Dynamic Product Search

Smart Energy Management for Marine and Off Grid


No products in the cart.

REC and WS500 User Forum

Please or Register to create posts and topics.

Cutting BMS Wires


I am starting to build my diy battery drop in box. It is designed to drop into a 8D fiberglass battery compartment. I assume it’s ok to cut most wires to make the build a bit cleaner. I will not cut the cell wires, but others should be ok to cut? Wires like the shunt sense wires, Bluetooth power wires, signal and relay wires from the BMS harness? If all goes well, I will build 3 more.

Uploaded files:
  • 2C515404-E16D-48F6-AE05-2082F96F0192.jpeg
  • BA19D539-A581-4EE5-9518-93F47EE0226E.jpeg
  • A6F86B1A-7B6D-4BAE-B3D2-647384A1F4C2.jpeg

It looks like you have a good start on your project.  Nice one.

Yes, you can cut the wires, but NEVER while the BMS and cells are connected, as this will damage the BMS.

Try to keep all of your cell monitor wires the same length.  Everything else is flexible.

And remember that for parallel systems, your main power wires should always be equal length from pack to the main bus bar.  This will help keep your packs in balance.


Thanks Rick,

Unfortunately because of the physical locations of the batteries on the boat, my charge/discharge cables are at different lengths. No way around that. They are 4/0 cables, which will minimize the effect ( IxR losses)  of the different cable runs.

Here is the schematic of my battery boxes. If you see something you are concerned about, please discuss. I may remove a number of wires that I don’t use from the BMS connector. I will also shorten all other wires as needed except the communication cables (Can Bus and RS-485) and the  cell monitor cables. I and also adding a Y connector to the RS-485 to be able to operate the Bluetooth module as well as be able to plug in a pc if I want to tweak the parameters. The best performance of the Bluetooth occurs when it only talks with one or the other but not both at the same time. The battery boxes are physically located under beds and saloon seating on the boat, hence the remote panel.


Uploaded files:
  • FD670491-E4AC-44F0-8D88-561BFF7F1DB6.jpeg

Nothing is jumping out at me here Patrick.  My reference to battery pack cable lengths only applies if you have multiple groups of cells, like in a 2P4S 2P configuration.  Because you only have a single set of cells there is no issue there.

Best of luck with your install, it looks like you have it well in hand!