mini boost ! Alternatively we could of course disconnect or ground the AUX input of the J35 and AUX charge only through the Redarc system. Downside is that we will miss out on the tablet being able to assess the system status properly ! Jayco has not properly document its system wiring for the FD19. Questions to Jayco about this topic have so far been ignored. If the AUX charge circuits are in conflict, solar charge capabilities are likely to show deficiencies as well.

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Battery charging from the vehicle is wired up to two charge circuits:

1) The Redarc intelligent solenoid based battery isolator
2) The Setec BMPRO J35C

To find them and their fuses you need to look in two places (compartments)

1) Under the bed
2) Under the floor mat behind the driver seat 

See conversation with SETEC for more details ...