DC-DC converters for sailboats — applications and selection 2026

The DC-DC converter is the least glamorous piece of equipment on a sailboat — and one of the most critical for electrical reliability. On a modern refit with a lithium service bank + lead starter + 24 V propulsion, you’ll need 2 to 5 units. Poorly chosen, they cause invisible intermittent faults. Properly sized, they keep the entire system running for 10-15 years without intervention.

This article details the 4 key applications, the Victron and Mastervolt ranges stocked by Skysat, and provides installation guidelines. For the lithium bank they protect, see switching to lithium.

4 key applications for sailboat DC-DC converters

1. Alternator protection for a lithium bank

Lithium requires 100 A from an 80 A alternator → overheating and failure. The DC-DC converter limits the current drawn to a safe value (typically 30-40 A). See our lithium plug & play article.

2. 12 ↔ 24 V conversion for mixed equipment

Yacht running 24 V but with 12 V equipment (standard fridge, N2K displays, USB) or vice versa. The DC-DC converter handles the voltage conversion with 90-94% efficiency.

3. Smart charging of a starter battery from a service bank

Lead starter battery kept charged by the lithium service bank via DC-DC. Eliminates the need for a dedicated shore charger for the starter battery.

4. Remote power supply for displays/PCs

Bus voltage varies 11-15 V depending on load. Sensitive displays prefer stable 12.5 V. An isolated-output DC-DC converter provides this stability.

Isolated vs non-isolated — selection rules

• Isolated: separate ground between input/output. Benefits: no ground-loop currents, reduced electrical noise, protection against ground loops. ~30-50% surcharge vs non-isolated.
• Non-isolated: common ground. Simpler and cheaper. Suitable when both sides share the same ground reference (standard pleasure-craft setup with a single negative battery ground).

Practical rule: isolated for voltage conversions between circuits (12→24 V, 24→12 V), non-isolated for alternator protection or charging between batteries at the same voltage.

Victron Orion range

Flagship DC-DC range for pleasure craft, from entry-level models at 100-150 € HT up to the XS 1400 at ~ 350 € HT.

• Orion-Tr Smart 12/12-30A non-isolated (~ 230 € HT): battery-to-battery charging without isolation. For maintaining a starter battery from a service bank.
• Orion-Tr Smart 12/12-18A isolated (~ 171 € HT): isolated version at the same voltage. For clean DC bus powering remote displays or PCs.
• Orion-Tr Smart 24/12-20A isolated (~ 171 € HT): 24→12 V conversion for N2K equipment and fridges on 24 V yachts.
• Orion-Tr Smart 24/24-17A: stabilized DC bus on 24 V yachts.
• Orion XS 1400 (~ 350 € HT): 50 A continuous, designed for protecting alternators charging large lithium banks. Our 2026 workshop standard for lithium refits.

Mastervolt DC Master range

Direct competitor to Victron, with MasterBus integration for CZone-equipped yachts.

• DC Master 12/12-6 isolated (~ 220 € HT): basic conversion for ECUs and sensitive electronics.
• DC Master 48/12-20 (~ 365 € HT): 48→12 V conversion for yachts with electric propulsion and 48 V banks.

Mastervolt is justified on new Bénéteau/Jeanneau yachts equipped with CZone (native dashboard integration); Victron for everything else.

Current and voltage sizing

1. Identify max downstream load. 4 A display + 6 A autopilot + 3 A continuous fridge = 13 A continuous.
2. Add 30% safety margin for peaks. 13 × 1.3 = 17 A.
3. Select DC-DC with nominal current ≥ 17 A. Orion-Tr Smart 12/12-18A (18 A nominal) or higher.
4. Check efficiency. 90-94% on modern Orions. For 18 A at 12 V = 216 W output, 240 W input → ~24 W dissipated as heat (requires ventilation).

2026 model comparison chart

Workshop installation — wiring and protection

3 real-world workshop cases — DC-DC installation

Case 1 — Bénéteau Oceanis 38 lithium conversion

200 Ah lithium bank + original 80 A alternator. Alternator protection via Orion XS 1400 (~ 350 € HT) limiting current to 50 A continuous. Preserves alternator under full lithium load. Total install: 450 € HT (DC-DC + wiring + 200 A class T fuse).

Case 2 — Bavaria 50 24 V yacht with 12 V fridge

2018 24 V yacht but Vitrifrigo C115 12 V fridge (Danfoss BD35 compressor). Solution: Orion-Tr Smart 24/12-20A isolated (~ 171 € HT) dedicated to fridge. Stable conversion, fridge cycles correctly, 24 V draw measured 4-5 A.

Case 3 — 38-foot sailboat — stabilized DC bus for displays

Multiple displays + sensitive onboard computer affected by voltage variations (raw 11-14.5 V while sailing). Installed Orion-Tr Smart 12/12-18A isolated (~ 171 € HT) with stable 12.8 V output. No more display reboots in 18 months.

Excluded alternatives — DC-DC not recommended

• Low-cost Chinese DC-DC (40-80 € HT): avoid. Often advertised 95% efficiency but real-world 80-85%, poor thermal management, possible short-circuit under overload. For 100 € HT difference, choose Victron or Mastervolt.
• Automotive-grade Camp Sport DC-DC (high-end): excellent for RVs but insufficient marine protection (IP20 enclosure). In marine humidity, lifespan 2-3 years vs 10+ years for Orion marine models.
• DIY DC-DC with discrete components: fun electronics project but no marine certification or support. Avoid for real sailboat installations.

Programming Orion via VictronConnect — key parameters

Once the Orion is installed, program via the VictronConnect app (Bluetooth Smart included on all Smart models):

• Minimum input voltage: set to 11.8 V (12 V lithium bank) to avoid deep discharge.
• Output voltage: 12.8 V stable for stabilized bus, 14.4 V for charging lead starter batteries.
• Maximum current: set according to input cable (safety). For 35 mm² cable, limit to 100 A.
• Mode: "ON/OFF" simple or "ON via Engine Sense" (activates only when engine is running and alternator is charging).

Skysat distributes Victron Energy and Mastervolt. 2026 HT prices are indicative distributor rates.