The essentials in 30 seconds
- Rule of thumb: dockside charger at 30% of the raw lithium bank capacity. 200 Ah bank = 60 A charger minimum. 400 Ah bank = 120 A charger.
- Mandatory LFP profile. Never use lead-acid profile (destructive overvoltage). All Victron Blue Smart, Skylla-i, and MultiPlus chargers have LFP profile as standard in 2026.
- Brands stocked: Victron Blue Smart IP65 12V 25A (~ 350 € HT), 24V 13A (~ 215 € HT), Skylla-i 24V 100A (~ 1 200 €), Mastervolt ChargeMaster.
- MultiPlus combo inverter: 120–200 A charger + 3 000 W inverter in a single unit. Skysat standard for compact sailboat refits 40+ feet.
- 230 V harbor power: 60 A 12 V charger = 800 W on AC side = 3.5 A at 230 V. Always below the standard 16 A harbor outlet rating.
The dockside charger is the forgotten component in a lithium refit. After replacing the bank, many sailors keep the old lead-acid dockside charger — which slowly destroys the new cells with an unsuitable charging profile. This article explains correct sizing and the brands stocked at Skysat.
For the lithium bank it powers, see sizing your sailboat lithium bank.
Sizing the charger for a lithium bank
Rule of thumb: 30% of raw bank capacity. Example:
- 100 Ah bank → 30 A charger minimum.
- 200 Ah bank → 60 A charger.
- 400 Ah bank → 120 A charger (prefer MultiPlus combo).
- 600+ Ah bank → 150–200 A charger (MultiPlus II).
Why 30%? A compromise between recharge speed (bank charged to 80% DoD in 3–4 h) and cell longevity (acceptable thermal stress, no strain). Going beyond (50%) speeds up recharge but reduces lifespan.
LFP profile — why it’s mandatory
The charger applies a specific charging profile depending on battery chemistry. For LiFePO4:
- Bulk: 14.4 V (12 V bank) or 28.8 V (24 V bank), maximum current.
- Absorption: 14.4 V for 30–60 min until full charge.
- Float: 13.5–13.8 V (never continuous 14.4 V = cell stress).
A lead-acid profile (14.7 V absorption + permanent 13.8 V float) on lithium destroys cells in 6–12 months. All modern Victron chargers have selectable LFP profile via VictronConnect.
Victron Blue Smart — entry and mid-range
- Blue Smart IP65 12V 25A: ~ 350 € HT. For 80–120 Ah 12 V lithium banks.
- Blue Smart IP65 24V 13A: ~ 215 € HT. For 24 V 50–100 Ah banks.
- Blue Smart IP67 12V 50A: ~ 480 € HT. For 150–200 Ah banks.
Smart = Bluetooth via VictronConnect for monitoring + LFP profile configuration. IP65/67 = acceptable waterproofing in damp lockers.
Victron MultiPlus — inverter combo
The MultiPlus combines a 50–200 A dockside charger + 800–5 000 W DC/AC inverter in one enclosure. Automatic transfer between harbor power and battery in under 20 ms.
- MultiPlus 12/3000-120: 120 A charger + 3 000 W inverter. ~ 1 850 € HT.
- MultiPlus II 12/3000-120: new version, built-in monitoring. ~ 1 950 € HT.
- MultiPlus II 24/5000-120: 120 A 24 V + 5 000 W inverter. ~ 2 800 € HT. For 45+ ft yachts.
Benefit: saves space in the technical locker (1 unit instead of 2), intelligent harbor power management (limits input current if breaker trips).
Skylla-i and Mastervolt ChargeMaster — high-end
- Victron Skylla-i 24V/100A: ~ 1 200 € HT. Professional marine charger, IP21.
- Mastervolt ChargeMaster Plus 12/35-3: ~ 580 € HT. 3 independent outputs (house/start/3rd bank).
- Mastervolt ChargeMaster Plus 12/50-3: ~ 750 € HT.
- Mastervolt ChargeMaster Plus 24/20-3: ~ 680 € HT for 24 V yachts.
2026 model comparison chart
| Model | Voltage | Current | Outputs | Price HT |
|---|---|---|---|---|
| Blue Smart IP65 12V 25A | 12 V | 25 A | 1 | ~ 350 € |
| Blue Smart IP65 24V 13A | 24 V | 13 A | 1 | ~ 215 € |
| Blue Smart IP67 12V 50A | 12 V | 50 A | 1 | ~ 480 € |
| MultiPlus 12/3000-120 | 12 V | 120 A + 3 kW inverter | 2 | ~ 1 850 € |
| Mastervolt ChargeMaster Plus 12/35-3 | 12 V | 35 A | 3 outputs | ~ 580 € |
| Mastervolt ChargeMaster Plus 12/50-3 | 12 V | 50 A | 3 outputs | ~ 750 € |
| Skylla-i 24V/100A | 24 V | 100 A | 1 | ~ 1 200 € |
Installation and 230 V wiring
Workshop rules — dockside charger wiring
- 230 V 3-wire cable (live + neutral + earth): 1.5 mm² up to 16 A, 2.5 mm² above.
- 30 mA RCD between harbor outlet and charger (ISO 13297 standard).
- Bonding earth connection: mandatory between charger case and boat ground.
- DC cable sized for max current + 30%: Blue Smart 50 A → minimum 10 mm² cable.
- Class T fuse on charger output: rated 1.5× nominal current.
- Set LFP profile via VictronConnect before commissioning.
FAQ — Practical dockside charging
Can my old lead-acid charger charge lithium?
No, never. Lead-acid profile (14.7 V absorption + permanent 13.8 V float) destroys lithium cells in 6–12 months. Mandatory replacement for lithium conversion.
Is a charger too powerful for my bank?
Not dangerous, but pointless. A 100 A charger on a 100 Ah bank charges in 1 h instead of 3 h, but adds thermal stress and wasted current (BMS limits). No technical or economic benefit. Stick to the 30% rule.
How long to recharge a 200 Ah bank?
With a 60 A charger: ~ 3 h Bulk + 1 h Absorption = 4 h to go from 20% to 100% SOC. One night at the harbor is plenty.
Are multi-bank outputs essential?
Useful if you have multiple banks (house/start/3rd). The Mastervolt ChargeMaster Plus 3 outputs charge each bank intelligently. Otherwise, a single-output charger + Argofet (battery separator) at 80–120 € HT works.
What harbor power is available?
Standard European harbor outlets: 16 A single-phase = 3 680 W max. Premium ports on the French Riviera: 32 A = 7 360 W. Always below the port and boat breakers.
Skysat stocks Victron Energy and Mastervolt. 2026 distributor list prices are indicative.
