In short: Marine Electric Systems refit the electrical system of Explorado, a Nordhavn 55 trawler, between July and September 2025. We installed a 1,840Ah (about 47 kWh) house bank of eight Epoch 24V 230Ah LiFePO4 batteries, two 230V Victron Quattro 24/5000 inverter/chargers in parallel feeding a Victron autotransformer that turns their single-phase output into 120/240V split-phase, a Victron Skylla-i 24/100 charger, an ARCO Zeus alternator regulator integrated with a Victron Cerbo GX, and Victron Orion-Tr Smart DC-DC chargers for every start battery. We also rebuilt the pilothouse navigation station and replaced the satellite domes and antenna farm on the exhaust stack with Starlink, a satellite compass, and a weather sensor.

Key takeaways

• 47 kWh of 24V lithium. Eight Epoch 24V 230Ah batteries in parallel give 1,840Ah at 25.6V, each with its own 300A Class T fuse.
• 10,000 VA of inverter power, delivered as 120/240V. Two paralleled 230V Victron Quattro 24/5000s produce single-phase 230V. A Victron autotransformer creates the neutral that turns it into 120/240V split-phase, so the master cabin air conditioning now runs on inverter.
• Every charge source on one system. Shore, generator, Skylla-i, solar, and the ARCO Zeus-regulated alternator all charge to the same lithium targets and report to a Cerbo GX and GX Touch 70.
• Isolated start batteries. Orion-Tr Smart DC-DC chargers keep the main engine, wing engine, and 12V batteries charged from the house bank.
• A modern pilothouse. New flush-mounted displays, a new NMEA 2000 backbone, Starlink, and a decluttered exhaust stack.

Project details

The system at a glance

Why a 24V lithium battery bank on a Nordhavn 55

A Nordhavn 55 is built to cross oceans, and its electrical system runs the galley, the air conditioning, the watermaker, and every screen at the helm. Explorado is a 24V boat, and at this scale that matters. Twice the voltage means half the current for the same power, so cables, fuses, and switchgear can carry big inverter loads without oversized copper. We kept the boat at 24V and replaced the old house bank with eight Epoch 24V 230Ah V2 Elite batteries in parallel. Each battery is rated 5,888Wh, so the bank holds roughly 47 kWh, and because lithium iron phosphate can be used much more deeply than lead-acid, far more of that energy is actually available at anchor.

The house bank, inverters, and main DC distribution all live in Explorado's lazarette. The batteries sit where the old bank lived, but nothing else about the installation was reused. We removed the old cleating, fabricated new cleats and straps for every battery, and built an additional tie-down system in the port-side compartment so the bank stays put in a seaway. Every battery is labeled with its number and serial, which makes warranty tracking and troubleshooting simple years from now.

How to wire eight lithium batteries in parallel

Eight batteries in parallel only share the work evenly if every battery sees the same resistance. Each battery connects to the system through its own length-matched 2/0 tinned copper cables: negatives to a 600A bus bar, positives to a dedicated fuse.

On the positive side we fabricated a fuse block from eight 300A Class T fuses and custom copper bus, so every battery has its own high-interrupt fuse right at the bank. A large lithium bank can deliver enormous fault current, and Class T fuses are built to stop it. From the fuse block, two 4/0 cables run to an EGIS 600A heavy-duty battery switch, and two more 4/0 cables carry power to the DC distribution.

On the negative side, the 600A bus feeds a Victron SmartShunt 1000A through two 4/0 cables, and two more 4/0 cables run from the shunt to the vessel's DC negative. The shunt counts every amp-hour in and out of the bank, monitors the start battery voltage through a fused sense lead, and reports to the Cerbo GX over VE.Direct. We also fabricated a clear acrylic cover for the negative bus and shunt so nobody can accidentally bridge them, while the connections stay visible for inspection.

Twin Victron Quattro 24/5000 inverter/chargers with a split-phase autotransformer

The old setup used a single inverter/charger plus a 120V load-balancing transformer and bypass breakers. All of it came out. In its place we installed two 230V Victron Quattro 24/5000 inverter/chargers, labeled Master and Slave, programmed to run in parallel for 10,000 VA of combined capacity.

Why the autotransformer is needed

A 230V Quattro is a single-phase inverter/charger. When it inverts, its output is one line and one neutral at 230V, so on its own it cannot supply the separate 120V legs of a North American 120/240V split-phase panel. Paralleling two Quattros doubles the power, but the output is still single-phase 230V.

The Victron split-phase autotransformer, installed in the old inverter location, solves that. The Quattros' 230V output feeds the autotransformer, which creates a new center-tap neutral and delivers 120/240V split-phase to the boat's AC panel. The 120V circuits on both legs, and the 240V loads across them, all run on inverter. The autotransformer also balances 120V loads between the two legs, within its leg-to-leg rating, so the panel stays usable when one side is loaded more heavily than the other.

On shore power or generator, both 240V legs feed the Quattro AC inputs, the Quattros pass that power through to the autotransformer, and the same split-phase output keeps the panel running while the Quattros charge the batteries. A 16/2 control cable from the master Quattro's ground-relay terminal to the autotransformer means the neutral-to-ground bond is made in the autotransformer only when the Quattros are the power source, the way ABYC requires.

Paralleled Quattros need their AC wiring to be as symmetrical as their DC wiring. We installed two 65A terminal strips in a labeled junction box. One splits the incoming 240V shore or generator power to both Quattros through three #6 circuits each, all cut to the same length. The other collects both Quattro outputs and sends them to the autotransformer, which feeds the 120/240V panel through four #6 circuits. Each Quattro connects to the DC system through two 4/0 positive and two 4/0 negative cables.

We updated firmware on both units, programmed them to the Epoch charge profile, and linked them to the Cerbo GX over VE.Bus. Two new cooling fans in the Quattro compartment are wired to the master Quattro's programmable relay, so they switch on automatically when the inverters are working hard. For more on sizing inverter/chargers, see our guide on how to choose a Victron MultiPlus or MultiPlus-II inverter/charger.

Running air conditioning on inverter

Before the refit, the master cabin air conditioning and the AC pump could only run on shore power. We separated those circuits from the shore-only side of the panel and fed them from the autotransformer output, so the master cabin can stay cool at anchor without starting the generator.

Charging sources: Skylla-i, ARCO Zeus alternator regulator, solar, and Orion DC-DC chargers

A 47 kWh bank needs serious charging. On shore power or generator, the two Quattros are joined by a Victron Skylla-i 24/100 (3) charger, fed from spare 240V circuits and mounted on its own prepared bulkhead with a #8 case ground to the ship's ground. Its charge profile matches the Epochs, so it adds up to 100A at 24V whenever AC is available.

Alternator: ARCO Zeus replaces the Wakespeed

A lithium bank will take everything an alternator can give, so how the alternator is regulated matters as much as the alternator itself. We removed the boat's Wakespeed regulator and installed an ARCO Zeus high-energy regulator in its place, programmed to the Epoch charge profile. The Zeus is integrated into the Victron system, so alternator charging shows up on the Cerbo GX alongside shore power, the generator, and solar, and every charge source works toward the same battery targets.

Solar: three Victron SmartSolar MPPT 100/30 controllers

Explorado's solar panels feed three Victron SmartSolar MPPT 100/30 charge controllers mounted on the lazarette bulkhead, each labeled for the panel it serves. They charge the same 24V lithium house bank as every other source on board.

Start and 12V batteries: Orion-Tr Smart DC-DC chargers

The engine, wing engine, and 12V circuits each keep their own battery. Instead of tying them to the house bank, we installed a Victron Orion-Tr Smart DC-DC charger for each: a 24/24-17 for the main engine start battery, a 24/24-17 for the wing engine start battery, and a 24/12-30 for the 12V house battery. Each one has fused #8 input and output cables, a #8 ground to the ship's ground bus, updated firmware, and a charge profile matched to the battery it serves. A long night on the lithium bank can never leave the boat unable to start an engine.

The lazarette after the refit

Every DC positive circuit runs in split loom, every run is secured with saddles and ties, and every fuse, switch, and breaker is labeled. We also relocated the air compressor breaker to a new mounting pad under the aft stairs, built from marine-grade material, bonded with structural filler, and painted with bilge coat. On handover, the owner received a DC schematic of the new system and a walkthrough of how it all works.

Victron Cerbo GX and GX Touch 70 monitoring

A Victron Cerbo GX near the main panel, powered from a fused 24/7 circuit, ties everything together. The SmartShunt reports over VE.Direct, the Quattros over VE.Bus, and the ARCO Zeus regulator brings the alternator into the same network. The GX Touch 70 display shows the whole boat on one screen: shore and generator power, alternator charging, inverter status, AC and DC loads, and the state of charge of the house bank. The Cerbo also has its own cutout in the rebuilt nav panel. To learn more, read our guide on why every boater needs a Victron Cerbo GX.

Nordhavn 55 pilothouse and navigation station rebuild

The electrical refit was only half the project. The pilothouse was full of abandoned cable and equipment from years of upgrades, and the nav panel no longer fit the electronics the owner wanted.

We planed the large nav panel down to 1/2 inch, cut a new starboard section from marine plywood, and fabricated black acrylic panels for every helm cutout. The engine controls were templated and relocated to allow a new upper helm monitor, which sits flush on a 1/4 inch acrylic spacer. A third display was added beside an existing screen, and we cut openings for the chain counter, bilge controls, switch bank, spotlight, autopilot switch, horn, three Furuno repeaters, two VHF radios, and the Cerbo GX.

Behind the panels, we removed large amounts of dead wiring, traced and labeled what remained, and replaced twist-cap connectors with marine heat-shrink butt connectors. A new NMEA 2000 backbone runs down the mast to the nav station, with the hub moved from the masthead to the mast base locker where it can actually be serviced. New Ethernet runs serve the mast, spreader, and forward-facing cameras, all tested for continuity, and HDMI and USB-C runs link the helm to the nav station cabinet.

Starlink, satellite compass, and antenna upgrade on the exhaust stack

The exhaust stack carried two large satellite domes and a crowded antenna farm. We lowered the domes to deck level, removed the old antennas, and cut the antenna farm structure free. The stack now carries a new 360-degree anchor light with photocell on a custom bracket, a satellite compass on the port wing, a weather sensor beside it, and Starlink on a Star Mount Voyager mount on the stack wing, bedded watertight with a clear view of the sky. New cables were pulled down the mast on messenger lines, and abandoned wiring was removed. The AIS antenna got a soldered RG213 termination and a Simrad NSPL-500 VHF/AIS antenna splitter, so one antenna serves both the VHF and the AIS.

Lessons from this Nordhavn 55 refit

1. Fuse every battery in a parallel bank. With eight lithium batteries in parallel, one Class T fuse per battery protects against a fault inside any single battery or its cable.
2. Match every cable length. Equal-length 2/0 cables on the batteries and equal-length #6 AC circuits on the Quattros keep current sharing balanced.
3. 230V inverters need an autotransformer for a 120/240V boat. A 230V Quattro inverts single-phase. The autotransformer creates the neutral for 120/240V split-phase, which is what puts the 120V circuits and the air conditioning on inverter.
4. Bring the alternator into the system. An ARCO Zeus regulator integrated with the Cerbo GX means alternator charging is visible and managed like every other source.
5. Keep start batteries separate. DC-DC chargers protect engine starting no matter how hard the house bank is used.
6. Clean up before you add. Removing dead cable and old antennas made room for new electronics and made the boat far easier to troubleshoot.

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Frequently asked questions

How much battery capacity does the Nordhavn 55 Explorado have after the refit?

The house bank is eight Epoch 24V 230Ah LiFePO4 batteries in parallel, for 1,840Ah at 25.6V. That is about 47 kWh of stored energy.

Why use a 24V system on a large trawler?

At 24V, the same power needs half the current of a 12V system. That keeps cable, fuse, and switch sizes manageable while two 5,000 VA inverters and large charge sources run from the same bank.

Do Victron Quattro inverter/chargers produce split-phase power?

No. A 230V Victron Quattro produces single-phase 230V when inverting, and paralleling two units adds power but keeps the output single-phase. To supply a 120/240V split-phase panel, the Quattro output feeds a Victron autotransformer, which creates the neutral and delivers both 120V legs and 240V.

How does Explorado get 120/240V on inverter?

Two 230V Quattro 24/5000 units run in parallel for 10,000 VA of single-phase 230V. Their output feeds a Victron split-phase autotransformer, which creates a new neutral and supplies 120/240V to the AC panel, so both 120V legs and the 240V loads run from the lithium bank.

What does a Victron autotransformer do on a boat?

A Victron autotransformer creates a 120V neutral from a single-phase 230/240V supply, so 230V inverters or a 240V shore feed can power a 120/240V split-phase panel. It also balances 120V loads between the legs within its rating, and with its ground relay controlled by the inverter, the neutral-to-ground bond is made only when the inverter is the power source.

Can you run air conditioning on inverter on a Nordhavn?

Yes, with enough inverter capacity and battery. On Explorado, the master cabin air conditioning and its AC pump now run from the paralleled Quattros through the autotransformer, powered by the 47 kWh lithium bank.

Why does each lithium battery have its own Class T fuse?

Large lithium banks can deliver very high fault current. A 300A Class T fuse on every battery isolates a fault in any one battery or cable without taking down the rest of the bank.

How is the alternator regulated with a lithium bank?

On Explorado, an ARCO Zeus high-energy regulator replaced the original Wakespeed. It is programmed to the Epoch charge profile and integrated with the Victron Cerbo GX, so alternator charging is managed and displayed alongside every other charge source.

How are the engine start batteries charged from a lithium house bank?

Victron Orion-Tr Smart DC-DC chargers charge the main engine and wing engine start batteries, and a third charges the 12V house battery. Each is fused and programmed to the profile of the battery it serves.

Can Starlink be installed on a Nordhavn?

Yes. On Explorado we installed Starlink on a Star Mount Voyager mount on the exhaust stack wing, with the cable routed down the mast to the nav station and a clear view of the sky.

How long did the Nordhavn 55 refit take?

The work ran from late July to mid-September 2025, covering the lithium and Victron installation in the lazarette, the pilothouse and nav station rebuild, and the antenna and Starlink work on the exhaust stack.

Related projects

• Nordhavn 76 inverter/charger upgrade: twin Victron MultiPlus-II units on M/V Trixie
• Catamaran electrical upgrade: dual Victron Quattros and 1,840Ah Epoch lithium
• Leopard 48 lithium refit with dual Quattros and a Victron autotransformer
• Beneteau Oceanis 45 lithium refit with a Victron Quattro 5000W

Planning a lithium refit or an electronics upgrade on your own Nordhavn or cruising trawler? Get in touch with our Annapolis shop. Marine Electric Systems is an ABYC-certified marine electrical contractor at Bert Jabin's Yacht Yard in Annapolis, Maryland, and we design and install Victron and lithium systems throughout the Chesapeake Bay region. You can also browse the full Victron Energy range and Epoch lithium batteries in our online store.