ESP8266 does not have bluetooth, it is wifi only. So if you want to use this chip you will have to hardwire the uart pins on the esp8266 to the jk bms and it will work just fine. If you prefer to pull the data from the jk bms wirelessly you can do that over bluetooth with an esp32 chip which has both bluetooth and wifi.How about these guys ? ESP8266 I have been playing with them.
As I understand it, they work with the same code, just have to program as an ESP8266 not ESP32.
We don't need many pins for the simple serial data we are looking at.
The esp chips pull the data from the jk bms (either over bluetooth or serial), and then they relay that data back to home assistant over wifi. You can control all the settings thru home assistant just the same as you can over the JK phone app.
GitHub - syssi/esphome-jk-bms: ESPHome component to monitor and control a Jikong Battery Management System (JK-BMS) via UART-TTL or BLE
ESPHome component to monitor and control a Jikong Battery Management System (JK-BMS) via UART-TTL or BLE - syssi/esphome-jk-bms