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RS-485 DB9 Connector Pin Assignments

I would like to connect a PC to the Active BMS using a USB-to-RS485 adaptor.  As a first step I examined the pin assignments for the DB9 connector.  These are shown on Table 5 in the user manual.

The pin assignments in the manual look like a half duplex RS-485 connection with one exception.  There's an extra pin labeled "+5V to AGND".

Rick: Could you please find out the function of that pin?

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Hey Rich, I am guessing that might be to power the RS485 to USB in the custom programming circuitry but you would need to contact REC directly to confirm.  On that note your programming software includes a PC to REC cable that should allow you to use that.  There are also a couple of folks on githb that have built CLI interfaces, one using PowerShell and the other using JS.  I have not had a chance to test either but they are open source and may hep with your project.

Also, I have tested several Chinese USB-RS485 cables trying to find a cheaper alternative, but have not had any luck to date.  Let me know if you find anything.



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Has anyone found an alternative RS485 to USB cable/adapter for the REC-BMS?  I was hoping to buy a generic one instead of paying $70 for the REC product.