Full Lithium Rewire & Electrical Refit
From corroded chaos to a fully engineered Victron lithium system - every single cable replaced, every circuit properly sized and fused. Winter 2023/24 project, December to March.
The Problem
When we bought Lagertha, the electrical system had accumulated decades of "improvements" - tapped wires, corroded terminals, melted chocolate block connectors, and no proper fusing. The old AGM batteries were past their best, cable runs had been added piecemeal with no regard for circuit length or load, and insulation was cracking and peeling on several runs. Green corrosion on terminals, melted plastic on connectors - it was only a matter of time before something failed at sea.
The old switch panel told the story - faded labels, a breaker wrapped in blue tape with an X marked on it for "water maker", and wiring that looked like a bird's nest behind it.
Clean Sheet Design
We didn't patch - we started from scratch. No cable was left old. Every run was calculated for its actual circuit length and current, sized accordingly, and properly fused. This isn't a one-size-fits-all job; each cable gauge was chosen for the specific load and distance it serves. All wiring is tinned marine-grade, with proper crimps for fine-stranded battery cables.
The DC System: Victron Lithium
Batteries: 2x Victron Smart Lithium 330Ah (660Ah total) - enough capacity to run the boat for days without charging.
Battery Management: Victron Lynx Smart BMS 500, Lynx Power In, and Lynx Distributor 1000 - a single modular busbar system that gives us cell monitoring, disconnect control, and proper fuse distribution in one clean package.
Charging: 3x Victron MPPT 100/30 solar controllers, plus the Quattro handles shore power and generator charging. The alternator charges the engine starter battery directly, and an Orion XS DC-DC charger then feeds the lithium house bank from the starter - keeping things simple.
Battery Protect: Fitted on the non-essential loads bus - if voltage drops too low, it sheds the non-essential circuits without killing navigation or safety systems.
The AC System: Quattro + Shelly
Victron Quattro 3kVA inverter/charger - the heart of the AC system. It manages two AC inputs (shore power and our Whisper 3.5kW generator) with automatic transfer switching. No manual changeover needed.
Quattro Bypass: We built a dedicated bypass panel with properly rated breakers so that both shore power and generator can feed the boat AC directly, bypassing the Quattro entirely for servicing.
AC Monitoring: Shelly smart relays on all four AC circuits, each individually monitored and switchable:
- Sockets 1 - V-berth, locker, chart table
- Sockets 2 - Aft cabin, galley, saloon
- Chargers - two smart battery chargers: one for the engine starter, one for the generator starter
- Calorifier - water heater with a twist...
Calorifier automation: When on shore power, it switches on automatically at 6am so we have hot water when we wake up. When switched on manually, it auto-shuts off after 45 minutes.
The New AC Distribution Panel
Circuit breakers, clearly labeled circuits, reverse polarity warning, and a Shelly display showing real-time consumption per circuit. A far cry from the faded labels and taped-up breakers we started with.
DC Switch Panel & Cerbo GX
Clean rotary switches for engine battery (OFF/1/2/BOTH), house battery (OFF/ON), and Quattro inverter (OFF/ON), plus a dedicated windlass thermal breaker.
Cerbo GX ties it all together - monitoring every Victron device, running Signal K for instrument data, and Node-RED for our automations (calorifier timing, alerts, and more).
Zero Old Cable
The most important thing: every single cable was replaced. Nothing was left from the old system. No splicing into ancient runs, no "that looks okay for now". Clean sheet, clean design, clean installation.
On crimps: we used proper cup-style dies for fine-stranded marine cable, not hexagonal dies. Both make contact, but hex crimps compress the strands too aggressively and can create high-resistance hot spots over time. The right tool for the right cable - that's the standard we set for this refit.