How to interface is it RS232 or RS485 if I want to use a wired connection to my BMS using an ESP32

[Mvanmierlo]

I am a bit puzzled by how I can interface my JK_PB2A16S20 V15 BMS to my ESP32.
I prefer a wired connection as my batteries are in a metal closed so range of Bluetooth is none existing when the doors are closed (normal operation).

I found on the main page a refer to interfacing using RS232 via a UART port, and although I have the standard communication board with the RJ11 connector wired to the P2 connector RX / TX / GND on the BMS, I am not able to get any information out of this port (I tried really hard with all kinds of way of connecting it, but No output is comming out of that port)

Than I see a modbus example but there's no clear documentation how to wire my ESP. JK BMS documentation is talking about RS-485A and RS-485B connections but all the example I see here are mentioning RX / TX.

I associate RX/ TX with a serial RS232 connection, not RS-485. But maybe this got lost in translation somewhere ?

If I am able to connect my ESP direct on the RS-485 port great but I would be more than happy if someone can explain this to me to add some documentation on the front page of this GitHub to clarify this a little.

So can someone confirm that if I use RS485 -1 I can use the Modbus example and just connect RS485A-1 and RS485B-1 to my ESP (do I need GND normaly RS485 is not perse using GND as far as my experience goes).

Thanks for your help.

[syssi]

So can someone confirm that if I use RS485 -1 I can use the Modbus example and just connect RS485A-1 and RS485B-1 to my ESP (do I need GND normaly RS485 is not perse using GND as far as my experience goes).

A RS485 converter is required between the ESP32 and BMS. I can recommend this module:

https://github.com/syssi/esphome-jnge-mppt-controller/blob/main/images/circuit.jpg

The UART interface of your ESP is a UART-TTL interface. The voltage level of UART-TTL is 0/3.3V. RS485 uses differential signaling. A converter is required. You can find some important details here: https://github.com/phinix-org/Multiple-JK-BMS-by-Modbus-RS485?tab=readme-ov-file#multiple-bms-and-parallel-powerbanks

Some steps to speed things up:

1. A ESP32 is recommended
2. Attach the RS485 to your ESP. Don't use the RXD/TXD pins because they are used by the logger component already.
3. Attach the used GPIOs to the uart component at the YAML configuration
4. Use the left RS485 port called RS845-1 and set the device_addr to 0
5. Attach PIN1 of the RJ45 jack to A+ of the converter, PIN2 to B-, PIN3 to GND

That's it!

[Mvanmierlo]

Thanks for your quick help !
That clarifies a lot where could I have found this in the documentation (aka did I search enough ? )

Still more a fan of the RS232 connection (not needing a converter) so wondering if anyone got this working with a connection via the RJ11 / RS232 port on the JK Communication board.

[syssi]

There is not much known about the RS232 port & communication protocol here. See #408

[syssi]

You could try to capture the RS232 traffic between the BMS and the Windows application.

[Mvanmierlo]

I manage my JK BMS with my RS485 to USB converter, as far as I know there is now RS232 option available.
Will check if I can probe the RJ11 port with a logic analyzer to see if anything happens here, I did a check and the port is connected to the BMP port P2 on pins 3 4 and 5.
But like you mentioned not much known, and probably not implemented in the JK Firmwares.

So guess my options are limited to BLE or RS485 and I will order a few converter boards like you mentioned to try the RS485 option.

But if I may speak freely I am still a bit puzzled by the info provided on the main page of this Git, as from the little info I get from it at the schematics section in regard to interfacing this is still direct RS232 from the BMS (the TTL UART port) based on RS232.
But I have no such option on my V15 BMS. So maybe this can be updated to make this more clear (I am happy to help if you do not have the time).

[syssi]

Thank you for the detailed feedback and your willingness to help! You're absolutely right about the documentation needing clarification. I should have been more specific about the hardware differences between BMS generations.

The truth is, I only have access to older BMS models, which makes it easy for me to provide reliable support for Bluetooth, the GPS port, and the display port on those devices. However, I don't have access to the newer V15 and V19 models, which is why I struggle to provide accurate and reliable information for these versions. Your experience with the V15 is exactly the kind of real-world information that would help make the documentation more accurate and useful for other users.
I would very much welcome your help in updating the documentation to better reflect the differences between the older models (with direct TTL UART/RS232 options) and the newer V15/V19 models (with their different interface options). If you're willing to contribute your findings - it would be greatly appreciated!

Support and contributions from users like you who have hands-on experience with the newer models are always welcome and make the project better for everyone.

[Mvanmierlo]

I have both V15 and V19 BMS's so I can help you with that no problem and already started with documenting my findings with the V19 board (as this is in my latest battery box and not yet in production as I am still waiting for my cells to arrive).

[ircoopr]

I think I'm about to embark on the same quest, though hopefully with multiple slave bus. How are you getting on with documentation? I'm happy to contribute

[konstal2004]

Can I use the module https://lilygo.cc/products/t-can485 to read data from the RS485?
Which .yaml file should I use for this?
And the second question: if there are multiple storage devices connected together, will I be able to read all the data from the master? How many storage devices can the ESP32 handle?

[syssi]

Yes. It's possible if you use the left RS485 and talk to the BMS using the slave address selected by the DIP switches.

[konstal2004]

This is great information. Could you show me what I should change in the esphome code to add a second energy storage?

[syssi]

Are you able to talk to a single device?

[konstal2004]

Not yet, I'm waiting for the ESP32 with RS485. I'm wondering what I should change in the code to read data from multiple battery.

[syssi]

Please lets start with a single BMS and let's move on as soon this is working. :-)