BMS central processor that watches the individual CMU cell monitoring units and provides supervision functions.  The supervisor is able to notify a remote system(s) of the battery state and when required, trigger evasive action to prevent damage to battery pack.

More details and installation procedures here WatchMon4 FAQ. or Quick Start Guide

Software installation guide

Why do I need a starter kit not just the CellMons or WatchMon

The supervisor is not available individually by default except for those that have experience in ordering our products. Starter Kits ensure that you obtain all the necessary components to suit your application. If you have questions and are looking for the appropriate Starter Kit, please contact us, we can then assist you in making the right selection.

Refer to the FAQ on How to help us help you


  • ESP32 more powerful than WM 1
  • Data logging of key metrics for 10 years
  • Clock with backup battery
  • Optional over the air (OTA) upgrades to firmware
  • Upgrades firmware via USB
  • Secure web encryption to allow SSL link when connecting to optional cloud portal via MQTT.
  • Prevent all outputs from resetting when the processor firmware is updating (no transient on/off/on)

BMS Module Connectivity

  • Serial link to SoC% current sensor module
  • Serial link to isolated CellMon modules 

Remote Communication

  • WiFi connectivity (normal, disabled, or read only)
  • Can-Bus communication port to remote systems
  • Modbus rs485 link allowing connectivity to inverters without canbus
  • Optional blue-tooth connectivity (future enhancement)

Built-in input and Output Control

  • Two (2) onboard FET outputs 4A with 8A inrush 
    • e.g. remote circuit breaker trip + fan
  • Two (2) onboard input
    • e.g. circuit breaker trip sensor

Expansion Board Compatible

  • Only required when additional functionality is required
  • 26 pin IDE ribbon connector
    • 5 Digital inputs
    • 2 Analogue inputs
    • 1 Pulse counter input
    • 8 Digital outputs  (4 FET + 4 Relay)
    • 2 Digital output PWM
    • NeoPixel LED control

Power Input

  • Built-in 8v to 65v DC-DC supply
  • Handle automotive transients

Ease of Use

  • Pluggable screw terminals to simplify installation, allowing pre-made cables for both shunt and cellmons
  • Relocation of onboard temperature sensors away from heat sources to have better representation of ambient conditions
  • Finger guard cover clip slots, more coming soon
  • Intuitive screw terminal labelling to reduce need to check documentation


  • Length 107 mm x Width 55 mm 

WatchMon4 requires the Latest release of WatchMonToolkit

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