This article is about setting up parallel or split phase systems using the MultiPlus or Quattro inverter chargers. A parallel configuration means you are using more than one MultiPlus or Quattro to increase the total power available.  A split phase system means you are putting two identical units beside each other to work in 180 degree opposite phases; two 120 volt units can make 240 volts total and the result is a 120/240 volt system. Before you get too far along building a split phase system you might like to consider another option using an Autotransformer instead. That option is covered in my blog post: Generating a 120/240 Volt split phase power supply from an inverter 

The principal resource for setting up a system like this is the Victron Energy online manual, Parallel and three phase VE.Bus systems  For professional installers with access to the Victron Professional website there is a detailed online video but this is not made available to the general public due to the highly technical nature of the project. What I am covering below is aimed at parallel or split phase systems only, we will save three phase systems for another day.  It is recommended that this setup be done by a professional or by someone who has done their homework with appropriate diligence and has a solid grasp of what is required.

The starting point for a parallel or split phase system is that all the devices must be identical and running the same firmware. The best way to ensure the firmware is the same for each device is to update each unit individually to the latest version using the Victron Connect App.  Using this App simplifies the process because if you have the latest version of the App it automatically includes the latest version of all available firmware. Before you start just make sure your App is up to date by downloading the latest version for Windows or Mac from the Victron website. Once you connect to the MultiPlus or Quattro with the App using the Mk3 USB Interface it will prompt you to upgrade the firmware if a later version is available.  Note that once you update the firmware all the settings will be lost and the units will be set back to default, so if you need to save a copy be sure to do that before you do the update. This first part of the programming is the only part that can be done with a Mac, the other two programs we are going to use later in the procedure require you to use a PC

Next the wiring should be set up in such a way as to deliver the same voltage to each device.  That means for the DC wiring that the cable lengths and sizes should be identical and the units must be using the same battery bank.  The online manual goes in to this in more detail.  The same principal applies to the AC wiring, they want to duplicate everything between the units as much as possible.  The manual is very specific that a continuous unbroken negative connection must join all units. Don't put an on-off switch in the negative line that could separate the units otherwise some of the data wiring would try to become the negative connection and all the circuit boards would be fried.  Chapter 4 of the book Wiring Unlimited goes into more details.

Wiring Unlimited

To work together the units must be connected together with VE Bus cables.  Because this is such a critical connection its best to use Victron Cables for this, my Blog Post Please use Victron VE Bus cables to hook up VE Bus equipment explains why.  To do the programming setup requires a PC and the Mk3 USB Interface     We will be using two programs to set up the system, both can be downloaded for free from the Victron website as part of a suite of tools known as the VE Configuration Tools

The first program, VEConfig, is used to program each unit individually for all charger settings including battery type, charge voltage and current, and any appropriate inverter settings such as low voltage shutdown, output voltage and frequency etc.   The settings for each unit must be identical.  Full details on how to do this are contained in my three part Blog Post Programming your Victron MultiPlus or Quattro with the VE Configure program  There is even a Victron Video that takes you through the steps. A screenshot from the program is shown below.



VE Config


The next program VEBusQuickConfigure is used to set up how the multiple units work together.  In the very first screen you get to decide how you want the units to work, the screenshot below shows the two options that we have been talking about, one for Parallel Systems and one for Split Phase systems.


VEBusQuickConfigure screenshot

You can try out the program in demo mode before you start, its very intuitive and once you have selected from the options below the next step is identifying which is going to be the Master Unit.  The program is quite old and refers to the Mk2 USB interface which is just an older version of the Mk3 USB.  When you get to the end the final screen looks something like this:


Along the way if you click on the wiring information box this note pops up: