The level of carbon emission is increasing everyday due to population growth and urbanization. We were dependent on fossil fuel as a source of energy traditionally for daily transportation. The growing concern on environmental degradation has led to alternate solution for fossil fuel-based transportation which is electrified transportation (E-Vehicle). Electric Vehicles (EV) are enabled by high-efficiency electric motors and controllers, powered by alternative energy sources thereby providing a clean, efficient, and environmentally friendly urban transportation system.
Components of E-Vehicle
The electric vehicle drive system includes, A Motor/Generator, Controller, Transmission(reducer) with Drive shaft, Battery, Battery Management System, braking system.
In 1830 (150 years back), the first EV was built with a non-rechargeable battery.
In 1874 (invention of lead acid battery), the rechargeable battery based EV was developed. A battery management system is an electronic system that handles a rechargeable battery.
Battery Management System
The Battery Management System (BMS) is playing a significant role in E-vehicle to ensure that the battery operates safely and efficiently. It manages the output, charging and discharging, provides notification on status of battery pack and protects batteries from damage. So, BMS is the brain of the battery pack.
The Li-ion batteries frequently used in an EV are expensive and susceptible to damages. The life span of the battery is important because it is the most expensive component in an Electric Vehicle.
The state of battery such as voltage, temperature, State of Charge (SOC) or Depth of Dis-charge (DOD), State of Health (SOH), State of Power (SOP), State of Safety (SOS), coolant flow and current in or out of battery is monitored by the Battery Management System.
This BMS calculates the secondary data (CCL, DCL, internal impedance, Charge stored or delivered, total number of operating time and total number of cycles), reports that data through CAN bus or any other communication protocols and controls its environment. It protects the battery from operating outside its safe operating area.
The state estimation of battery is required to enhance a battery’s protection and implementation. Fig shows the main degradation factors that affect battery condition.
Diagrammatic representation of battery degradation and aging
Battery state estimation includes four key states which shown in fig.
Estimation of Battery in four states
The BMS topologies fall under 3 categories:
|Sl. No||BMS Topology||Features|
|1||Centralized||Economical, Plagued by multitude wires|
|2||Distributed||Expensive, Simple to install and clean assembly|
|3||Modular||Compromise the Features and problems of both topologies.|