The essentials in 30 seconds
- 4 key applications: (1) alternator protection for a power-hungry lithium bank, (2) 12↔24 V conversion for mixed equipment, (3) smart charging of a starter battery from a house bank, (4) remote power supply for displays/PCs with stable voltage.
- Isolated vs non-isolated: isolated = separate ground for input/output, essential when mixing 12 V banks or needing a clean ground reference. Non-isolated = simpler and cheaper, OK when both sides share the same ground.
- 2026 standards: Victron Orion XS 1400 (~ 350 € HT) for alternator protection in lithium setups. Orion-Tr Smart 12/12-18A isolated (~ 171 € HT) for standard uses.
- Sizing = max current + 30%. 30 A continuous output → converter rated at least 40 A to avoid saturation and dropouts.
- Typical refit budget: 200-600 € HT for DC-DC + wiring + protection. Huge difference in the longevity of the bank and the reliability of the electrical system.
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 house bank + lead-acid starter + 24 V propulsion, you’ll typically need 2 to 5 units. Poorly chosen, they cause intermittent, invisible 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 transitioning to lithium.
4 key applications for DC-DC converters on sailboats
1. Alternator protection for a lithium bank
Lithium banks demand 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 adjusts the voltage with 90-94% efficiency.
3. Smart charging of a starter battery from a house bank
Lead-acid starter battery kept charged by the lithium house bank via DC-DC converter. Eliminates the need for a dedicated shore charger for the starter battery.
4. Remote power supply for displays/PCs
Bus voltage varies between 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 for input/output. Benefits: no ground-loop currents, 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 a single negative battery ground).
Practical rule: use isolated converters 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 € 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 house bank.
- Orion-Tr Smart 12/12-18A isolated (~ 171 € HT): isolated version for 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 in 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
- Identify the maximum downstream load. 4 A display + 6 A autopilot + 3 A continuous fridge = 13 A continuous.
- Add 30% safety margin for peaks. 13 × 1.3 = 17 A.
- Select a DC-DC converter with a nominal current ≥ 17 A. Orion-Tr Smart 12/12-18A (18 A nominal) or higher.
- 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 (needs ventilation).
Comparative table of 2026 models
| Model | Type | Voltage | Max current | Isolated | Price HT |
|---|---|---|---|---|---|
| Orion-Tr Smart 12/12-18A | Stabilized bus | 12→12 V | 18 A | Yes | ~ 171 € |
| Orion-Tr Smart 12/12-30A | Battery charging | 12→12 V | 30 A | No | ~ 230 € |
| Orion-Tr Smart 24/12-20A | Conversion | 24→12 V | 20 A | Yes | ~ 171 € |
| Orion-Tr Smart 24/24-17A | Stabilized bus | 24→24 V | 17 A | Yes | ~ 220 € |
| Orion XS 1400 | Alternator protection | 12→12 V | 50 A | No | ~ 350 € |
| DC Master 12/12-6 isolated | Sensitive conversion | 12→12 V | 6 A | Yes | ~ 220 € |
| DC Master 48/12-20 | High-power conversion | 48→12 V | 20 A | Yes | ~ 365 € |
Workshop installation — wiring and protection
Skysat workshop rules
- Cables for input and output rated for max current + 30%. Orion 30 A → minimum 6 mm² cable.
- Class T or MEGA fuse in series on the input. Rated at 1.2× nominal current.
- Mandatory ventilation. Heat dissipation 10-30 W depending on model. Do not install in a closed cabinet.
- Position close to the power source battery. Short input cable = less power loss.
- Programming via VictronConnect. Set output voltage, max current, and charge profile specific to the application. Must be configured at commissioning.
FAQ — DC-DC in practice
How many DC-DC converters on a typical 40-foot sailboat?
2-4 units: (1) Orion XS alternator protection, (2) Orion-Tr 12/12 for stabilized display bus, (3) Orion-Tr 12/12 to maintain a lead-acid starter battery if using a lithium house bank, (4) optional 24/12 if the yacht has partial 24 V systems.
Do DC-DC converters make noise?
Very little in practice. Fans on models ≥ 30 A can be audible (40-50 dB) nearby. Models ≤ 20 A are silent (passive heatsink).
Is Bluetooth Smart useful?
Yes for monitoring: voltage, current, temperature, history. Allows remote detection of faults via VictronConnect. ~50-80 € HT surcharge, cost-effective from the first avoided service call.
Difference between Orion Tr Smart and Orion XS?
Tr Smart = entry/mid-range, designed for stabilized bus and conversion. XS = heavy-duty, designed for alternator protection in lithium banks (50 A continuous). Choose based on application.
Can DC-DC converters be wired in parallel for more power?
Technically possible but not recommended without a load-sharing system. Better to choose a larger model directly.
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 using Orion XS 1400 (~ 350 € HT) limiting current to 50 A continuous. Preserves the 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 the fridge. Stable conversion, fridge cycles correctly, 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 display reboots in 18 months.
Excluded alternatives — DC-DC converters not recommended
- Low-cost Chinese DC-DC converters (40-80 € HT): avoid. Often advertised as 95% efficient but real-world efficiency is 80-85%, thermal dissipation poorly controlled, risk of short-circuit under overload. For ~100 € HT more, choose Victron or Mastervolt.
- Automotive-grade DC-DC converters (e.g., Camp Sport): excellent for RVs but insufficient marinization (IP20 enclosure). In marine humidity, lifespan is 2-3 years vs 10+ years for marine-grade Orion units.
- DIY DC-DC converters using discrete components: fun electronics project but lacks marine certification and support. Avoid for real-world 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 a stabilized bus, 14.4 V for charging a lead-acid starter battery.
- 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 the engine is running and the alternator is charging).
Skysat distributes Victron Energy and Mastervolt. 2026 HT prices are indicative distributor pricing.
