Comparison Between WatchMon 4 and WatchMonPlus

What are the Differences between WatchMon4 and  WatchMonPlus (WM5 or WM7)

Centralised or Decentralised

WatchMonPlus is centralised, this means that the cell monitoring is on the supervisor board meaning it is generally simpler wiring.  We have the WM7 version for 24V systems (that allows between 6-10 cells to be monitored) and WM5 version for 48V systems (that allows between 10-15 cells to be monitored)

WatchMon4 is decentralised, which means that the Supervisor and cell monitoring are separate.  The cell monitors are placed on the batteries and wired back to the WatchMon4.   As they are separate there is more flexibility in how many are wired up and how they are configured.  This gives you the ability to vary your system in a more flexible way allowing anything from monitoring a single battery to 250 cells. 

Cost and Ease of Use

WatchMonPlus is lower in cost and has fewer parts, therefore it has fewer things to go wrong once you have the wiring correct. 

Confirmation of Wiring Success

WatchMonPlus uses TestMon to verify that the wiring is correct before connecting your battery to the WatchMon, easy to use and simple to install.

WatchMon4 uses the Network Test   If the software of the Network test does not pass, you will need to check the wiring each wire until you find your problem, you cannot proceed until you get a pass.

What Batteries are able to be Monitored by each WatchMon

WatchMonPlus is more flexible here as it can deal with Shared Loom batteries, such as Tesla, Chevy and Fiat and also extends the voltage range allowing LTO batteries to be monitored. ( Note:  LTO due to the lower voltage per cell the WM5 would be 24V system and WM7 a 12V system)

The WatchMonPlus can also be wired up to all the other batteries that WatchMon4 is capable of monitoring.  

The WatchMon4 can do 4s, 16s or 18s configurations which WM5 cannot achieve but to this  you would also need to prepare your own balancing wires.

WatchMon4 would requires a cell monitor per cell in series, LeafMon for use with Leaf cells, BlockMons for use with Prismatic cells and LongMons for others.  

Note that WatchMon4 is not suited to OEM shared loom batteries.


WatchMonPlus has 3 external temperature sensors that can be placed around the battery pack to measure cell temperature.  

WatchMon4 relies on the temperature sensors on the cell monitors themselves so has one per cell monitor. 


Any expansion board, SOC% sensor, inverter or charger is compatible with both WatchMon's 

Balancing Power

WatchMon4 is able to balance 28.8Ah per cell per day.

WatchMonPlus is able to balance 6Ah per cell per day.   

Typically, the daily balancing requirement is between 100mAh and 1000mAh. This will depend on the battery cell age, chemistry and configuration. 

Balancing power beyond this level is useful to have in reserve for the initial balance and any minor fault or reconfiguration event but not every day.

If the initial cells are seriously out of balance and a large pack do some manual balancing to reduce the time for this first balance.


Why would I choose a WatchMon4?

  • If configuration outside of 6-10s or 10-15s limits
  • If battery pack requires higher balancing power
  • have existing cell monitors that wish to reuse
  • Ideally suited to large format prismatic cells

Why would I choose a WatchMonPlus (WM5 or WM7)?

  • Suitable for OEM batteries such as Tesla, Fiat, Chevy etc.
  • Suitable LTO batteries therefore requiring wider voltage range
  • Able to be used for most popular Lithium cells 
  • With MultiMon MM8 can be used in multi-string parallel or higher voltages in series. 
  • Simpler installation
  • Better value with the same functionality as WM4
  • All in one solution, fewer things to go wrong.

Why is WatchMonPlus still in beta?

We have had some systems running since July 2019 so why are we still in beta?  Well, being in beta allows us the option to push out more frequent updates if required.  It is likely beta will stay in place until after our WatchMonPlus slave board, MultiMon ( MM8), is out and had a few months being used.  This will give us the chance to discover any issues and address them.  MultiMon will allow multistring for the WMPlus and/or higher voltages to be achieved.

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