Project Overview

[Andrew Ewert]

Welcome,

Here is a brief overview of what this project strives to accomplish:

Create a system where the cell level BMS boards gather the voltage and
temperature from each cell. The microcontrollers are powered directly
from the lithium-ion cell,
which is within the operating voltage of the PIC. The cell level BMS
boards will communicate with a supervisor over an optically isolated
bus. The bus will be bi-directional and will allow the supervisor to
program the cell level BMS boards as well as allow the BMS boards to
submit data to the supervisor. If the cell voltage goes above the
maximum allowed voltage, the microcontroller will activate PWM driven
bypass regulators attempt to lower the voltage by shunting 200ma
across a bypass resistor. The boards will also transmit all voltage
and temperature information to a supervisor and the supervisor will be
responsible for lowering the charge current limit to prevent
overcharge. The supervisor is responsible for coordinating the
balancing of the cells amongst the individual cell level BMS boards
and monitoring for weak cells, pack temperature, etc. The BMS cell
level board microcontrollers will go into a super low power sleep mode
to minimize pack drain when not in use.

The BMS boards are responsible for:
1.) monitoring the actual voltage
2.) monitoring the actual temperature
3.) listening for requests from the supervisor, reporting and
accepting data
4.) going to sleep after a pre-determined amount of time after the
supervisor has stopped communicating
5.) waking up on messages from the supervisor.

In addition, the supervisor is responsible for the following:

1.) monitoring the overall current flowing in and out of the whole
pack.
2.) Monitoring the overall voltage at the pack level and comparing it
with the expected level from the BMS boards
3.) Monitoring the temperature of each individual cell and reporting
an average temperature
4.) Maintaining maximum charge and discharge limits to be published
5.) Monitoring the balance of each cell (or cells) in the block and
coordinating corrective measures (shunting across the bypass
resistor.)
6.) Having a programmable section to allow the pack to be integrated
into a variety of applications - such as over a CAN bus.