Victron Energy MultiPlus-II Inverter/Charger, 12V, 3000VA, 120A Charger, 120V AC, 50A Transfer Switch

Overview

The Victron Energy PMP122305120 is a MultiPlus-II 12/3000/120-50 120V inverter/charger for 12V battery systems that combines a 120V AC inverter, battery charger, and automatic transfer switch in one unit. It supports a 9.5 to 17V DC input range, delivers 3000VA inverter capacity, and charges at up to 120A, making it a practical power hub for boats with larger house banks, shore power, generator input, and AC loads on board.

This model is suited to marine electrical systems where the boat needs stable AC power underway, at anchor, or during dockside use. The 50A transfer switch manages AC input, while PowerControl and PowerAssist help limit shore or generator overload by reducing charge current or adding battery power during short peaks in demand.

The unit has two AC outputs. The main output can take over in less than 20 milliseconds when shore or generator power drops out, which helps keep sensitive electronics running through a power changeover. The second AC output is active only when AC input is available, useful for loads that should not drain the battery bank when the vessel is away from shore power.

Key features

• 12V inverter/charger with 3000VA output capacity and 120V AC output at 60 Hz for onboard AC systems.
• Up to 120A battery charging for 12V house banks when connected to shore power or a generator.
• 50A transfer switch with a 90 to 140V AC input range for typical 120V dockside and generator installations.
• PowerAssist can add battery power when shore or generator input is limited, helping prevent nuisance overloads during short demand peaks.
• UPS-style transfer in less than 20 milliseconds helps maintain power to computers, navigation support electronics, and other sensitive AC loads.
• Two AC outputs allow critical loads to remain on inverter power while selected non-critical loads operate only when AC input is present.
• VE.Bus communication supports system integration, remote monitoring, parallel operation, split-phase setups, and three-phase configurations when properly configured.
• Compatible with GX monitoring equipment and VRM remote access when added to a larger Victron system.
• Steel enclosure with IP22 protection rating for installation in a dry, protected electrical space on board.
• UL458 listing supports use in mobile and marine-style AC power systems where that listing is required.

Installation and setup

This inverter/charger should be mounted in a protected electrical compartment with ventilation and access for service. Its IP22 rating means it belongs away from bilge water, washdown spray, cockpit splash zones, and direct weather exposure. Fan-assisted cooling and the 42 lb weight also make solid mounting and clear airflow important.

Battery connections use M8 bolts, and the 120V AC connection is sized for 13 mm² or 6 AWG conductors. The installation should be planned around cable length, battery bank capacity, overcurrent protection, grounding, and the vessel AC distribution layout.

Electrical and system integration

For a boat with shore power and generator input, the MultiPlus-II can manage charging while keeping AC loads supplied through the main output. The PowerControl setting lets the system respect a limited pedestal or generator capacity, which is useful at marinas with smaller shore service or when running from a compact genset.

VE.Bus support allows the unit to become part of a broader Victron power system. With a GX device, owners can view system status locally or remotely, adjust settings, and monitor battery and AC power behavior through the Victron monitoring ecosystem. An optional external AC current sensor can be used for extended current sensing and energy management in supported installations.

Use cases on board

This model fits boats that need a single inverter/charger to handle larger AC loads, charge a 12V battery bank, and manage changeover between shore power, generator power, and inverter power. It is a strong match for cruising boats, fishing boats, and liveaboard systems where AC power reliability and battery charging control matter every day.

Because it includes a second AC output, it can help separate loads that should remain available from loads that should only run when external AC power is present, such as a water heater or other equipment that should not pull down the battery bank at anchor.