1.2 Definition of a Battery Management System
Three terms apply to the implementation of monitor and control functions in the energy chain. These terms are battery management, power management and energy management. As a rough indication, battery management involves implementing functions that ensure optimum use of the battery in a portable device. Examples of such functions are proper charging handling and protecting the battery from misuse. Power management involves the implementation of functions that ensure a proper distribution of power through the system and minimum power consumption by each system part. Examples are active hardware and software design changes for minimizing power consumption, such as reducing clock rates in digital system parts and powering down system parts that are not in use. Energy management involves implementing functions that ensure that energy conversions in a system are made as efficient as possible. It also involves handling the storage of energy in a system. An example is applying zero-voltage and zero-current switching to reduce switching losses in a Switched-Mode Power Supply (SMPS). This increases the efficiency of energy transfer from the mains to the battery.
It should be noted that the implementation of a certain function may involve more than one of the three management terms simultaneously. This thesis will focus on battery management and its inclusion in a system. A definition of the basic task of a Battery Management System can be given as follows:
The basic task of a Battery Management System (BMS) is to ensure that optimum use is made of the energy inside the battery powering the portable product and that the risk of damage inflicted upon the battery is minimized. This is achieved by monitoring and controlling the battery’s charging and discharging process.
Keeping in mind the examples of algorithms given in section 1.1, this basic task of a BMS can be achieved by performing the following functions: