First, a big thank you to tgalarneau for creating his bms project, which I used as a base to build this code. tgalarneau's bms project is a more general purpose project that uses socket or mqtt connections. I needed a streamlined mqtt based code set that simply published a single mqtt message to a broker, which I will process into a MariaDB database and then display using Grafana. And I only need to process 4 cell (12v) batteries.
His project is more sophisticated by far, and you should check it out.
I've added several features to the python code.
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You can pass a BLE device name or address. If an address is passed the code simply uses it. If a name is passed the code will scan all localbluetooth devices to find a matching name, extract its address, and use it.
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The code will query basic BMS data and cell voltage data, and then combine that data into a single mqtt messsage.
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The processing interval is changed to use minutes rather than seconds, and there is now an
option to use a "one and done" process by passing in a zero (0) for the interval option. -
The code has more comments explaining things, and was restructured for more clarity.
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This code runs fine on the latest Rasperry Pi OS (Bullseye) and is being used on 3b+ and 4b models (1gb 3b+ and 8gb 4b). You will need Python3 installed. You will need bluepy installed. And you will need the paho MQTT package installed. And of course you will need a MQTT broker set up to send the messages to. Other than that, it's straight forward..
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The code should be run as SUDO as it does low level BLE scanning.
Run it as follows:
sudo python jbd-bms-mqtt.py -n "Cabin 580ah" -i 0 -t solar or sudo python jbd-bms-mqtt.py -a "a4:c1:38:30:c2:8e" -i 0 -t solar
This will scan for a bluetooth device called "Cabin 580ah" and extract its bluetooth address, or, use the passed address if provided, then try and attach to the BMS and read a set if variables, one time, and then publish a MQTT message with those variables to the Topic "solar".
USAGE NOTE If you use a value other than 0 for the -i parm the program will loop forever and read the BMS values every X minutes based on the value you passed. This is not recommended as a long term method to run the script, as it could cause resource issues in the python environment. For an ongoing run please use a cron job to control run times and pass a 0 for the -i argument...
In addition, if you run this program via a manual shell loop instead of using cron, and someone attached to the BMS using a bluetooth app (like XiaoxiangBMS or SmartBMSUtility) the code will fail when it attempts to connect (as the other app has the connection) and will throw an exception. If you started it intending it to run "forever" in a terminal window you will not realize it's failed.
If cron is used, at least the process will be kicked off again based on the cron process and try to reconnect again, automatically...
You've been warned!
Note: There are two versions of the code, one for a 2 Tempurature BMS and one for a 3 Tempurature BMS. For my purposes I only write 2 sensor values to my database so I simply don't include the third sensor in my MQTT message in the 3 Temp version. If you want all 3 tempuratures just add the additonal statements in the MQTT build message section at the end of the code...I need consistancey between the 6 BMS' I run (some with 2 and some with 3).