Comparison of Individual CellMons (LongMon & BlockMon) and Central (CellMate-K9)

What are the Differences Between Individual (LongMons, BlockMons, & LeafMons) and Central (CellMate-K9) Cell Monitors?

Centralised or Decentralised

CellMate-K9 is Centralised, this means that the cell monitoring is generally simpler wiring. This model allows between 3-16 cells to be monitored for systems from 12v, 24v or 48V systems. Multiple can be adopted in a chain with up to 20 modules with a maximum of 250 unique cells.

The LongMons, BlockMons and LeafMons are Decentralised, which means that each individual cell has a separate monitoring module. The Cell Monitors are placed on the batteries and wired back to the WatchMon-CORE supervisor via an IsoMon. 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

CellMate-K9 is lower in cost (~50%) and has fewer parts, therefore it has fewer things to go wrong. The wiring is easier as it uses the shared loom, adopted by many of the prebuilt in OEM batteries or you can create your own. We always recommend that you fuse your cells close to the battery to protect this wiring. There are fuses and holders available for this purpose.

Confirmation of Wiring Success

CellMate-K9 can verify that the wiring is correct before connecting your battery to the module by using a TestMon, making it easy to use and simple to install. The TestMon was needed for WM5, WM7 and MM8, however, with CellMate-K9 as this is much more intuitive monitoring, you can just adopt a multi-meter and verify the plug prior to connecting to the cell monitoring unit (CMU).

Both the central and decentralised monitor can use the Network Test to confirm that the CMU communication cabling is done correctly. If the software of the Network test does not pass, you will need to check the wiring of each wire until you find your problem, you cannot proceed until you get a pass.

What Batteries are Able to be Monitored by Each CellMon

Central (CellMate-K9) is more flexible as it can deal with Shared Loom batteries, such as Tesla, Nissan Leaf, Chevy and Fiat and also extends the voltage range allowing LTO batteries to be monitored.

( Note: LTO due to the lower voltage per cell of 2.4v has its own variant that you can ask for)

The CellMate-K9 can also be wired up to all the other batteries that decentralised BMS is capable of monitoring.

Decentralised cell monitors require a cell monitor per cell in series, LeafMon for use with Leaf cells, BlockMons for use with Prismatic cells and LongMons for others.

(Note: Individual cell monitors are not suited to OEM shared loom batteries).

Temperature

CellMate-K9 has 4 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.

Compatibility

Anything compatible with WatchMon4 is compatible with the WatchMon Series.

Balancing Power

Individual cell monitors are able to balance 28.8Ah per cell per day, with a maximum of ~2A, but a typical achievable power of 0.8A.

Central (CellMate-K9) is able to balance 6Ah per cell per day, with a max of 0.9A but a typically achievable power of 0.7A due to the design with a heatsink and fan.

Typically, the daily balancing requirement for a battery cell 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. Please note that because decentral balancing is higher than CellMate-K9 it does NOT make it more powerful. This is not based on POWER it is based on BALANCING.

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 Decentral (LongMon/BlockMon)?

If configuration outside of the typical 7-16s groupings (for example 4 multi-strings of 4S1P i.e. 4M4S1P)
Have existing cell monitors that you wish to reuse
Ideally suited to large format prismatic cells
If any cell goes below 2V all visibility of the pack is lost until all cells are above 2v
Not generally recommended for new projects

Why would I choose a Central (CellMate-K9)?

Suitable for OEM batteries such as Tesla, Nissan Leaf, Fiat, Chevy Volt etc
Suitable LTO batteries, therefore, allowing wider voltage range
Able to be used for most popular Lithium cells
can be used in multi-string parallel or higher voltages in series by using multiple.
Simpler and easier installation
less complicated wiring and no tiny connectors
Able to monitor the entire pack even when a cell goes below 2V or all cells for that module go flat.
Bypass heat can be achieved away from the battery cells to prevent these from heating up when balancing.
Better value with the same functionality as individual / distributed
All in one solution with fewer things to go wrong.