20s BMS green bike kit wiring - questions

Hi all,

I purchased a 20S BMS 100A from greenbike kit. This BMS will go with a 20S14p battery. it is the first time I am building a battery so forgive me for the questions if they are dumb.


This is the diagram I have from the company:


connect 3 wires from B- to the negative port of the battery. I checked with an ohmmeter and the 3 B- port are connected on the circuit board. They have the same potential. Can I connect only one wire from B- to the cathode (second drawing) of the battery or should I really connect 3 of them to the battery? I guess because of the 100A limit I need 3 of them.


From the anode of the battery I will have to connect the + of the XT60 cable (charger) and the + of the XT90 cable (controller). Then I will have to connect the – of the XT60 cable and the – of the XT90 cable to the 3 different ports C- , not to only one port.
There is a P port but it is not in used here.

Thanks for your answers.

Best regards,

Peterfr

How thick of a wire are you using? Is it multi strand of solid core? How thick are the traces on your BMS PC board? How long are the wires going to be? All these kind of questions come up in a high-current situation.

If you look at AWG current charts you will get some idea of what kind of a wire thickness you will need. If it seems like you will need thick wire, you are right. However, the wire can probably take more current then advertised, but how much more is a guess.

If you are going to use big amps, you will need fat wires. You should also keep the length of the wires as short as possible. I would wire it as the manufacture stated to distribute the load as intended. Or, you just might turn your one wire, and your BMS traces into something like the red glowing wires in a toaster oven.

Hi e-beach

Thanks a lot for your comments.
I am going to use 10AWG Silicone Stranded 1050/0.08mm Wire RC.

Technical Information about the wires I purchased:
Overall Diameter
5.4mm
Stranding
1050/0.08mm
Voltage Rating
600V Maximum
Temperature Range
-60°C to +200°C
I will check tonight the trace on the BMS circuit but they do not look so thick and will keep them as short as I can.

I will spread the load with the 3 different wires. i am not planning to use 100A, maybe 70A maximum when going uphill.

Best regards,
Peterfr

Be sure to keep the wire lengths to a minimum, and remember that the more strands you have the less amps the wire can take. Solid core wire can take more amps, it is just harder to work with and not flexible. Try it with the silicone wire but check for heat when you start using it. If it is gets hot with silicone wire, reconsider your options.