signalk-rec-bms

Features

• Reads all available data streams from BMS and publishes to SignalK
• Supports WebSocket connection from the REC WiFi module with firmware >= SW164_2
• Supports serial connection directly from BMS
• Can set BMS settings when using serial connection
• Live status & settings page within SignalK

Notes

Tested with the 4 cell ABMS model only. Multi-unit series configurations are detected automatically but have not been tested beyond a single unit — proceed with caution if running multiple ABMS units in series.

Requirements

WebSocket connection (WiFi):

• A REC WiFi module with firmware >= SW164_2, which enables websockets

Firmware SW164_2

Serial connection:

• RS485 to USB adapter with 3v output. The REC-BMS serial chip is not powered internally and you must supply 3v to power it.

Dependencies

• npm package: ws
• npm package: serialport
• npm package: crc

Installation (choose one)

Use the SignalK application store (preferred)

Run the following command:

npm install signalk-rec-bms

SignalK Paths

All data is published under electrical.batteries.bms.* by default. The base path is configurable via the deltaPrefix plugin setting. Key paths include:

Path	Description
electrical.batteries.bms.voltage	Pack voltage
electrical.batteries.bms.current	Pack current
electrical.batteries.bms.power	Instantaneous power
electrical.batteries.bms.capacity.stateOfCharge	State of charge (0–1)
electrical.batteries.bms.capacity.stateOfHealth	State of health (0–1)
electrical.batteries.bms.capacity.nominal	Configured capacity (Ah)
electrical.batteries.bms.capacity.remaining	Estimated remaining (Ah)
electrical.batteries.bms.cellVoltage{N}	Individual cell voltages
electrical.batteries.bms.cellTemperature{N}	Cell temperatures (K)
electrical.batteries.bms.cellResistance{N}	Cell internal resistance (Ohm)
electrical.batteries.bms.bmsTemperature	BMS board temperature (K)
electrical.batteries.bms.minCellVoltage	Minimum cell voltage
electrical.batteries.bms.maxCellVoltage	Maximum cell voltage

Temperature values are published in Kelvin in compliance with the SignalK specification. Instrument displays that respect SK unit preferences will convert automatically to °C or °F.

Victron Cerbo GX / Venus OS

VenusOS claims all USB serial devices by default via its serial-starter service, which cycles through Victron protocols and prevents SignalK from accessing the port. The setup script creates a udev rule that instructs VenusOS to ignore your specific RS485 adapter, leaving it available exclusively for SignalK. The rule uses a zz- prefix to ensure it overrides Victron's default rules regardless of load order.

curl -o /home/root/signalk-rec-bms-venusOS.sh https://raw.githubusercontent.com/ofernander/signalk-rec-bms/main/venus-os/signalk-rec-bms-venusOS.sh && bash /home/root/signalk-rec-bms-venusOS.sh

The script will list your connected USB serial devices, you select which one is the usb to serial converter for your REC-BMS. Once complete, unplug and replug your RS485 adapter, then reboot the Cerbo device.

To uninstall: bash /home/root/signalk-rec-bms-venusOS.sh --uninstall or select the last option in the script menu.