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 lithium house bank + lead starter + 24 V propulsion, you’ll find 2 to 5 units. Poorly chosen, they cause intermittent, invisible faults. Properly sized, they keep the whole 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 rules. For the lithium banks they protect, see transitioning to lithium.

4 key applications for DC-DC converters on sailboats

1. Alternator protection for lithium banks

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

2. 12 ↔ 24 V conversion for mixed-voltage equipment

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

3. Smart charging of starter batteries from house banks

Lead starter battery kept charged by the lithium house 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 provides this stability.

Isolated vs non-isolated — rules for selection

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

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

Victron Orion range

Flagship DC-DC range for pleasure craft, from entry-level models at $100–$150 USD ex-works up to the XS 1400 at ~ $350 USD ex-works.

• Orion-Tr Smart 12/12-30A non-isolated (~ $230 USD ex-works): battery-to-battery charger without isolation. For maintaining starter batteries from house banks.
• Orion-Tr Smart 12/12-18A isolated (~ $171 USD ex-works): isolated version for same-voltage use. For clean DC bus powering displays or remote PCs.
• Orion-Tr Smart 24/12-20A isolated (~ $171 USD ex-works): 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 USD ex-works): 50 A continuous, designed for protecting alternators on 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 USD ex-works): basic conversion for ECUs and sensitive electronics.
• DC Master 48/12-20 (~ $365 USD ex-works): 48→12 V conversion for yachts with electric propulsion and 48 V house 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 Orion models. For 18 A at 12 V = 216 W output, 240 W input → ~24 W dissipated as heat (requires ventilation).

Comparative model table 2026

Workshop installation — wiring and protection

3 real-world workshop cases — DC-DC installation

Case 1 — Bénéteau Oceanis 38 lithium conversion

200 Ah lithium house bank + original 80 A alternator. Alternator protection via Orion XS 1400 (~ $350 USD ex-works) limiting current to 50 A continuous. Preserves alternator under full lithium load. Total install: $450 USD ex-works (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 USD ex-works) dedicated to fridge. Stable conversion, fridge cycles correctly, 24 V draw measured 4–5 A.

Case 3 — 38 ft sailboat — stabilized DC bus for displays

Multiple displays + sensitive on-board computer intolerant of voltage swings (raw 11–14.5 V while sailing). Installed Orion-Tr Smart 12/12-18A isolated (~ $171 USD ex-works) with stable 12.8 V output. No display reboots in 18 months.

Excluded alternatives — DC-DC not recommended

• Low-cost Chinese DC-DC (40–80 USD ex-works): avoid. Advertised efficiency often 95% but real-world 80–85%, poor thermal management, risk of short-circuit under overload. For $100 USD difference, choose Victron or Mastervolt.
• Automotive-grade DC-DC (e.g., Camp Sport): excellent for RVs but insufficient marinization (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 lacks marine certification and support. Avoid for real-world sailboat installations.

Programming Orion via VictronConnect — key parameters

After installing the Orion, program via 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 display bus, 14.4 V for lead starter battery charging.
• Max current: set to match input cable rating (safety). For 35 mm² cable, limit to 100 A.
• Mode: "ON/OFF" simple or "ON via Engine Sense" (activates only when engine runs and alternator is charging).

Skysat distributes Victron Energy and Mastervolt. 2026 ex-works prices are indicative of authorized distributor rates.