Victron MultiPlus-II 12/3000 120V Inverter/Charger (UL 458)

The Ultimate All-in-One: Victron MultiPlus-II 12/3000 Inverter/Charger

The Victron MultiPlus-II 12/3000 (MPN: PMP122305122) is an advanced, multifunctional inverter/charger that elegantly combines the proven features of the MultiPlus and the MultiGrid into one UL 458-certified unit. Designed for 12V DC systems, it delivers 3000VA of 120V AC power while integrating a robust 120A battery charger and a 50A transfer switch. With built-in anti-islanding and an external current transformer option to optimize self-consumption (max. 32A external current sensing), this unit acts as the key component in Victron Energy Storage Systems (ESS), offering seamless integration with MPPT Solar Chargers or Grid-tie PV inverters.   

PowerAssist and Uninterrupted AC Power (UPS)

The MultiPlus-II utilizes Victron’s innovative PowerAssist technology to prevent the overload of limited AC sources, such as a generator or shore power connection. It first automatically reduces battery charging to avoid an overload, and then seamlessly boosts the output of your AC supply with power drawn directly from the battery. In the event of a grid failure or disconnected shore power, the built-in UPS function automatically takes over the supply to connected loads in less than 20 milliseconds, ensuring sensitive electronics and computers operate without disruption.   

Scalability and Remote Monitoring

When paired with a GX device (such as the Cerbo GX), the MultiPlus-II offers limitless control and remote monitoring. Boaters and off-grid users can manage their system locally via LAN or remotely from anywhere in the world using the free VRM app and portal.

Technical Specifications

• Brand: Victron Energy
• Model: MultiPlus-II 12/3000 - 120-50 - 120V   
• Part Number (MPN): PMP122305122   
• Input Voltage: 12V DC   
• Output Voltage: 120V AC   
• Continuous Power Output: 3000VA   
• Battery Charger Capacity: 120A   
• Transfer Switch Rating: 50A   
• External Current Sensing: Max 32A option available   
• Certifications: UL 458   
• UPS Transfer Time: Less than 20 milliseconds   
• Monitoring: Compatible with GX devices (e.g., Cerbo GX) and VRM app/portal  

FAQs

What is the difference between the MultiPlus-II and the original MultiPlus?

The MultiPlus-II combines the functions of the standard MultiPlus and the MultiGrid. It includes all standard features plus an external current transformer option for optimized self-consumption (max 32A) and built-in anti-islanding for advanced ESS integration. (Note: For a short period of time, this product was called the MultiGrid-II).   

How does the Victron MultiPlus-II PowerAssist feature work?

PowerAssist prevents the overload of a limited AC source like shore power or a generator. First, it automatically reduces battery charging to avoid an overload. Second, it boosts the output of the generator or shore supply by supplementing it with power taken directly from the battery.   

Can the Victron MultiPlus-II act as a UPS (Uninterruptible Power Supply)?

Yes, the MultiPlus-II features a UPS function that automatically takes over the supply to connected loads if the grid fails or shore/generator power is disconnected. The transfer happens in less than 20 milliseconds, keeping computers and electronics running without disruption.   

What is the best way to wire the AC terminals on the MultiPlus-II to prevent overheating?

As frequently discussed by users and installers in DIY and Victron community forums, the push-in/clamp-style AC terminals on the MultiPlus-II require precise installation. To prevent the terminals from overheating or arcing under heavy load, it is highly recommended (and emphasized in updated Victron manuals) to use properly crimped wire ferrules and ensure adequate stripped length on all AC wire connections.

Why does my MultiPlus-II trip the GFCI outlet when plugged into shore power?

Users often note on forums that when plugging the MultiPlus-II into a GFCI-protected shore power outlet, the shore breaker may trip when the charger initiates. This is typically due to the unit's internal ground relay bonding the neutral and ground during startup or inverter mode, which the sensitive shore GFCI interprets as a ground leakage fault. Always ensure your RV or boat is wired with proper, separated grounding practices according to ABYC/NEC guidelines when using an inverter-charger.