JK (JiKong) RS485 interface wiring


New Member
Dec 14, 2021
My JK RS485 got chineese letters to identify colors for A and B.

Looks like JK made two different covers for the RS485 interface

I used Google Translate to identify the colors.

Since the result from Google is the same as the english version of the interface I will use this.

Hope this could be useful for others.


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Saturday morning in rainy northern Europe;
I was going to do some testing;

On the table I got my 200 amp
JK (JiKong) B2A8S20P BMS

I was going to hook up my RS485 interface.

The interface comes with a 4 pin plug,
This BMS port labeled RS485 is a 3 pin port,

Next to the RS485 port there is a 4 pin port labeled GPS,

The datasheet give a lot of info;
Also the following text;

GPS (optional) Support (GPS or 485 just choose one)

Other interfaces (customized) RS485/CAN

I also got a interface that suppose to be a CAN interface. This interface also got a 4 pin plug.

My question; Would the 4 pin port labeled GPS also be the port for my 4 pin RS485 interface?

Why sell a bms with a 3 pin RS485 port, and interfaces with 4 pin plugs….. Just to confuse me ?


Yeah… maybe I need to ask the seller in China ?


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It's just UART/TTL - so you don't need the adapter, just a TTL/USB adapter will do. Pinout is on my Github here in the readme:

That's great that it's available straight from the terminal. I'm looking at getting JK-B2A8S20P but definitely need RS485. I assume it doesn't come with a cable to connect to the RS485 terminal?

Would you mind letting me know when type of connector it is please?
Thank you. I just received the new JKBMS B2A24S15P, can I use your mount with ESP32 and TJA1050 to connect it to my Growatt SPF5000ES?

You don't need that. All you need for communications is RX, TX and GND.

Does that mean I could connect those to a serial cable? I was not able to get my RS485 -> USB working with a PC, this would be simpler (as well the fact it might actually work) as I have a few old serial cables lying about in boxes of PC stuff.


If your serial is true RS-232, then not directly and you need a TTL to RS-232 converter. Easiest is just to get a TTL/USB converter and re-purpose the cable from the RS485 dongle.

If your serial is true RS-232, then not directly and you need a TTL to RS-232 converter. Easiest is just to get a TTL/USB converter and re-purpose the cable from the RS485 dongle.

Sadly my last PC with a serial port died recently. So all I have are a few unused Serial to USB cables (various chips), don't know if they are suitable. I do have serial cables which I can cut one end off, and put some pin sockets on the end of.

I bought an RS485 with each JK BMS, and an RS485 to USB, but it never worked. Actually, the first one didn't work, the second one I attached to the first JK, and it didn't work either. But, I don't know if it's the first JK at fault or not. I can't easily access the 2nd BMS due to space constraints. I'll try to put it on there one day.

At the moment I'm using a pair of Android phones to display the JK apks on a PC. Eventually I'd like to use the PC direct to the BMSs.