Shore power charger or lithium bank combi: how to choose

By Pol Conin — Skysat, marine electronics workshop in Carnac. Published 10 July 2026, updated 23 October 2026.

Replacing a lead-acid battery bank with lithium without changing the charger is the most common mistake in an energy refit: a shore-power charger designed for lead-acid applies voltages and stages that the lithium battery manufacturer did not intend. This guide provides the criteria for choosing a shore-power charger or combi suited to a lithium bank. It complements our guide to electricity on a sailboat, which starts with an energy audit.

Criterion 1: an adjustable lithium mode

The charge voltage, absorption duration, and float voltage are set by the battery manufacturer, not the charger manufacturer. The charger must therefore offer a lithium mode and allow these values to be adjusted.

Example: for its Smart and NG lithium batteries, Victron specifies an absorption voltage of 14.2 V (28.4 V in 24 V) for at least two hours, followed by a float voltage of 13.5 V (27 V), and prohibits charging below 5 °C. Victron Blue Smart chargers apply these values in their "Li-ion" mode, which can then be adjusted via the VictronConnect app; in Li-ion mode, they do not charge below 0 °C.

At Mastervolt, MLI Ultra batteries are charged at 14.25 V in absorption and 13.5 V in float (28.5 V and 27 V in 24 V). The ChargeMaster Plus and Mass chargers, as well as the brand’s combis, offer a dedicated "Lithium-ion (MLI)" profile; the ChargeMaster Plus manual specifies that it applies to Mastervolt MLI batteries only, not to other lithium batteries. The EasyCharge charger, however, has no lithium profile: its manual reserves it for lead-acid batteries.

Criterion 2: the BMS must be able to stop the charger

The BMS of a lithium bank cuts off charging when a cell reaches its limit or when the temperature falls outside the allowed range. It does so in two ways: by opening a contactor, or by instructing chargers to stop. The latter is preferable, and it requires the charger to be able to receive the command.

• Via a hardwired « remote on/off » input connected to a BMS output (often labeled « allowed-to-charge »). For Victron, this is documented on the Smart IP43, Skylla-i and Skylla IP65 chargers, as well as on the Orion XS DC-DC charger. The datasheets and manuals for the Blue Smart IP22, IP65 and IP67 do not mention a remote input.
• Via a communication bus: VE.Can on Victron (isolated port on the Skylla-i), MasterBus on Mastervolt, CAN on MG Energy Systems, where the Master LV master BMS controls chargers via its charge-enable outputs or via CAN.

On Mastervolt systems, the MLI Ultra battery sends a "Stop charge" event over the MasterBus to shut down Mastervolt chargers when voltage or a cell exceeds its limit. The battery manual strongly recommends this for every charging source, including the alternator, and the ChargeMaster Plus manual makes it mandatory with an MLI Ultra.

If the charger cannot receive any command, the BMS can only cut power via its contactor: this is a last-resort protection, not normal operation.

Criterion 3: the correct current

The charging current is limited by two boundaries:

• Maximum: what the battery can accept. This is a manufacturer specification. Victron recommends 0.5 C for its Smart and NG batteries, i.e., a current equal to half the capacity: 100 A maximum for a 200 Ah bank (Skysat calculation based on Victron recommendation). Mastervolt recommends a maximum of 80 A for an MLI Ultra 12/3000 (230 Ah) and 160 A for a 12/6000 (460 Ah). For the 24/6000, the manual states 80 A and the datasheet 60 A: until Mastervolt clarifies, use 60 A.
• Minimum: what is needed to restore the deficit during the time spent in harbor. If you return from a weekend with 150 Ah to restore and the boat remains connected for 10 hours, 15 A is sufficient on paper; if you want to depart after two hours, much more is required.

With multiple chargers or a charger and a combi, currents add up: the total must remain below the battery’s limit.

Beware of chargers with multiple outputs: with Victron, a Blue Smart IP22 with three outputs can deliver the rated current on each output, but the total is capped at the rated current. On the "(1+1)" versions of Smart IP43 and Skylla-i, the second output, around 4 A, is intended for maintaining the starter battery.

What the charger demands from the shore power inlet

A charger draws from the 230 V side the power it delivers to the battery bank, plus its losses. A 30 A charger charging a 12 V bank at 14.2 V delivers about 430 W; with an efficiency of around 90 %, it draws about 475 W from the shore power inlet, i.e., just over 2 A at 230 V (Skysat calculation, approximate value). The shore power inlet is therefore almost never the limiting factor for a single charger. It becomes one when the water heater, heating or air conditioning are running simultaneously: this is where a combi with input current limiting becomes useful.

Victron and Mastervolt chargers compared

Manufacturer datasheet values. “Remote control via BMS” means a documented remote input or bus in the datasheet or manual; “not documented” does not mean impossible, but that we have not found it in the manufacturer’s documents.

Sources: Victron Energy and Mastervolt datasheets and manuals listed at the end of the article. Models without a link have no datasheet available on Skysat at this time: request them from us.

Standalone charger or inverter-charger combi?

A combi combines in a single enclosure a charger, an inverter (which generates 230 V from the battery) and a transfer relay. In harbor, it charges and passes through 230 V to the boat; at sea, it switches to the inverter.

• Victron MultiPlus-II 12/3000/120-32: 3 000 VA inverter (2 400 W at 25 °C, 5 500 W peak), 120 A charger, up to 32 A transfer. MultiPlus-II 24/5000/120-50: 5 000 VA inverter (4 000 W at 25 °C, 9 000 W peak), 120 A charger, up to 50 A transfer. Switching in under 20 ms.
• Limit shore power draw. The MultiPlus-II can be set to a maximum input current: it reduces charging to avoid tripping the dockside breaker (PowerControl), and can draw from the battery to supplement insufficient shore power (PowerAssist).
• The cost: 13 W standby consumption for the 12/3000 (9 W in AES mode, 3 W in search mode) and 18 W for the 24/5000, per Victron. Over 24 hours at anchor, 13 W equates to roughly 26 Ah on a 12 V bank (Skysat calculation): factor this into your energy budget, or disconnect when 230 V shore power is not in use.
• Lithium mode: the MultiPlus-II manual tables default to lead-acid voltages; the algorithm is adjusted for lithium via the VEConfigure software. With Victron Smart batteries, the combi is controlled by a VE.Bus BMS V2 or a Lynx Smart BMS.

• Mastervolt CombiMaster 12/3000-100: 3 000 VA inverter (2 600 W at 40 °C), 100 A charger, up to 25 A transfer, power sharing with shore power and assistance, MasterBus and CZone compatibility. Standby consumption: 30 W (10 W in economy mode).
• Mastervolt Mass Combi Ultra 12/3000-150 : 3,000 W continuous (6,000 W peak), 150 A charger, seamless transfer (under 1 ms), integrated solar MPPT regulator from hardware version R, MasterBus. Idle consumption: 26 W (7 W in economy mode). The 24/3500-100 version delivers 3,500 W and charges at 100 A.
• Both Mastervolt combis use PWM profiles for the brand’s batteries.

If you only need 230 V at the harbor, a standalone charger is enough. If you want 230 V at sea for a few devices, compare a combi with a charger + small inverter: our electricity on board guide details inverter sizing.

Limitations and pitfalls

• Keep the lead-acid charger. Even if labeled « lithium-compatible » on the tag, it must apply the voltages specified by your battery manufacturer. Check this in the battery’s datasheet before reusing it.
• Add currents without realizing it. Shore charger, combi, solar, and alternator may charge simultaneously: the total must remain below the current recommended by the battery manufacturer.
• Charging in cold weather. Victron prohibits charging its lithium batteries below 5 °C. A boat left outside in winter and still connected must be able to cut its charging.
• Relying on the BMS contactor. If it cuts while a charger or alternator is delivering power, it protects the battery, not the rest of the installation.
• Trusting a value from this page over your battery’s datasheet. The examples above apply to the products cited; your battery’s datasheet takes precedence.

Skysat has not tested these chargers for this article: it relies solely on the manufacturers’ documentation.

Our verdict by situation

• Small bank, boat often in harbor, no BMS controlling the chargers : a Blue Smart set to lithium mode, IP65 or IP67 if installed in an exposed locker. First check that your battery architecture does not require a controlled shutdown via the BMS.
• 24 V bank with a BMS controlling the charge : a charger with remote input or bus, such as the Smart IP43 or the Skylla-i.
• Wet or exposed locker, need for high power at 12 V : the Skylla IP65 (70 A at 12 V), with remote input.
• Need for 230 V on board or weak shore power : a combi like the MultiPlus-II, including its idle consumption in the energy balance.

Sources

Manufacturer documents consulted on 22 October 2026:

• Victron Energy: datasheets and manuals for Blue Smart IP22 chargers (manual rev. 05, 08/2025), Blue Smart IP65, Blue Smart IP67 (manual rev. 02, 09/2021), Smart IP43, Skylla-i, Skylla IP65 and Skylla-TG (manual rev. 05, 06/2025); datasheet and manual for MultiPlus-II 230 V (rev. 14, 07/2026); manuals for Lithium Smart Battery (rev. 21, 01/2026) and Lithium NG 12.8 V (rev. 11, 03/2026).
• Mastervolt: MLI Ultra manual (rev. 10) and MLI Ultra datasheets; ChargeMaster Plus manual (10000016594/06, 09/2025); Mass 24/50 to 48/50 manual (10000001888/05, 12/2023); EasyCharge manual (10000009118/03); CombiMaster 230 V manual (10000015079/11, 09/2025); Mass Combi Ultra manual (10000006554/10).
• MG Energy Systems: Master LV communication guide and manual; online documentation from MG on CAN-compatible chargers.

See also

• Electricity on board a sailboat: lithium, charging, conversion, solar
• Victron, Mastervolt or MG Energy: which lithium ecosystem?
• Collections: AC/DC chargers and combis, inverters, Victron Energy, Mastervolt

Disclosure: Skysat distributes Victron Energy, Mastervolt, and MG Energy Systems. Article neither sponsored nor reviewed by these brands.