Leopard 48 Catamaran Lithium Battery Refit: A 1,840 Ah Epoch House Bank, Dual Victron Quattro 5000W, and a Complete Electrical Overhaul on Tortuga

When a 2016 Leopard 48 sailing catamaran is being prepared for serious cruising, the electrical system has to keep up — and on most factory builds, it does not. Tortuga's refit replaced the entire DC and AC backbone with a fully integrated lithium platform: a 1,840 Ah Epoch house bank, two paralleled Victron Quattro 5,000W inverter-chargers, a 100 A Victron Auto Transformer for 120/240V balancing, externally regulated alternators on each engine, and a unified Victron Cerbo GX network tying every charge source and load into one monitorable system.

The system at a glance

• Vessel: 2016 Leopard 48 sailing catamaran Tortuga (Alexandria, VA)
• House bank: 4 × Epoch 12V 460Ah V2 LiFePO₄ batteries — 1,840 Ah at 12V
• Inverter/charger: 2 × Victron Quattro 12V / 5,000W (paralleled — 10 kW total)
• AC balancing: Victron Auto Transformer 120/240V / 100A
• Shore power: 50A / 125-250V SmartPlug inlet, 50A GFI breaker, 6/3 marine cable
• Galvanic protection: ProMariner ProSafe FS60 60 A galvanic isolator
• DC distribution: Pair of 500 A EGIS battery switches, 600 A tinned-copper bus bars, fully labelled Class-T and ANL fuse block
• Alternators: Externally regulated per engine, 500 A shunts on each output
• Regulators: Arco Zeus on port and starboard engines
• DC-DC charging: Dedicated DC-DC chargers per engine start battery
• Generator: Northern Lights, reconfigured from 50 Hz to 60 Hz at ~1,800 RPM
• Solar: Existing array integrated via Victron MPPT charge controller
• Monitoring: Victron Cerbo GX with Touch display
• AC panel: Blue Sea Systems with double-pole breakers; fully inverter-capable distribution

Why a lithium refit on a Leopard 48

Production catamarans like the Leopard 48 leave the factory wired for shore power and short hops between marinas. The original AGM bank was reliable but offered roughly half its rated capacity in usable terms, slowed dramatically above 80% state of charge, and gave the crew no real-time visibility into what each charge source was doing. For a cruising owner who wanted long anchorages, an active watermaker, and far less generator runtime, lithium was the right answer — provided every charge source on the boat was rebuilt around it.

The 1,840 Ah Epoch lithium house bank

Four Epoch 12V 460Ah V2 LiFePO₄ batteries were installed in parallel in the cockpit battery compartment, replacing the four AGMs that came out. Each battery was strapped down with approved restraints to eliminate movement under sail, and every primary cable was routed vertically through watertight cable glands sourced from McMaster-Carr to keep the run clean and serviceable.

Length-matched cabling runs from each battery's terminals to a 600 A tinned-copper bus bar, ensuring balanced charge and discharge across all four batteries — critical for parallel banks of this scale. Epoch's inter-battery communication cables were daisy-chained between units, with the system display mounted in the port hull electrical cabinet for quick state-of-charge checks. Ethernet runs from the bank carry battery telemetry to the Victron Cerbo GX. Insulated boots cover every terminal, and chafe protection wraps every conductor.

DC primary distribution: dual 500 A EGIS switches and a Class-T fuse block built for the load

A 1,840 Ah lithium bank doesn't just need bigger cables — it needs a primary distribution architecture that can handle the current and isolate faults cleanly. We installed a pair of 500 A EGIS battery switches in the port hull electrical cabinet, splitting the load between them, with double 4/0 AWG cable runs from the battery distribution through the EGIS switches and onward to the Quattros via the new fuse block.

The fuse distribution block was fabricated from labelled Class-T and ANL fuses sized for each circuit: 400 A Class-T fuses for each Quattro 5K, 250 A ANL fuses for the port and starboard alternator outputs, and ANL fuses for the DC panel, watermaker, amplifier, and Centaur charger circuits. Existing fusing, abandoned cabling, and obsolete bus bars were stripped out before the new components went in, freeing space and improving service access throughout the cabinet.

Dual Victron Quattro 5,000W inverter-chargers with a 100 A Auto Transformer

The original inverter and charger came out and were replaced with two Victron Quattro 12V / 5,000W inverter-chargers, mounted side-by-side in the primary electrical cabinet and positioned forward to leave room aft for the new DC distribution and double 4/0 cabling. A dedicated ventilation fan circulates air around the units, improving thermal performance under sustained load while keeping cabin noise low.

To handle the catamaran's 120/240V split-phase AC system on a 50 A shore connection, a Victron Auto Transformer 120/240V 100 A was glassed into a plywood pad behind the helm, with wiring routed downstream of the Quattros. The autotransformer balances 120V branch loads automatically across the 240V supply — preventing leg imbalance from tripping the main breaker when one side of the boat is loaded more heavily than the other.

Shore power: a proper 50 A inlet, GFI protection, and galvanic isolation

The original 30 A shore inlet was replaced with a SmartPlug 50A / 125-250V inlet — a step up in both capacity and connection reliability over the legacy twist-lock standard.

Per ABYC requirements, a 50 A GFI shore power breaker was installed in an enclosure box in the aft stern locker, within 10 feet of the inlet, fed by 6/3 marine-grade cable to the Quattros' AC input. A ProMariner ProSafe FS60 60 A galvanic isolator was added to the AC ground path to protect the boat's underwater hardware from stray-current corrosion at marinas — essential on a catamaran with two saildrives sharing a marina ground.

Alternators: external regulation per engine, fully integrated

Both factory alternators were removed, reconfigured for external regulation, and reinstalled with output cabling re-evaluated and upgraded where ampacity demanded. The original battery combiners were pulled, and that cable was repurposed to feed the alternator output directly into the lithium house bank — exactly where the energy needs to go.

Each engine got its own Arco Zeus alternator regulator, with full sensor harnesses and Ethernet runs back to the Cerbo GX network. 500 A shunts on each alternator output give the system precise per-engine current data. Engine room ventilation was evaluated, and forced-air cooling was added directing fresh air over each alternator to extend longevity under sustained high-output charging into a 1,840 Ah lithium bank.

To keep both engine start batteries topped up regardless of which charge source is active, dedicated DC-DC chargers were installed for each engine — replacing the old combiner-based approach with isolated, profile-matched charging.

Generator: 50 Hz to 60 Hz, properly tuned

The Northern Lights generator was reconfigured from 50 Hz to 60 Hz to match the boat's North American AC system. Engine speed was set to approximately 1,800 RPM for ~62 Hz unloaded — the right target for clean 60 Hz output once typical loads pull the frequency down a couple of hertz under operation. Output cabling was evaluated for ampacity and routed cleanly to the Quattros' generator input.

Cerbo GX: every system on one display

Every component reports into the Victron Cerbo GX. House batteries via Ethernet, both Arco Zeus regulators via Cerbo's data network, both Quattros via VE.Bus, the MPPT solar controller, and the generator. The Cerbo's Touch display lives at the main panel, giving the crew a single live view: shore power state, generator state, inverter/charger status, AC and DC loads, alternator current, solar yield, and battery state-of-charge — voltage, current, and watts, all in one glance.

AC panel and solar

The original AC distribution panel was removed along with its obsolete wiring, and a new Blue Sea Systems AC panel was installed with proper double-pole breakers for major loads (air conditioning, water heaters) and reused single-pole breakers for 120V branch circuits. The whole panel is now fully inverter-capable: every AC load on the boat can run from battery with appropriate power management. The existing solar array was integrated via a properly sized Victron MPPT charge controller, feeding the lithium bank under Cerbo GX control.

Documentation and handover

On handover, the owner received complete as-built diagrams covering the DC primary distribution, AC distribution, and the full Victron communications network — clearly labelled, suitable for service, troubleshooting, and future expansion.

The outcome

Tortuga left the dock with 1,840 Ah of usable lithium capacity, 10 kW of paralleled inverter power, externally regulated alternators delivering intelligently throttled charge through the Arco Zeus controllers, a 50 A shore inlet with full GFI and galvanic protection, and a unified Cerbo GX backbone tying every charge source and load into one coherent system. It's the kind of refit that turns a coastal-cruising catamaran into a boat that can stay out — long passages, long anchorages, with the crew always knowing exactly what the electrical system is doing.

Considering a lithium refit for your own Leopard catamaran or other cruising yacht? Get in touch — we'd be happy to talk through what a full electrical overhaul looks like for your boat.