We rebuilt our catamaran's entire 12V electrical system around two Victron Quattro 12/5000/220-120V inverter/chargers, four Epoch 460Ah 12V LiFePO4 batteries wired in parallel, and a Victron Cerbo GX with a GX Touch 70 display. The result is roughly 23.5 kWh of lithium storage, 10,000 VA of inverter capacity at 120/240V split-phase, and one screen that shows every watt moving through the boat.

This post walks through each part of the install with photos from the engine room and battery compartment, explains why we chose each component, and shares what we learned along the way.

Quick specs: the upgrade at a glance

Why we upgraded our catamaran's electrical system

A catamaran this size lives on its electrical system: refrigeration, watermaker, air conditioning, galley appliances, electronics, and a bow thruster all draw from the same house bank. We wanted a system sized for how we actually use the boat, with less generator time and a single place to see what is happening.

We wanted three things from the refit:

• Silent nights at anchor. Enough lithium capacity to run the boat overnight without the generator.
• Real AC power on inverter. Two 5,000 VA inverters so large loads like air conditioning and cooking can run from batteries.
• Every charging source working together. Shore power, generator, solar, and both engine alternators all feeding one well-managed bank.

From above you can see the solar array that feeds the new system: three panels across the stern arch and two on the coachroof. On a boat with this much deck area, solar is free energy every sunny day, and the new MPPT controller makes the most of it.

Two Victron Quattro 12/5000/220-120V inverter/chargers

The heart of the system is a pair of Victron Quattro 12/5000/220-120V units, labeled Quattro 1 and Quattro 2. Each one is a 5,000 VA pure sine wave inverter, a 220A battery charger, and an automatic transfer switch in a single box.

Why two Quattros instead of one larger unit:

• Split-phase 120/240V output. The two Quattros are configured for 120/240V split-phase at 60 Hz, with each unit running one leg (L1 and L2), matching the boat's dual-leg AC panel. The Touch 70 screen shows both legs independently.
• Two AC inputs per unit. Shore power and the generator each get their own input, and the Quattro switches between them automatically with 2 × 100A transfer capacity.
• PowerAssist. When shore power is limited, the Quattros top up the shortfall from the batteries instead of tripping the dock breaker.
• 440A of combined charging. Two 220A chargers refill a large lithium bank quickly from shore or generator.
• Redundancy. If one unit ever needs service, the other still powers its leg.

Each Quattro is fed through its own pair of 400A Class T fuses, and a 270 CFM blower keeps the compartment cool. Victron rates the Quattro for continuous duty, but heat is still the enemy of any inverter in a closed engine-room space.

The battery bank: four Epoch 460Ah 12V LiFePO4 batteries in parallel

We installed four Epoch Elite 460Ah 12V V2-T lithium iron phosphate (LiFePO4) batteries, wired in parallel for a single 1,840Ah house bank at 12V. At a nominal 12.8V that is about 23.5 kWh of stored energy.

Why lithium made sense for a cruising catamaran:

• Usable capacity. LiFePO4 can be discharged much deeper than lead-acid without damage, so far more of the 1,840Ah is actually available.
• Weight. Lithium is a fraction of the weight of an equivalent lead-acid bank, which matters on a catamaran where weight costs speed and load-carrying.
• Fast charging. Lithium accepts high charge currents, so the Quattros, alternators, and solar can refill the bank quickly.
• Steady voltage. Voltage stays flat through most of the discharge, so inverters and electronics see consistent power.

Every battery is labeled with its number and its September 2026 install date, which makes warranty tracking and future troubleshooting simple. The cables are run in split loom and secured along the compartment so nothing chafes when the boat is moving.

The wide view shows how the bank connects to everything else: the House remote battery switches and SmartSolar controller on the left, the main fuse bank on the right, and the cable runs that tie it together.

Charging sources: solar, alternators, and DC-DC chargers

A big lithium bank is only as good as the ways you can refill it. Beyond shore power and the generator (both through the Quattros), the boat now charges from solar and from both engine alternators.

Solar: Victron SmartSolar MPPT 150/100-Tr VE.Can

The solar array feeds a Victron SmartSolar MPPT 150/100-Tr VE.Can. It handles up to 150V from the panels and delivers up to 100A into the batteries. The VE.Can port connects it directly to the Cerbo GX, so solar charging follows the same battery-managed targets as every other charger on board.

Alternators: two ARCO Zeus high-energy regulators

Stock alternator regulators are designed for lead-acid batteries. With lithium, an unregulated alternator can run at full output for long periods and overheat. We installed two ARCO Zeus high-energy alternator regulators, one for each engine. They have NMEA 2000 and CAN bus (RJ45) connections, and the field, power, and sense wiring for each engine runs through a dedicated, labeled fuse block.

The wider shot shows how the regulators sit in the compartment, with their harnesses routed in loom down to the cable runs, the negative bus bar to the right, and Quattro 1 mounted alongside.

Start and thruster batteries: four Victron Orion XS 1400 DC-DC chargers

The engines, generator, and bow thruster each keep their own battery. Four Victron Orion XS 1400 DC-DC chargers, labeled Thruster, Port Engine, Stbd Engine, and Genset, keep those batteries topped up from the lithium house bank. Each delivers up to 50A, and each output has its own Blue Sea fuse holder. The whole group is protected by a 250A ANL fuse on the main fuse bank.

This approach keeps the starting batteries isolated, so a heavy night on the house bank never leaves us unable to start an engine or the generator.

Circuit protection and DC distribution

With 1,840Ah of lithium behind it, a dead short could deliver thousands of amps. Every major circuit on the boat now runs through a properly rated, clearly labeled fuse, and the house bank can be disconnected remotely.

Class T fuses have a very high interrupt rating, which is why we used them on the largest, highest-current circuits closest to the batteries. Two spare positions leave room for future additions.

Two EGIS remote battery switches, both labeled House RBS, can disconnect the house bank without crawling into the compartment, and their green status lights show at a glance that the bank is connected. A Blue Sea ML-RBS remote battery switch controls the separate Euro inverter/charger circuit. Between them, a Blue Sea fuse block feeds the small control circuits: 24-hour power, the field, power, and sense wires for each alternator regulator, the Euro RBS, and the Cerbo GX.

System control and monitoring: Victron Cerbo GX and GX Touch 70

The Victron Cerbo GX is the brain of the system, and the GX Touch 70 at the nav station is the window into it. The Cerbo talks to the Quattros, the SmartSolar controller, and the batteries, then coordinates charging so every source works toward the same target.

This screenshot was taken on shore power at 21:04, and it shows the whole boat at a glance:

The inverter/charger tile reads "External control," which means the Quattros are being managed by the GX system rather than running only on their own internal settings. That is exactly what you want with lithium. The Cerbo can also connect over Wi-Fi to Victron's VRM portal, which lets you check the system from a phone when you are off the boat.

Lessons from our lithium and Victron upgrade

If you are planning a similar marine electrical refit, these are the choices we would make again:

1. Label everything. Every fuse, charger, switch, and battery on our boat carries a printed label. It costs an afternoon and saves hours the first time something needs troubleshooting.
2. Use Class T fuses close to a lithium bank. Large LiFePO4 banks can deliver enormous fault current, and Class T fuses are built to interrupt it.
3. Regulate your alternators. Lithium will pull everything an alternator can give. External regulators like the ARCO Zeus protect the alternator from overheating.
4. Keep start batteries separate. DC-DC chargers keep the engines, generator, and thruster on their own batteries while still charging them from the house bank.
5. Plan for heat. Two 5,000 VA inverters in an enclosed space need forced ventilation.
6. Put monitoring where you will see it. A GX Touch 70 at the nav station turns the electrical system from a mystery into something you check like the weather.

Shop this system

Building something similar? These are the components from this install that we stock, plus fuses matched to the ratings on our fuse bank.

Frequently asked questions

How much battery capacity does the catamaran have after the upgrade?

The house bank is four Epoch 460Ah 12V LiFePO4 batteries in parallel, for 1,840Ah at 12V. That is about 23.5 kWh at a nominal 12.8V.

Why use two Victron Quattros instead of one inverter?

Two Victron Quattro 12/5000/220-120V units give 10,000 VA of combined inverter capacity, 120/240V split-phase output at 60 Hz on two legs, 440A of combined charging, and redundancy if one unit needs service.

Can a Victron Quattro charge lithium batteries?

Yes. The Quattro has configurable charge settings for lithium, and with a Cerbo GX it can be managed by the GX system, which the Touch 70 shows as "External control."

What does the Victron Cerbo GX do on a boat?

The Cerbo GX connects the Victron inverter/chargers, solar charge controller, and batteries into one system. It coordinates charging, logs data, and drives the GX Touch 70 display.

How do you charge lithium batteries from a boat's alternators?

We use an ARCO Zeus high-energy alternator regulator on each engine. It controls alternator output so it does not overheat while charging a lithium bank.

How are the engine start batteries charged?

Four Victron Orion XS 1400 DC-DC chargers charge the port engine, starboard engine, generator, and bow thruster batteries from the lithium house bank, at up to 50A each.

What fuses protect a large lithium battery bank?

The highest-current circuits use Class T fuses: 400A on each Quattro feed and 300A on each alternator. Smaller circuits such as the DC panel, bilge pumps, and DC-DC chargers use ANL fuses.