The short version: we gave a Newmar Dutch Star 418 the full off-grid treatment: 1,000 watts of rooftop solar, a 1,200Ah lithium battery bank, a complete Victron power system in place of the factory Magnum inverter, a DC-DC charger in place of the factory battery isolator, and a soft start on the front air conditioner. The coach can now run its A/C, appliances and electronics from the battery bank, which makes it ready for boondocking and off-grid travel.

The Goal: Boondock a Big Class A on Battery Power

The owner wanted a coach that could camp off-grid in comfort, running the air conditioner and everything else from the batteries rather than leaning on the generator. That meant replacing the factory batteries and inverter, adding as much solar as the roof would hold, and keeping the generator’s automatic start working with the new system.

We did the job on-site at the customer’s location in Tucson over three days.

What We Installed

1,000 watts of rooftop solar (4× 250W panels)
1,200Ah Renogy lithium battery bank (4× 300Ah batteries)
Victron 12/3000/120 2×120V inverter/charger, replacing the factory Magnum inverter
Victron MPPT 150/70 solar charge controller
Victron Lynx Distributor and SmartShunt
Victron Cerbo GX and Touch 50 display
400A Class-T fuse and a BEP 400A battery disconnect
Victron Orion DC-DC charger, replacing the factory battery isolation manager (BIM)
SoftStart on the front rooftop air conditioner
Automatic generator start, re-integrated with the new system

The Roof: Working Around Girard Awnings

The Dutch Star’s Girard awnings look great, but their mounting feet and the fascia on the other side take up a lot of roof. With limited space, you either use the space you have or build a rack, and here we used the space we had: four 250W panels laid out to fit between the awning hardware.

The panels are wired as two pairs in series, front and back, and the two pairs are joined in parallel where the cables enter the roof. Newmar pre-wires these coaches for solar, so we tracked down the factory wiring and finished it off. The cables are secured under the panels and sealed where they meet the roof. The solar feed runs down in 6-gauge wire to a correctly sized DC breaker.

While we were up top, we installed a SoftStart on the front air conditioner so it can start and run from the battery bank through the inverter.

The Electrical System

We took out all the old batteries and the old battery tray, and put four 300Ah Renogy lithium batteries in the front battery compartment for 1,200Ah of storage. A new side panel holds the Victron gear. From the batteries, power runs through a 400A Class-T fuse and a BEP 400A disconnect into the Lynx Distributor, with the SmartShunt mounted level beside it, and from there to the inverter, the DC-DC charger, the solar controller and the coach’s 12V system.

One detail that matters: Newmar runs a bundle of negative DC cables down into that compartment. We moved them to the working side of the shunt so every amp going in and out of the batteries is counted. Leave them on the wrong side and the battery monitor shows the wrong state of charge.

The new Victron inverter/charger went in exactly where the factory Magnum was. Upstairs, the Touch 50 display replaced the Magnum remote in the same cabinet. The Cerbo GX lives in the front electrical compartment, with long data cables run back along the chase by the generator compartment to the shunt, the solar controller and the inverter.

We also replaced the old Magnum generator auto-start controller and ran a new auto-start cable, so the owner keeps automatic generator start from the dash.

Why Replace the Factory Battery Isolator With a DC-DC Charger?

Many motorhomes come with a battery isolation manager (BIM) that links the chassis and house batteries while the engine runs. That works for lead-acid batteries, but it gives no control over how hard the alternator charges a large lithium bank. We replaced the BIM on this coach with a Victron Orion DC-DC charger, wired to the original 12V on/off switch in the cab, so the house batteries charge from the engine at a known, controlled rate.

Can a Class A Run Its Air Conditioner on Lithium and Solar?

Yes, with the right system. This coach now runs its front air conditioner, appliances and electronics from the 1,200Ah battery bank through the Victron inverter. The SoftStart reduces the A/C’s start-up surge so the inverter can handle it, and the 1,000 watts of solar plus the DC-DC charger refill the batteries during the day and on the road. For heavier use, the generator still starts automatically when it’s needed.

Everything was installed by an ABYC Certified Electrician and Victron Certified technician.

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