How to Control a Victron GX with a WatchMon

Victron have advised us that all their GX models are the same for the BMS communication layer.

  • Victron Color Control GX - CCGX
  • Victron Venus GX
  • Cerbo GX
  • MultiPlus-II GX (built in)
  • EasySolar-II GX (built in)

Here are the steps to configure the Victron Color control GX to the WatchMon Supervisor.

The same methods can be used to any of the other  GX device variants to the WatchMon Supervisor.

CAUTION: The example below has values shown for a demo LiFePO 4 cell pack, please ensure that you adopt values suitable to your application and comply with the battery suppliers recommendation. 

Step 1 - Install communication cable to CAN port on the supervisor.

For newer WatchMon supervisors these are 3 pin (note 120 Ohm resistor) shares CANbus High and CANbus Low

WatchMon4 / WatchMon5 and MultiMon8

For older WatchMon with 4 pin CAN see below

Only for WatchMon4

Step 2 - Install communication cable to Victron GX canbus socket (extract from manual)

Plug the GX side of that cable into one of the VE.Can sockets on the back of the GX. Plug the other end into the battery. Then, plug a VE.Can Terminator in the other VE.Can socket on the GX. 

Custom Cable pinout for GX

Function VE.Can RJ-45 WatchMon Colour Pinout
(Type 568A)
GND Pin 3 CAN isolated ground
only connect if effected by transmission noise
White / Orange
CAN-L Pin 8 CAN low Brown
CAN-H Pin 7 CAN high White / Brown

For reference, here’s an Ethernet plug diagram. Be aware that some Ethernet Cables may vary as there are 2 common wiring colour standards. Make sure that you inspect the plug on the Victron side and follow the wiring colour to the BMS terminal

To make up the custom Ethernet Cable for the GX properly, you should use a proper crimper and fresh RJ45 male connectors.  Label both ends of the cable and install it.

Outline above is for the TIA/EIA T568A straight though connector outlined in blue below

Step 3 - Navigate to Hardware, then Integration tab.

Step 4 - Select Canbus protocol to "Victron GX" and Save (previously labelled Victron ColorControl GX).

Step 5 - Navigate to Control Logic, then Charging tab.

Step 6 - Adjust the Charging control logic to suit the application.


  • In newer versions of the software
  • Limited power must be enabled.
  • Cell Hi Cutout should be above the CellMon bypass voltage threshold as a safe guard target.
  • Low power current should suit the bypass capability of CellMon.
  • When the bypass current is above Initial will trigger the system to low power.
  • When the bypass current for all cellmons is above Final the system will complete charging cycle.

Step 7 - Navigate to Hardware, then CellMon tab.

Step 8 - Adjust the CellMon bypass voltage to suit the application.

Note: Make sure to "Device Sync" the changes to the CellMons.

Step 9 - Navigate to Control Logic, then Remote tab.

Step 10 - Adjust the remote charging target to suit the application.


  • Scaling must be 10 for both voltage and current.
  • Low power must be enabled on charging tab.
  • Low power current should suit the bypass capability of CellMon.
  • Charger voltage target needs to be sufficient for all cells to reach bypass threshold.

Step 11 - Adjust the remote discharging targets to suit the application.


  • Scaling must be 10 for both voltage and current.
  • Do not run low power mode on discharging tab.
  • Control logic discharge voltage cutout should match the remote target.

Step 12 - Navigate to Telemetry, then Live Stats to observe system operation.

Step 13 -Within Victron software - VEConfigure settings

13.1 General tab
  1. Check “Enable Battery Monitor”
  2. Enter the battery capacity in Amp Hours ( i.e. 120.0 Ah)
  3. The other parameters ( “State of charge when bulk finished” and “Charge efficiency”) can be left to their default setting. They are not used in this setup.

13.2 Charger tab

Parameter Setting
Battery type Lithium
Charge curve Fixed
Absorption voltage 60.75 V
Float voltage 60.00 V
Absorption time 1 Hr

Note: make sure to double check the float voltage after completing Assistants, and if necessary set it back to 60.00 V.

This needs to be adjusted to match the BMS operating targets.

13.3 ESS (Energy Storage System) Assistant

Select the fourth battery type:


  1. Do not change the dynamic cut-off values, they have already been set correctly after selecting the lithium battery type.
  2. Sustain voltage: 50 V
  3. Same for the restart offset: do not change that.

Step 14. Within Victron software - device configuration

  • Select the  CAN-bus BMS (500 kbits/s) CAN-profile in the Venus device. Menu path:  Settings → Services → CAN-profile. Note that this changes the function of a VE.Can port: it is not possible to connect both VE.Can products and a BMS battery together on a Color Control GX. 
  • Select CAN-bus BMS (500 kbit/s)
  • After properly wiring and setting up, the BMS the ESS will be visible as a battery in the device list:
  • The Parameters option within the battery page shows the actual battery charge and discharge limits:

Frequently asked Questions

  • Can the BMS send the SoC% to the Victron Inverter?
    • Yes
  • Can the BMS send the cell statistics of Highest and Lowest cell?
    • Yes, when using the Victron canbus profile (from software release 2.16 onwards)
  • Can the BMS ramp down the charging rate towards Full or Empty?
    • Yes, adopt the correct Control Remote configuration  (from software release 2.17 onwards)
  • Why does the Remote Actuals only show NS and not values from the Victron equipment?
    • Not all the Victron product transmit back the optional actual values. Hence we cannot display these values if they are not transmitted from the GX.
    • The communication is not at fault, verify that the GX is sending the heartbeat RX timestamp to confirm communication is functioning properly
  • Can the BMS read the SoC% from Victron equipment instead of our own ShuntMon module.
    • No, the Victron canbus protocol does not send these details, it expects the BMS to send it to them.
  • Can you run both a Batrium ShuntMon and Victron Shunt in series.
    • Yes, if desired
  • Can you run without a Batrium ShuntMon?
    • Yes, however will limit the functionality since the BMS does not know the SoC% can cannnot adjust its recommend charging and discharge targets 
  • Can you bolt the ShuntMon electronics to the Victron shunt block?
    • Not recommended, only possible if 50mV for 500A, 1000A or 2000A

Note:  Please  ensure  that  the  firmware  for  all  Victron Energy  equipment  is  up  to  date.  Details  on how  to  check  firmware  versions  and  perform  updates are  available  from  the  manufacturer directly.

Additional useful screens to monitor:

  • Node Chart
  • Charging logic control 
  • Remote logic control
  • Live Statistics telemetry
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