Jikong JK BMS

JK (Jikong) BMS support

This project supports communication with a JK BMS using a wired medium. Parameters are polled at customizable intervals and displayed in the Web UI as well as published to the MQTT broker. The main benefit is usage of the battery State of Charge (SoC) value to control the Dynamic Power Limiter.

Supported Devices

This feature was tested against a JK-B1A24S15P model. It is assumed that all JK BMS implement the same protocol on their UART interface. The following models are listed in a manual that includes the tested model:

JK-BD6AxxS-6P  / JK-BD6AxxS-8P
JK-BD6AxxS-10P / JK-BD6AxxS-15P
JK-BD6AxxS-20P / JK-B1AxxS-15P
JK-B2AxxS-15P  / JK-B2AxxS-20P

Notice that buying the BMS with the CAN interface or the GPS feature might conflict with the UART interface.

RS485-TTL (UART) Jack

This is the pinout of the communication jack on a JK BMS (4 Pin, JST SH 1.25mm pitch):

┌────  ─────  ────┐
│                 │
│  O   O   O   O  │
│ GND  RX  TX VBAT│
└─────────────────┘
   │   │   │   └── VBAT is full battery voltage, e.g., 51.2V (do not connect)
   │   │   └────── ESP32 GPIO (RX pin)
   │   └────────── ESP32 GPIO (TX pin)
   └────────────── GND

This is the underside of a JK-B1A24S15PH and the respective port is connected with an RS485 converter (JK accessory):

The orientation of the pin-out above matches this style of JK BMS. NOTICE that on these black JK BMS this port is soldered on the PCB's bottom side. On other JK BMS, e.g., the ones with a bare aluminum chassis, the connector is soldered on the top side, so the pin-out is to be read upside-down!

Wiring

Multiple wiring methods are supported. The battery.rx and battery.tx pins must be defined in the pin mapping for all methods. When using the RS-485 Transceiver on MCU interface type, battery.rxen and battery.txen pins must also be defined. See the device profile documentation for more details.

UART-TTL

The BMS may be connected directly to two ESP32 pins. For the UART receive pin on the ESP32 an input-only pin may be used.

NOTE: Do NOT connect the fourth pin (VBAT) of the JK BMS, as it drives the unregulated full battery voltage.

Use this setup only over short distances as it is not robust against interference.

          UART-TTL
┌────────┐         ┌───────┐
│        │<TX---RX>│       │
│ JK-BMS │<RX---TX>│ ESP32 │
│        │<--GND-->│       │
│        │   3V3-->│       │
└────────┘         └───────┘

Use the TTL-UART on MCU interface type in the OpenDTU-OnBattery settings for this setup.

Untested: RS485 with Transceiver and UART-TTL

Using the original JK BMS RS485 adapter, the wiring can be completed using an RS485 to UART-TTL converter board. Search for DEBO TTL-RS485 on reichelt.de for an example. For the UART receive pin on the ESP32 an input-only pin may be used.

This setup also works over long distances for the RS485 lines.

           UART-TTL              RS485           RS485-TTL
┌────────┐         ┌───────────┐       ┌────────┐         ┌───────┐
│        │<--TX--->│Y    JK   Y│<A---A>│        │<TX---RX>│       │
│ JK-BMS │<--RX--->│W  RS485  W│<B---B>│ RS485  │<RX---TX>│ ESP32 │
│        │<--GND-->│B Adaptor B│<-GND->│ to 3V3 │<--GND-->│       │
│        │<-Bat V->│R          │       │        │<--3V3-->│       │
└────────┘         └───────────┘       └────────┘         └───────┘

Use the TTL-UART on MCU interface type in the OpenDTU-OnBattery settings for this setup. The ESP32 will talk UART to the converter board. The RS485 transceiver is transparent to the ESP32. That also means it has no explicit control over the transmitter or receiver. That in turn might cause the ESP32 to read its own data. If that's the case, you will see errors in the message output (web console, serial interface), but the communication should still work. This is still to be tested.

RS485 with Transceiver only

Using the original JK BMS RS485 adapter, the wiring can be completed using only an RS485 transceiver chip that is connected to the ESP32 directly. This is the case for the OpenDTU-FUSION board, where an ISL3178E transceiver is in use. There are also breakout-boards available that only have a RS485 transceiver (search for MAX485 Module).

This setup requires four pins on the ESP32: Two for data (one input, one output), one that controls the receiver, and another that controls the transmitter. The latter two are outputs.

          RS485-TTL               RS485
                                    ┌──────────────────────────────┐
┌────────┐         ┌───────────┐    │    ┌───────────┐   ┌───────┐ │
│        │<--TX--->│Y    JK   Y│<A--+--A>│A      RXEN│<->│15     │ │
│ JK-BMS │<--RX--->│W  RS485  W│<B--+--B>│B        RX│<->│16 ESP │ │
│        │<--GND-->│B Adaptor  │    │    │       TXEN│<->│46  32 │ │
│        │<-Bat V->│R         B│<-->│GND │ISL3178E EN│<->│45     │ │
└────────┘         └───────────┘    │    └───────────┘   └───────┘ │
                                    │       OpenDTU Fusion v2      │
                                    └──────────────────────────────┘

Use the RS485-Transceiver on MCU interface type in the OpenDTU-OnBattery settings for this setup.