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, 2 to 5 units are typically installed. Poorly chosen, they cause intermittent, invisible faults. Properly sized, they run the entire system without intervention for 10-15 years.

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

4 key applications for sailboat DC-DC converters

1. Protection of lithium house bank from alternator

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

2. 12 ↔ 24 V conversion for mixed equipment

Yacht in 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 battery from house bank

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

4. Remote power supply for displays/PCs

House bank voltage varies 11-15 V depending on load. Sensitive displays prefer stable 12.5 V. Isolated-output DC-DC provides this stability.

Isolated vs non-isolated — selection rules

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

Practical rule: use isolated for voltage conversions between circuits (12→24 V, 24→12 V); use 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 € HT 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 starter battery from house bank.
• Orion-Tr Smart 12/12-18A isolated (~ 171 € HT): isolated version for same voltage. For clean DC bus powering displays or remote 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 house 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 house bank.

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. Choose 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 table

Workshop installation — wiring and protection

3 real-world workshop cases — DC-DC installations

Case 1 — Bénéteau Oceanis 38 lithium conversion

200 Ah lithium house bank + original 80 A alternator. Alternator protection via Orion XS 1400 (~ 350 € HT) limiting alternator current to 50 A continuous. Preserves alternator under full lithium load. Total install: 450 € HT (DC-DC + wiring + class T 200 A 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, correct fridge cycling, 24 V consumption measured at 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. Advertised efficiency often 95% but real-world 80-85%, poor thermal management, risk of short-circuit under overload. For ~100 € extra, choose Victron or Mastervolt.
• Automotive-grade DC-DC (e.g., Camp Sport): excellent for RVs but insufficient marine rating (IP20 enclosure). In marine humidity, lifespan 2-3 years vs 10+ years for marine-rated Orion.
• 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 installation, 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.
• Maximum current: set according to 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 HT prices are indicative distributor pricing.