Juntek DC KG140F and HK140F are Coulometers. They use a shunt to measure DC current. There are several brands on Amazon and Aliexpress.
According to the Manual:
JUNCTEK is a registered trademark of Hangzhou Junce Instruments Co., Ltd.
- KG-F KH-F Series Coulometer or other hardware that conforms to the same output format as described in the Juntek (or Junctek) KG Manual KH Manual.
- RS-485 to USB or Serial Adaptor.
- An attached screen to KG-F. This is technically optional. The screen automatically sends a command to the Coulometer to trigger a statistics response. The script simply reads the results. The script could also be modified to send the command itself if needed.
- Python 3
- systemd-watchdog (if run using systemd daemon). Install by
pip3 install systemd-watchdog. - MQTT Broker
- Home Assistant MQTT Integration (Or any other MQTT consumers)
This script reads from a serial port and decode the plaintext output from the Juntek device. Edit the following variables in the python script:
- ser: Point to your actual serial port
- tag: Name the Entity prefix you would like the MQTT topic to use.
- totalAh: Assuming you are using the Coulometer to monitor a battery or battery bank, provide the total Ah capacity of the battery for calculating State of Charge (SoC).
Search for the line publish.multiple and customize for your MQTT broker.
For testing purposes, change the mode variable to "screen" and it'll print the output to stdout instead of MQTT.
Formats are described in the manual. Here is an example:
b':r50=1,34,5166,1030,109337,11738441,62100651,48663,125,0,99,0,644,9117,\r\n'
Description Example
b':r50=2,215,2056,200, 5408,4592,9437,14353,134,4112,0,0,162,30682,\r\n'
2 represents the communicationaddress;
215 represents the checksum;
2056 represents the voltage of 20.56V;
200 represents current 2.00A;
5408 represents the remaining battery capacity is 5.408Ah;
4593 means the cumulative capacity is 4.593Ah;
9437 represents the watt-hour is 0.09437kw.h;
14353 represents the running time of 14353s;
134 represents the ambient temperature is 34℃;
4112 represents the power of 41.12W;
0 means the output status is ON;
(0-ON, 1-OVP, 2-OCP, 3-LVP, 4-NCP,5-OPP, 6-OTP, 255-OFF)
0 represents the direction of current, and the current is forward current;
(0-forward, 1-reverse)
162 means battery life is 162minutes;
30682 represents the internal resistance of the battery is 306.82mΩ.
Some code structures especially the MQTT formating are inspired by the mpp-solar project