When communication has been established, the Cerbo-GX can monitor and display pack/ cell voltage, current, temperature, state of charge (SOC) as well as any errors that may be present. If parameters are outside of a pre-defined safe range, the Cerbo can call on all devices in the system to reduce (or stop) charging, shut down / stop discharging, along with other measures required in order to protect the batteries.

Communication changes a GX device from a passive monitor into an active controller. The available features depends on the installed Victron components and their configuration. Victron inverter/chargers and MPPT Solar Chargers use their own internal charge algorithm when in stand-alone mode. This means that they determine how long to remain in Absorption, when to switch to Float, when to switch back to Bulk, or Storage. In those various phases they use the configured parameters set in VictronConnect and VEConfigure. When communication is established, the battery tells the rest of the system what it needs them to provide in order to properly charge and maintain the battery pack.

Cables

To establish communication with a Victron device, a special cable must be used. This cable uses RJ45 connectors but has a special pinout in order to get the proper data on the correct pins.

Pre-Made Cables

Cables that have been made ready to work out of the box are available form CurrentConnected here. We highly recommend checking these cables upon receipt to ensure they are labeled as “Victron-CAN”, otherwise an incorrect cable can lead to difficulty communicating.

Making Your Own Cables

Expand instructions for making your own cable can be found by clicking the arrow
The following table depicts the pinouts used on the Victron Cerbo-GX, as well as the CAN port of the SK48v100. When hand-making cables, we highly recommend confirming the pin configurations, as mistakes can lead to very difficult-to-troubleshoot problems and even potential damage.

Victron / SK48v100 Pinout Table
Function Victron Cerbo SK48v100
GND Pin 3 Pin 2
CAN-L Pin 8 Pin 5
CAN-H Pin 7 Pin 4

If you wish to make your own cable, use our pinout table which creates a cable that is bidirectional, meaning either end can be plugged into the Cerbo-GX or the battery while still preserving full functionality. When using the previous table or competitor’s cables, it will require certain ends be plugged into their corresponding devices.

Connector #1 Connector #2
Pin 1 Pin 1
Pin 2 Pin 2
Pin 3 Pin 3
Pin 4 Pin 4
Pin 5 Pin 5
Pin 6 Pin 6
Pin 7 Pin 7
Pin 8 Pin 8

Connection Port & Procedure

The communication cable plugs into the CAN-BMS port of the Cerbo-GX, and a terminator provided with the Cerbo-GX must be plugged into the empty port.

Verify the DIP switches of the master battery are set to address #1, ON-OFF-OFF-OFF and slave batteries are set to unique address as designated here.

Ensure all batteries are in the “BMS-OFF” state prior to installing the cable(s) as explained in the shutdown procedure. After the cable(s) have been installed, power up the system making sure to follow the proper start-up procedure.

Cerbo-GX Setup

Victron previously had a bug (fixed in the latest Cerbo-GX update) that causes a glitch where batteries stop charging at 52.4v (Around 30% SOC). Previously, in order to successfully utilize communications, a bug fix needed to be applied, however, simply updating to the latest firmware will fix this bug. If old firmware compatability is required, we have a full page detailing this process available here.

If the battery is not detected by the Cerbo:

  1. Ensure the cable is plugged in properly, and that a CANBUS terminator is inserted in the unused port
  2. Enter main menu and select “Settings”. Scroll down to the “Services” selection.
  3. Under BMS-CAN port, ensure CAN-bus BMS (500 kbit/s) is the selected protocol.

High-Voltage Alarms

The following is quoted from Victron’s documentation:
The ‘high voltage’ warning or alarm is not unusual on new batteries that are not yet balanced. To help the batteries balance quickly, keep the batteries fully charged until the errors go away. In an ESS system, set it to ‘keep batteries charged’, in an off-grid system the fastest way is to either charge / balance the battery before installation, or to fully charge with a generator if not enough solar is available to keep the batteries fully charged.

If you are unable to maintain the target voltage to balance the batteries without the ‘high voltage’ alarm occurring, you may need to enable and set the “Limit managed battery charge voltage” setting in the DVCC menu of the GX device. Reduce this voltage as necessary until the alarm stops. After sufficient time to balance the batteries, try increasing this value until it can be disabled again for normal operation.

Fallback Settings

In the event of a CANBUS communication failure, the parameters set within various devices such as inverter/chargers and solar controllers will be utilized in an open-loop configuration. It is highly recommended to set these devices to appropriate LiFePO4 settings as described here to prevent over/undercharging.