BMS-Software

Python 3 Software for the Battery Management System with Active Cell Balancing

Python Script

The main python 3 script theBMS.py uses three classes as described below.

This main script is designed to run on a RPi Zero W and implements pushing to a MySQL databse as a proof of concept.

If this feature is not needed, comment out line 95 and line 96 in the file theBMS.py, otherwise modify the credentials / query.

Classes

The classes BMS, SunnyBoy and isoSPI are used.

BMS

The BMS class models the whole battery management system (number of boards, voltages, ...).

SunnyBoy

The SunnyBoy class models the fictional communication to a battery inverter called "Sunny Boy Storage 2.5".

isoSPI

The isoSPI class handles the isolated SPI communication with the IC LTC6813-1. This is done by using a C++ program (see Communication). Furthermore the class is responsible for calculating and checking the package error code (PEC).

Communication

Due to timing contrains, the actual isoSPI communication was implemented with a C++ program.

Usage

This program must be run with superuser privileges.

Usage: ./isoSPI <cs> <spi> <boards> <cmd> [<data>...]

Options:
<cs>      Chip Select (CS) to use: (0 | 1)
<spi>     Number of SPI bytes to transfer: (0 | 1 | 2 | 3)
          0 meaning that this is not an SPI transaction
<boards>  Integer ranging from 1 to 50
<cmd>     4 bytes (32-bit) long command (unsigned decimal)
<data>    8 bytes (64-bit) long data (unsigned decimal)

To ensure that the program is always executed with superuser privileges (possible security threat!):

$ chmod 4775 isoSPI
$ sudo chown root isoSPI && sudo chgrp root isoSPI

Examples

Commands are always sent to the IC LTC6813-1.

Sending commands to the IC LTC3300-1 (SPI > 0) is performed by an SPI transaction (from LTC6813-1 to LTC3300-1).

LTC6813-1

Send "Start Cell Voltage ADC Conversion and Poll Status (7kHz Mode, Discharge Not Permitted, All Cells)" command to all boards on isoSPI port 2 (CS 1):

$ ./isoSPI 1 0 2 56685676

Read "Cell Voltage Register Group A" from two boards on isoSPI port 1 (CS 0):

$ ./isoSPI 0 0 2 264130 0 0

Write "Configuration Register Group B" (GPIO6 Pin Pull-Down OFF: 1099511627776 or 0x10000000000) on three boards on isoSPI port 2 (CS 1):

$ ./isoSPI 1 0 3 2404766 72057594037993034 72057594037993034 72057594037993034

LTC3300-1

Send "Start Balancing Command" to one board on isoSPI port 1 (CS 0) by an SPI transaction (1 byte):

$ ./isoSPI 0 1 1 119612594 10014316694030852304

Send "Pause Balancing Command" to two boards on isoSPI port 2 (CS 1) by an SPI transaction (1 byte):

$ ./isoSPI 1 1 2 119612594 10009813094403507264 10009813094403507264

Send "Write and Execute Balancing Command" to two boards on isoSPI port 1 (CS 0) by an SPI transaction (3 bytes). In this example, cell 6 is discharged and cell 1 is charged (Balancing Command: 0xC02 or 0b1100 0000 0010):

$ ./isoSPI 0 3 2 119612594 9986886141864380864 9986886141864380864

Download

• isoSPI v1.0.1 - Latest binary release

$ sha256sum isoSPI
6f4c2d65629b5e4096543f3e0421dc2bdfe4309a991de7dbc617c6715db0b6f6  isoSPI

The C++ file isoSPI.cc was compiled on the Raspberry Pi Zero W with the following command:

$ g++ isoSPI.cc -o isoSPI -lbcm2835

Changelog

• v1.0.1
  • Adjusted the value of the series resistance (temperature measurement) to the nominal value.
  • Adjusted the nominal value of the series resistance (comment).
• v1.0.0
  • Initial release

License

Copyright © 2018 pro3E - Team4

This project is licensed under the MIT License - see the LICENSE file for details