Victron Marine Electrical System: Shore Power Guide

A Victron marine electrical system has to solve two problems that land-based systems don’t: galvanic corrosion from shore power, and charging several battery banks from shore, engine and solar. Victron makes gear for each job. This guide walks through the shore-power side first, then charging, using Victron’s own datasheets.

Electrical work can be dangerous: follow the manual, fuse and size every cable correctly, and use a licensed electrician for anything connected to household wiring.

A Victron isolation transformer video.

Why Shore Power Causes Corrosion

Victron’s isolation transformer datasheet explains it this way. When the shore-side ground wire connects to the boat’s metal parts, the boat’s underwater metals (shaft, propeller, anodes) become part of a galvanic circuit with other boats and the marina. Anodes dissolve quickly, then the shaft and propeller get attacked.

Leaving the shore ground disconnected is “extremely dangerous,” Victron says, because GFCIs won’t work and fuses won’t blow on a short to metal parts.

The Victron Marine Electrical System Fix: Isolation Transformers

An isolation transformer removes any electrical continuity between shore power and the boat. Shore power feeds the primary side, and the boat runs from the secondary. With the boat’s metal parts bonded to the secondary neutral, a GFCI trips or a fuse blows on a fault. Victron says this also removes the need for galvanic isolators and polarity alarms.

Model	Input / output	Rating	Weight
2,500W	115 or 230V	22 / 11A	12.1kg
4,500W	115 or 230V	38 / 19A	22.2kg
4,500W Auto 115/230V	auto-switching	38 / 19A	21.8kg
8,000W	230V	35A	28.17kg

Source: Victron Isolation Transformers 2500W, 4500W, 8000W datasheet. Victron’s product page also lists 2,000W, 3,600W and 7,000W models.

All have soft start, so the transformer’s inrush current doesn’t trip the shore breaker, plus a toroidal core and an input breaker. The 2,500W and 4,500W units can also step 115V up to 230V, or 230V down to 115V,. Enclosures are IP21.

Charging On Board

Shore charging: a Victron inverter/charger (MultiPlus or Quattro), or a dedicated charger. The Skylla-i and Skylla-IP65 offer multiple isolated outputs. The Blue Smart IP67 is fully sealed.
Engine charging: Orion XS or Orion-Tr Smart DC-DC chargers for lithium house banks. Cyrix combiners and Argo FET isolators split alternator charge between banks.
Solar: a SmartSolar MPPT sized to your arch or bimini panels.
Monitoring: a SmartShunt or BMV-712, plus a GX device.

Wiring Order

Shore inlet → isolation transformer → AC panel and inverter/charger.
Battery banks with a main fuse on each positive, then busbars and DC distribution.
Charge sources into the house bank, and the starter battery fed through a DC-DC charger or isolator.

Follow ABYC (or your local code), and have a marine electrician sign off.

Want the source figures? The Isolation Transformers page on Victron’s site has the datasheet.

Worked Example: Wiring an Isolation Transformer on a 115V Boat

A 38-foot boat on 30A 115V shore power with a 4,500W isolation transformer:

Shore inlet cable feeds the transformer’s primary through its input breaker.
The secondary feeds the boat’s AC panel, and the boat’s metal parts are bonded to the secondary neutral, as Victron’s datasheet describes.
Soft start stops the pedestal breaker tripping when the transformer is first switched on.
At 38A on 115V, the 4,500W model has headroom above a 30A pedestal.
With the boat out of the water, Victron recommends connecting the secondary neutral to ground.

Worked Example: Charging Three Banks on a Cruising Boat

A cruising catamaran with a 24V lithium house bank, two 12V starter batteries and solar on the hardtop:

Shore: a MultiPlus-II 24V charges the house bank and supplies 230V or 120V loads through the isolation transformer.
Engines: an Orion-Tr Smart isolated DC-DC charger on each engine charges the 24V house bank from the 12V engine systems, keeping negatives separate.
Solar: a SmartSolar MPPT feeds the house bank from hardtop panels.
Starter batteries: kept topped up by their own alternators.
Monitoring: a SmartShunt and a Cerbo GX show everything on the chartplotter.

Worked Example: Converting 230V Shore Power to 115V

A US-built boat cruising in Europe can use the 2,500W or 4,500W transformer to step a 230V supply down to 115V for its onboard systems. The 4,500W model handles 19A at 230V on the primary side, and the boat continues to see 115V on the secondary (example use).

Choosing the Transformer Size

Shore supply	Good fit
—	—
115V up to about 22A	2,500W
115V 30A pedestal	4,500W
Mixed 115V and 230V marinas	4,500W Auto 115/230V
230V up to 35A	8,000W

Mounting Notes

The 12.1–28.17kg weight needs a strong, low mounting point.
IP21 enclosures need a dry, ventilated compartment away from bilge water.
Keep shore cables short between the inlet and the transformer.
Have a marine electrician check bonding and grounding to ABYC or local code.

Charger Options for Multiple Banks

Skylla-i and Skylla-IP65: multiple isolated outputs from one charger, suited to larger boats.
Blue Smart IP67: fully sealed, one per bank, for wet locations.
MultiPlus or Quattro: a charger plus inverter, with the Quattro accepting two AC inputs.

Monitoring the Whole System

A Cerbo GX ties the inverter/charger, MPPTs, DC-DC chargers and battery monitor together, and sends battery and tank data over NMEA 2000 to the chartplotter. VRM adds remote access when the boat has internet.

Planning for Future Upgrades

Size the shore inlet, cable and transformer for the largest supply you expect to use, not just today’s pedestal. Leave space for a second MPPT or a larger inverter/charger, and run a spare cable for a future GX Touch at the helm. Upgrades later are much easier when the cable routes are already there.

FAQ

Do I need a galvanic isolator if I have an isolation transformer?

Victron says the isolation transformer eliminates the need for one.

What should I do with the transformer when the boat is out of the water?

Victron recommends connecting the secondary neutral to ground.

Does an isolation transformer waste power?

There’s a small no-load loss whenever it’s energised. On shore power that’s rarely noticeable.

Can I run my generator through the isolation transformer?

The transformer is for shore power. An onboard generator is usually wired to the boat’s AC system through a transfer switch or the Quattro’s second input.

Which charger suits a fully wet engine room?

The Blue Smart IP67, which is fully sealed in resin.

Sources: Victron Isolation Transformers 2500W/4500W/8000W datasheet; Isolation Transformers product page; Skylla-i, Skylla-IP65 and Blue Smart IP67 datasheets, victronenergy.com, accessed Oct 2026.