Basics of the Inverter/Generator coupling and the "Start and Stop" function with Victron Energy products

Basics of programming the inverter and the functions related to the generator on VE configure:

The power coming from a generator is usually more variable than the power coming from the network, the Inverters are very sensitive to this type of behavior and if the input power doesn't meet certain requirements, the Inverter doesn't accept the input power and it doesn't synchronize.

The inverter-generator coupling therefore requires some precautions:


The first choice to face is the purchase of a suitable generator, there are many generators on the market but not everyone are particularly suitable to "talk" with a Victron inverter.

It's always better however for this kind of applications to choose a generator with AVR control (auto voltage regulation) that, unlike generators with an internal inverter which operate independently of the load as they are electronically controlled and not mechanically, generators with AVR stop working if the load becomes excessive.


How to size the generator?

It depends on the inverter you own, Victron recommends these inverters for different generation powers:


It's important to note that, once the inverter is installed, the synchronization phase can last a few minutes and therefore the coupling will not be instantaneous.

Let's see what are the steps to follow on the VE Configure software provided by Victron to correctly configure the Inverter:

Once the program has been started and the inverter has been found as a target, open the "Grid" page and deactivate the check on "UPS function" as shown in the figure, if this function is active you will not be able to connect the generator.

 It's also necessary to activate the "Accept wide input frequency range (45-65Hz)" function so that it's possible to accept generator instabilities in terms of frequency, if the generator is extremely stable, this option can be avoided.

 VE Configure also allows to set the values ​​for which the inverter disconnects and then reconnects for higher or lower voltages, some values ​​are automatically suggested by the program, however it's advisable to correct these values based on the generator model you have.


If the system is not off-grid and there is a connection on the public grid, after selecting the correct country and norm (as in the figure) it's possible that the generator requests to deactivate the LOM (Loss of main detection), you can find more information at this link:


If you have a low power generator it will probably disconnects in case of high currents due to the starting of some machine present on the Inverter loads (AC out).

On the "General" page of VE Configure you can select a function called "Dynamic current limiter", whit this function the Inverter "power assist" will satisfy the starting loads using the batteries and not the generator that will remain in operation without turning off ensuring a lower but constant load (see figure below).


The Multiplus inverters are very powerful in terms of charging current, so it's often necessary to limit the input current if the generator fails to provide such power, a simple rule allows you to calculate which is the optimal current for your generator:

Just calculate the required current referred to 80% of the nominal power of the generator, for example: if you have a 5kVA generator that typically generates 4kW of power, 80% will be 3200W and the current to be set will be 3200W / 230V ie 13.9A, for security you can enter a value of 13A in the "AC1 (or AC2 in the case of an Inverter "Quattro", as it depends on where the generator was connected) input current limit ".

A last precaution is necessary: ​​some generators produce a waveform in their output that makes it difficult to make a correct charge of the inverter batteries, to avoid this problem you can check the "Weak AC input" box on the "Charger" page.

The disadvantage in using this function is that the conversion efficiency will not be close to 1 as for a normal inverter operation but around 0.8, so it's advisable to activate this mode only if the generator actually creates this kind of problems. (see image below)



Introduction to the Start/Stop function:


One of the most used functions of Victron and Studer products is the automatic start of the generator in case of excessive discharge of the batteries.

This function is often used in off-grid systems because it saves time and money by avoiding the need to manually turn on the generator whenever is necessary.

In this article we will investigate, as far as Victron-branded inverters are concerned, how this process works and how the machines can be programmed to work in the right way.


Control methods:

The first question to ask is: what control device should I use?

If you use Victron products there are three cases:


1. Use of the Venus Devices such as Venus GX or CCGX:
If one of these devices is present, its generator start / stop mechanism should be used, as it's the most complete method provided by Victron. In addition to the basic start / stop functions based on the state of charge of the batteries or the measurement of their voltage, this system also has some advanced functions such as the possibility to program "silence" time intervals (in which the generator it's not started in any case) or the start of automatic tests.

2. Use of the BMV (Battery Monitor):
If you have this device you can use it to send a signal in case of low state of charge or low voltage of the batteries.

3. Using the relay inside the inverter (Multiplus or Quattro):
The Multi, Multiplus, Quattro and Easysolar inverters (that are all the Inverters of the VE.Bus family), also have an internal relay for this operation, this relay can be programmed through a special Assistant (wizard) on the VE Configure software provided from Victron or through a special Virtual switch configuration.


It's also possible to make a combination of these configurations if you have more devices in order to make the operation more precise, just connect the signals coming from the different devices in parallel.


How to connect the generator with the three-wire interface:

All Victron products and devices have a single relay; normally it close to start the generator. If you have a generator that requires a start impulse and a stop impulse, (such as Cummins/Onan generators) additional wiring is required. To start such a generator is the opening / closing contact must be converted into a start and stop pulse: when the contact opens, the "start" command is generated, while when the contactc close it generates the "stop" command, note that this solution must be used only on generators that have their own control panel and that stop automatically in case of loss of oil pressure or signals coming from other sensors, or in other words: never connect this relay directly to the starter motor.


How to start the generator using a Venus GX or a CCGX:


The above mentioned devices have a programmable internal relay, here there are the steps to follow for a correct programming:


1. Wiring:

Connect the relay to the generator, the relay is placed in the back of the CCGX and is marked with the word "Relay", if you use a Venus GX you will notice two relays: only Relay 1 can be used for this function.

As regards the connection on the generator side it's advisable to check its manual as it varies from model to model.


2. Activate the Start / Stop function:

Go to Settings / Relay and set the Function parameter to "Generator start / stop",

once this function is activated all the settings will be enabled and will be found in the main menu in: Settings / Generator start and stop


3. Generator start / stop Main page: From the main menu select Settings / Generator start and stop


  • Generator state: Current generator status.
  • Error: Description of the error.
  • Runtime: Period of operation of the generator since the last start.
  • Total run time: Total operating hours from the first start.
  • Time to next test run: If the "test run" mode is enabled, the time remaining at the next test run is indicated.
  • Daily runtime: History of generator operation in the last 30 days.
  • Settings: Other settings and functionality.

4. Settings:


  • Conditions: See "Conditions" chapter
  • Minimum run time: allows the generator to reach the optimal temperature once started.
  • Detect generator at AC input: This function activates an alarm if no power is detected at the inverter's AC in terminals, the purpose is to report a wide range of possible problems such as lack of fuel or technical problems of the generator.
  • Quiet hours: See "Quiet hours" chapter
  • Reset daily run time counters: Delete the operation's history of the last 30 days.
  • Generator total run time: Changes or deletes the history and total count of operating hours since the first start.

5. Conditions (Parameters and conditions on which the generator autostart depends): To reach this page, follow the route: Settings → Generator start and stop → Settings → Conditions


  • Battery monitor: Select the device dedicated to monitoring the batteries.
  • On loss of communication: If there is a lack of communication, you can decide whether to block the generator, start the generator or leave it running
  • Do not run genset when AC1 is in use: This function is ideal for "Quattro" inverters that have two AC inputs (one for the electricity grid and one for the generator), enabling this function makes possible to start the generator only in case of lack of energy from the electricity grid.


The following parameters (as in the image) can be set to active or inactive depending on which parameter you wish to control for the generator start. Each option requires special thresholds to be set manually.

6. Automatic Periodic "Test run": This function allows the generator to be started periodically as a test run in order to monitor its operation and avoid prolonged shutdown periods.


It's possible to set the duration of the interval, the interval between a "test run" and the next and other parameters.

7. Quiet Hours (hours of silence):


This function allows you to define time intervals in which the generator is not started so as not to cause noise in certain time slots.

In any case, it's possible to establish conditions for which, if absolutely necessary, the generator still starts even in the hours set as "silent hours".


How to start the generator using the BMV 700:

It's possible to use the relay inside the BMV700 to start the generator if the batteries fall below the preset voltage threshold, to do this it's necessary to put the "relay mode" in the settings of the BMV700 to "CHRG" (Charger mode). In this mode the relay closes when the state of charge falls below the value of setting n. 16 (discharge threshold) or when the battery voltage falls below the value of setting n. 18 (low voltage relay). The relay opens when the state of charge is higher than the value of setting n.17 (relay end of charge status) and the battery voltage is higher than the setting n. 19 (relay low voltage end).

For the BMV700 settings, refer to the manual that can be downloaded from the Victron website at the following link:


How to start the generator using the relay inside the inverter:

As mentioned earlier there are two different methods to start the generator using the Inverter internal relay: 

1. Use of the Virtual Switch: The relay to be connected to the generator is indicated on the manuals as "Alarm Relay", this block is detachable and then can be removed to facilitate wiring and then reattach it. There are 3 contacts from left to right respectively: Normally closed (NC), normally open (NO), Common (COM). Here we will explain how to start the generator with the Virtual Switch mode that can be activated by the VE Configure program (you can download it from the Victron Energy official website).



Here there are the contacts for the Multiplus II, from left to right: normally open (NO), normally closed (NC) common (COM).


On the Multi 500, 800, 1200 and 1600 Inverters the contacts are from left to right the following: Common (COM), Normally closed (NC), normally open (NO)


As far as programming is concerned, the steps are the following:

1. Select "dedicated generator control" in the "Virtual Switch" - "Usage" page.


2.Configure the parameters related to the loads and types of batteries that you have on the "Generator control" page.

NOTE: those shown in the figure are only examples, configure these parameters carefully consulting the product manuals.



2. Use of the Assistant on VE Configure: In the Assistant section there is an automatic configuration to set the generator start mode: just follow the steps indicated and enter all the required parameters.