Need help with RS485 JKBMS and Gootu Inverter

[solar_4_life]

Hi, I am trying to get my jkbms pb1A16s15a to speak to my inverter (gootu 8.2kw hybrid) using rs485 communication (pylontech low voltage 3.5 9600 baud rate) . Both my inverter and bms support the protocol .
However when I connect the cat6 cable the connection doesn't establish. I did look at the connection diagram given by both the inverter as well as the BMS :


This is the image from my BMS manual. The connection diagram from the inverter is as below :

I am not able to figure out how to do this connection. Please help .

 

[kommando]

You need to split the cable and join up different wires so you get

JK end 1=B 2=A 3=GND

Inverter end 1=B 7=A 2=GND

 

[solar_4_life]

You need to split the cable and join up different wires so you get

JK end 1=B 2=A 3=GND

Inverter end 1=B 7=A 2=GND

Hi, thanks I tried as under


Left side is inverter. 1,7 and 2 go into 1.2 and 3 on the JKBMS . Unfortunately no luck .

 

[kommando]

Try swapping A and B, there are different interpretations. Also check the baud rate is same on BMS and inverter.

 

[solar_4_life]

I got another drawing from the inverter manufacturer

Now I'm connecting wires as
Orange/white to BMS brown /white
Orange to BMS brown
Brown to BMS green

Still no luck. The default baudrate for both inverter and BMS is 115,200. Do I need to check it? Thanks

 

[kommando]

The baud rate on the JK is fixed by setting the protocol, so check the inverter to see if it set correctly. Also check the voltage between A and B for the JK and the inverter separately ie with the middle of your split cable not connected.

 

[Luk88]

Please note the messed up rj45 pin numbering on all pictures except the inverter manual. The second picture you got from the inverter manufacturer uses misleading graphics. Let me explain why.

PIN numbers on this picture:

Are very similar to my Y&h inverter. Specifically the rs232 port is exactly the same if you ignore the picture and use this numbering:
(disregard colors, pin numbers is what matters)

So to repeat. My rs232 port pin numbers are exactly as on the black/white picture if you use the numbering on the color picture above.

Same for RS-485 pins A and B. Specifically pin 1 is A, pin 2 is B.

To get it to work you have to connect RS485A to A on the other device and B to B on the other device. That's it. But you need to figure out the pin numbers.

So if it was only a matter of whether the pin numbers are reversed or not on the inverter it would be pretty simple. You could try pin 1 - A, 2 - B, or if reversed pin 8-A, 7-B. But that other picture from the inverter manual blows that idea up by saying pin 1 and 3 is B and 7 is A. You can exclude that scenario pretty quickly by testing continuity between pin 1 and 3. If these two are not connected this picture can be disregarded.

Then we have the BMS. Looking at the manual it seems it covers both scenarios, but A and B is reversed
So in the BMS it seems we have pin 1 and 8 is B, pin 2 and 7 is A.

So in the first instance (assuming pin 1 and 3 on inverter side have no continuity) I'd try if a normal Ethernet cable (straight) works. It might.

If it doesn't cut that cable and swap pins 1-2. If your cable uses colors like in my color picture you would swap solid orange with orange-white. Check if this works.

If it doesn't... It requires more involved testing.

 

[solar_4_life]

Thanks for the suggestions.

I tried straight cable and pin 1&2 into 7&8 in the BMS - both permutations and nothing worked .

Checked the voltage on a dmm. Inverter pin 1& 8 shows 1.05 . 2&8 shows 1.06 . Pin 4&8 has 5.05 (this is as shown in the figure)




The BMS pins have voltages as
1/8 &6 2.16
2/7 &7 2.17

The voltage between A&B on the inverter fluctuates between 0.1 to 0.4

The voltage between A&B on the BMS is 0.00

Does it meant that BMS has no rs485 signal?

I'm stuck now .Don't know how to test further.