MultiMon MM8 - FAQ and How-to guides

MultiMon MM8 (Mates) is the satellite cell monitoring module for WatchMonPlus WM5.

Typical wiring diagram

Is it suitable for me?

  • Each MultiMon monitors between 10 - 15 cells in series.
  • Cell voltage between 0.5v and 5v.
  • Ensure that the battery pack cannot be pulled apart in cell groups as this risks the BMS being damaged whilst connected (i.e. twin 7S being separated).
  • The supply power must be fully isolated from the accessory circuit.
  • Can handle supervisor consumption of 1 Ah/day (for 48v) when running WiFi connectivity (~2W).
  • The size of the battery connected to the MultiMon should be as similar as possible to the Master WatchMonPlus so that when charging and discharging they reach full and empty together.

What can I do with a MultiMon (MM8) that I can't do with just a WM5

  1. MM8 allows you to expand your system by using Multi-String on extra banks of batteries with your WatchMonPlus WM5 as satellites doubling/tripling or more of your battery banks.
  2. MM8 allows you to expand your system into a higher voltage.  Do you want 96 V or more?  

Wiring is the same for WatchMonPlus and MultiMon MM8

This is a video showing the process of preparing balancing wires for the WatchMonPlus and MultiMon

Note:  ALL wires on the same MultiMon need to belong to the same battery bank.

Please let us know if you need an extra TestMon.


1.  Configure up WatchMonPlus WM5 first, as required.

2.  Prepare wiring loom for MM8 (Note wiring is same for WatchMonPlus WM5 and MM8)

This is a video showing the process of preparing balancing wires for the WatchMonPlus and MultiMon

3.   Test the MM8 Wiring using your WatchMonPlus WM5 TestMon

Whenever altering the wiring, unplug and take extra care before plugging in any of the connections. Make sure to verify with the TestMon again and revisit the commissioning sequence has not introduced any mistakes.

Please let us know if LTO batteries are to be used as TestMon is geared to LiFePO4 or Li Ion chemistry.

The TestMon is Included with WatchMonPlus orders if you need an additional one let us know.

4.  Plug in all three temperature sensors and place in relevant locations around the battery.

5.  MM8 WatchMon Toolkit setup

  • Please ensure the number sequence given to the WatchMonPlus and MM8 do not clash and are sequential.
  • Only one WatchMonPlus or MM8 is plugged into the computer at any one time.

  • 6.  Wire up the supply power pins.  

    Note:  It must be fully isolated from the accessory circuit.  A plug pack and daisy chain is acceptable.

    7.  Wire up the CANbus

    The MM8 uses CANbus to communicate with the WatchMonPlus WM5.  Multiple MM8 can be used and connect back to the WatchMonPlus WM5 in a daisy chain manner as shown below

    Remember, a resistor is required at either end of CANbus chain.  The terminating resistor supplied with the WatchMonPlus WM5 is suitable and can be used at the end of the chain on the last MultiMon MM8.

    Notes for wiring:

    • Create CANbus wiring from the Master to the last satellite in the sequence with a 120 Ohm resistor at each end
    • Twisted cable is used as per other CAN interfaces
    • The Inverter usually has a terminating 120 Ohm resistor built in to the inverter, hence handles one end of the termination
    • Our Master WatchMonPlus is next in the sequence.  If not communicating via CANbus the resistor needs to be on the WatchMonPlus
    • Note CANbus plug with resistor included with WatchMonPlus.  This can be swapped to the end of sequence MM8 if CANbus to inverter is used
    • Next connect the CANbus from the WatchMonPlus to the first MM8
    • Continue connecting in a daisy chain CAN high and CAN low till all your MM8 are connected,  The last one in the daisy chain requires a resistor to signify the end.

    8.  Post Install Balancing Verification Procedures:

    • Within the software, adjust the bypass voltage parameter to a value below the existing voltages
    • Commit the change to the supervisor
    • Visually check that each balancing Red LED works odds / evens
    • Monitor that the heatsink temperature increases whilst balancing
    • Within the software reset the bypass voltage parameter back to its original target
    • Commit the change to the supervisor
    • Visual check that the supervisor is no longer balancing.
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