Connecting Cell Monitors to OEM Batteries With a Shared Balancing Wires Harness

If you are considering OEM packs like Tesla, Nissan Leaf, Chevy Volt, etc. it is very important to plan in advance how the balancing wires will be connected to the cell monitors. 

Basically, if you have the Watchmon4 with multiple cell monitors like the LongMon, the short answer is: avoid using their original balancing harness and wire the cell monitor red/black wires directly to the cells.  

The original OEM balancing wires are usually long and thin designed for much lower balancing power, around 300mA. Our cell monitors are balancing at 2.2A peak or 1.2A continuously each which is at least 4x times higher balancing power.

This means that if two cell monitors are sharing the same wire, it is effectively 4.4A. When both adjacents cell monitors are bypassing (balancing) through a wire that was designed for 300mA, this will cause a significant voltage drop and the cell monitor will not operate properly. 

Shared balancing wires will also cause interference during the cell balancing when neighbor Cell Monitors are trying to both balance and read through the same wire, at the same time. This will cause voltage drop and misreadings.

Wire positive (red) and negative (black) wires directly to each cell terminal and it will work like any other non-OEM battery.

WatchMon5 (coming soon) all-in-one solution, suitable for OEM batteries.

​We are working on an easier solution for these OEM packs (Tesla, Nissan Leaf, Chevy Volt, etc). This all-in-one solution will make wiring much simpler. This system is a lower power version limited to 300mA, following all other OEM automotive battery management systems in the market.

This permits the use of the existing OEM "shared" balancing wires that can only take 300mA, without the need to open the pack plastic/metal case to access the cell terminals. Two big screw-terminals (yellow connectors) will make wiring much faster.

Keep your eyes on our website for the latest product updates.

WatchMon5 should be available in a few months time.