CellMate-K9 Overview (3 to 16 in series)

CellMate-K9 is suitable for a shared wiring harness that can be used in conjunction with the WatchMon CORE supervisor.


  • 3s to 16s enabling  monitoring of 3s - 12V systems all the way to 16s 48V systems
  • Two or more CellMate-K9 can be daisy chained to create a higher voltage battery.
  • Multistring is possible using multiple CellMate-K9, e.g. one per CellMate-K9 per 12V, 24V or 48V bank
  • Many CellMate-K9 can be daisy chained to grow your system.
  • Requires with WatchMon CORE supervisor.
  • Separating cell monitoring from the supervisor for a more robust solution.
  • Able to have Fan mounted to enhance balancing
  • Pluggable connectors for easy wiring.
  • Enable second life use of existing balancing connectors in OEM packs like Tesla, Nissan Leaf, Chevy Volt, etc. that use "shared" wires between each cell in series (recommended to attach 3A fuse inline as close to battery as possible to protect cabling).
  • cell monitoring from 0.50V to 5.50v with 0.001v resolution
  • configurable to suit LiFePO4, Lithium-Ion or custom chemistry
  • Auto-Level (balancing) function at 500mA with activity LED on each cell.
  • Capable of 6 Ah/day balancing adjustment for each cell 
  • user configurable presets and controls
  • 4 external temperature sensors
  • LEDs showing operating status and communication 

Inside the box:

  • 1 x CellMate-K9
  • 1 x Din-rail holder
  • 4 x Temperature sensors
  • 1 x 5 pin 15cm connection cable


  • Length 107 mm x Width 86 mm

 Optional Extras:

  • 16 series TestMon to suit CellMate-K9
  • Set of 18 in line 3A fuses

Balancing Power

Cellmate-K9 is fabricated with 4 Ohm resistors to suit LiFePO4, Lithium-Ion or custom chemistry. This results in an Auto-Level (balancing) function of approximately 500mA achieving  more than 6 Ah/day balancing adjustment for each cell. The system operate in a four cycle sequence of 5 second intervals. This allows for approximately 50% duty cycle between adjected cells in series to not impact cell voltage sensing or exceeding wiring or fuse ratings. When balancing is required the four stages are as follows of ODDS, EVENS, resting, then sensing and repeat. Ensure that the balancing wires are dedicate for this function and do not share any circuit with other devices. If you run other devices these need their own circuit, take care to consider this for the power of other equipment like supervisor which should have their own cabling. Take care to not have shared wiring with adjacent CellMate-K9 if higher voltage series as these will impact each other.

Mounting a Fan

CellMate-K9 has been designed to allow a 60mm Fan to be mounted to enhance balancing performance if customer desires. 

Fan and standoffs not supplied.

  • M3 screws to mount Hex standoffs to the CellMate-K9
  • Standoffs should be 30mm in order to clear the heat sink.
  • Fan hole centres are 60mm apart.
  • Fan power can be triggered by the logic of the WatchMon CORE 
  • Adopt any of the Relay/SSR to switch the fan power ON.
  • Fan selection and voltage is you decision (i.e. 12, 24, 48, 5V etc).
  • Fans speed only needs a light breeze (small airflow), not a gale (high breeze). Do not run a high volume air flow fan it will not help, will be noisy, shorter lifespan and waste power. The smaller the better. With just a light breeze the temperature will drop from 60ºC to less than 10ºC above ambient when running.
  • Always consider where the heated air flow is sent as capable of more than 20W combined. If within an enclosed box containing the battery cells this heat maybe desirable or not, either way consider where the air vents.
  • Fan power if 5V must not be powered from the onboard 5V DC-DC of the WatchMon CORE
  • Except for the initial commissioning (combining cells), the balancing should not be operating for any extend period of time except if cells have no defects.

Cable Specification

Cable joins the CellMate K9 to WatchMon CORE and/or CellMate K9 to additional CellMate K9s in a daisy chain with terminator on last K9 in the daisy chain.

Communication network for Single CellMate-K9 

Communication network for Multiple CellMate-K9 

Note: Each cable can be 1.5m, capable of up to 20 CellMate-K9 monitoring modules for a CMU network. However will require external 5v power beyond 6 units. Contact us for more details if consider this application. Adopt twin twisted pair cable with sufficient core to ensure no voltage drop 22-26AWG tinned and multi-strand. Cell can be in series, parallel or multi string as each cell monitoring module is fully isolated from CMU port. Relocate Loop back to the end of the network.

For extra 5V power to the supervisor consider the following booster power to run the system, this power can be injected to the CMU port pin for 5V and GND for the CellMate-K9, ensure that the CMU ground pin to the supervisor is connected for the communication to work.

Isolated DIN Rail Mount DC/DC Converter, Railway, 4:1, 15 W, 1 Output, 5 V, 3 A
Input Voltage DC Min 18V Input Voltage DC Max 75V

Wiring from battery - fused at cell NOT BMS

Note: ensure fusing within 15cm of cell terminal or closer if possible. Ensure wiring gauge is appropriate and avoid using over-rated cables. Consider putting into a protective cover when combining multiple cables.

Cell terminals on K9 for 16 cells in series

Cell terminals on K9 for 14 cells in series

Cell terminals on K9 for 12 cells in series

Cell terminals on K9 for 8 cells in series

Cell terminals on K9 for 7 cells in series

Cell terminals on K9 for 3 cells in series

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