MODBus Communication to JBD BMS

[dhruv_pareek]

Hello, I am trying to use a microcontroller (specifically an Espressif ESP32 with an RS485 MAX module) to communicate over MODBus to my JBD BMS (model name: JBD-AP21S001) but I am having issues getting this to work.

I understand that there is an RS485 Communication Module that JBD sells with the BMS (https://www.aliexpress.com/i/3256804168676247.html?gatewayAdapt=4itemAdapt#nav-specification). Is MODBus communication to the BMS only possible by purchasing this module? Or is this module only necessary if you desire to communicate with the BMS through your laptop?

The RS485 port on the JBD BMS only has two pins built in for A and B, just connecting my RS485 MAX module to the two A and B pins of the RS485 port of the BMS does not work properly. I also tried to solder on wires to what looks like a ground and BAT+ label of the RS485 port, then connect these wires to the GND and 5V of the ESP32, however this does not work properly either.

So do I need the RS485 Communication Module that JBD sells with the BMS (https://www.aliexpress.com/i/3256804168676247.html?gatewayAdapt=4itemAdapt#nav-specification) to communicate over MODBus from my ESP32 with an RS485 Max module?

 

[Luk88]

I'm not sure about JBD. With JK they don't use modbus.They use their own built in protocol that is well documented. They have a so called GPS port which I heard makes TTL (3.3V!) UART available using that protocol. And Bluetooth of course.

Perhaps this is similar?

 

[shvm]

You can use BLE directly or if you want to go wired, you need to Unplug the BT adapter already connected to the port.
Either ways, the communication goes through the UART port.

Instructions and files here.

GitHub - syssi/esphome-jbd-bms: ESPHome component to monitor and control a Xiaoxiang Battery Management System (JBD-BMS) via UART-TTL or BLE

ESPHome component to monitor and control a Xiaoxiang Battery Management System (JBD-BMS) via UART-TTL or BLE - syssi/esphome-jbd-bms

github.com

 

[Pierre]

Some of the newer JBD’s can be ordered with both UART (for BT dongle) and RS485 ports. I imagine you would require their proprietary interface module for the RS485 coms.
https://www.era-energytech.com/product/jbd-rs485-to-usb-converter/ .

 

[ThaiTaffy]

Hello, I am trying to use a microcontroller (specifically an Espressif ESP32 with an RS485 MAX module) to communicate over MODBus to my JBD BMS (model name: JBD-AP21S001) but I am having issues getting this to work.

I understand that there is an RS485 Communication Module that JBD sells with the BMS (https://www.aliexpress.com/i/3256804168676247.html?gatewayAdapt=4itemAdapt#nav-specification). Is MODBus communication to the BMS only possible by purchasing this module? Or is this module only necessary if you desire to communicate with the BMS through your laptop?

The RS485 port on the JBD BMS only has two pins built in for A and B, just connecting my RS485 MAX module to the two A and B pins of the RS485 port of the BMS does not work properly. I also tried to solder on wires to what looks like a ground and BAT+ label of the RS485 port, then connect these wires to the GND and 5V of the ESP32, however this does not work properly either.

So do I need the RS485 Communication Module that JBD sells with the BMS (https://www.aliexpress.com/i/3256804168676247.html?gatewayAdapt=4itemAdapt#nav-specification) to communicate over MODBus from my ESP32 with an RS485 Max module?

The max will require a gnd from the BMS you can't connect to the esp gnd (I've learnt the hard way and cooked a few max chips in the past) also make sure the Rx from the Max goes to tx on the esp and vise versa for the other wire. Set up UART debug in your code verbose logging and check what data your getting.

 

[chilly2]

On that note, and this is probably a long shot, but I think my rackmount battery has a JBD BMS inside it. No idea what version, but it uses Bluetooth. Is it possible to switch out the BT for RS485 if I crack the case open, or can SolarAssistant talk over BT to the BMS maybe.

 

[Pierre]

Removed.

 

[Pierre]

On that note, and this is probably a long shot, but I think my rackmount battery has a JBD BMS inside it. No idea what version, but it uses Bluetooth. Is it possible to switch out the BT for RS485 if I crack the case open, or can SolarAssistant talk over BT to the BMS maybe.

I think you need this :

JBD UART to USB Converter - ERA Energy Tech

This JBD tool converts the UART signal from the JBD BMS board to USB format to facilitate programming of the JBD BMS on your PC. Please note: Only this tool or the Bluetooth dongle can be connected to the BMS at any one time.

www.era-energytech.com

 

[ThaiTaffy]

I think you need this :

JBD UART to USB Converter - ERA Energy Tech

This JBD tool converts the UART signal from the JBD BMS board to USB format to facilitate programming of the JBD BMS on your PC. Please note: Only this tool or the Bluetooth dongle can be connected to the BMS at any one time.

www.era-energytech.com

The esp will do the same job, likely either he has a gnd missing from the data line or the UART data lines crossed.

 

[dhruv_pareek]

By "UART data lines crossed" do you mean that my A wire and B wire are crossed when connecting the RS485 port on the BMS to my RS485 MAX module?

Also, do you think connecting the RS485 port of the BMS to this RS485 to usb converter would work? I would like to connect this USB converter to the BMS so that I can use a MODBus simulator software on my computer to communicate with the BMS before I use the ESP32.

Edit: Got this to work using the RS485 to USB converter! I think my issue was with the ground wire. Going to try to make it work with the ESP32 next!