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.