Took delivery of our 2022 378MBS-R at the end of February and started on the upgrades. Wanted to install two BattleBorn GC3 batteries and full Victron system without taking up any storage space as we full time and I knew GD often hide usable space. Unscrewed the wall panel in the passthrough area to find what I have to work with. Lots of space in there once I did some GD cable management, added a 2x2 frame and 1/2 ply backing panel on the rear of the outdoor kitchen wall that would be used to mount the Victron gear, and built a new small wall at the rear of the new space. Then moved the central vacuum back and 120V outlet into the new wall. Had GD send me some storage bay felt to finish new panels off same as the rest of the storage bay. Kept the old converter just in case it’s ever needed in the future and mounted it out of the way.
Spent quite a while fishing a pull cord from the storage bay, under the midbunk floor and up inside the kitchen wall to the control panel area. I was then able to pull wires in either direction for Surge Guard remote, SeeLevel display, and Touch50 display. Installed a USB in there too.
I wired the solar breaker box, solar chargers, Lynx Distributor, SmartShunt, BlueSea class T fuse & cutoff switches, Cerbo GX and Multiplus II onto the backing panel outside on the work bench. Was able to hide most cabling behind the panel so it’s a pretty clean install. The 4/0 cable are the only ones not hidden. Was able to manoeuvre the panel and gear into the storage bay and screwed it all into place.
FYI - the “roof satellite access channel hole” is nowhere near the interior of the wall that the cable is supposed to go into, it’s probably 12” away. Thanks Grand Design, if you are giving us a roof access channel, the top and bottom holes and pull string need actually be lined up!!!!! So I resealed the small GD hole panel back up and after some research decided to drill a new 2” hole next to the tanks vent stack and mount my roof access box there. 2 pairs of 10 gauge solar cable came down easily exactly where I expected them to be near the water heater.
So far the system is running really well. Have tested solar, AC and DC systems and happy with the results. SoftStart coming this week which will get wired into the bedroom AC and a ducted 12v fan system is going to get installed by the batteries and inverter to provide airflow while boondocking.
I really wanted to share my experiences with everyone who is thinking of tackling such a project but worried that they will loose storage space or have to add weight to the front bay. I was able to use 100% otherwise hidden wasted space, and also move the weight of batteries and Victron gear back nearer the axles. Both of which were my 2 main goals where the system was located.




Spent quite a while fishing a pull cord from the storage bay, under the midbunk floor and up inside the kitchen wall to the control panel area. I was then able to pull wires in either direction for Surge Guard remote, SeeLevel display, and Touch50 display. Installed a USB in there too.
I wired the solar breaker box, solar chargers, Lynx Distributor, SmartShunt, BlueSea class T fuse & cutoff switches, Cerbo GX and Multiplus II onto the backing panel outside on the work bench. Was able to hide most cabling behind the panel so it’s a pretty clean install. The 4/0 cable are the only ones not hidden. Was able to manoeuvre the panel and gear into the storage bay and screwed it all into place.
FYI - the “roof satellite access channel hole” is nowhere near the interior of the wall that the cable is supposed to go into, it’s probably 12” away. Thanks Grand Design, if you are giving us a roof access channel, the top and bottom holes and pull string need actually be lined up!!!!! So I resealed the small GD hole panel back up and after some research decided to drill a new 2” hole next to the tanks vent stack and mount my roof access box there. 2 pairs of 10 gauge solar cable came down easily exactly where I expected them to be near the water heater.
So far the system is running really well. Have tested solar, AC and DC systems and happy with the results. SoftStart coming this week which will get wired into the bedroom AC and a ducted 12v fan system is going to get installed by the batteries and inverter to provide airflow while boondocking.
I really wanted to share my experiences with everyone who is thinking of tackling such a project but worried that they will loose storage space or have to add weight to the front bay. I was able to use 100% otherwise hidden wasted space, and also move the weight of batteries and Victron gear back nearer the axles. Both of which were my 2 main goals where the system was located.



