Battery Management System

Layout
Depending on the application the term "Battery Management System" is used for different configurations. But it is common to all applications to collect data of the battery (voltage, current, temperature) and that there is a main power-switch to disconnect the battery from the load (self-protecting). To perform these tasks we need a controller for the monitoring and the hardware to perform the measurements (sensors, amplifiers, filters) and the power-switches.
BMS: layout

The schematic layout shows on the left side the battery stack ("batt.") and on the right side the load ("load"). In between is the (simplified) battery management system. The BMS (blue) has a central controller (green), connected to the left to the battery (brown lines). To the right there are connections to the power-switches (red).

The functional blocks are:

  • U: voltage monitor
  • I: current monitor
  • PS: battery main power-switch
  • D: discharge control

The "D" power-switch is connected to a resistor, limiting the discharge current.

The controller reads the sensor signal and thus monitors the battery. It can detect dangerous conditions and initiate the battery disconnect.

There are further components, not shown in the schematic diagram. Examples:

  • Data storage: It is interesting to record the measured data for an off-line analysis
  • Electronic parameter storage: It is useful for the main system to know exactly what type of battery is used. That is the purpose of the parameter storage memory, holding a variety of specific data. The data are stored during the production process.
  • Real-time clock (RTC): Obviously, the time marks of all events are important for the analysis of the data.
  • Telemetry: In many applications the BMS in not an isolated device, but is in close contact to the supporting main system. The main system processor may be interested in the state of the battery. The BMS can inform the main system about potentially critical situations so it can prepare countermeasures.
  • Charging unit: There are BMSs incorporating the charging unit for the battery.
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