## 1 Introduction  
Global warming is a climate issue of concern for much of the world. At present, excessive use of fossil fuels results in the emission of large quantities of greenhouse gases such as carbon dioxide. The emission of greenhouse gases into the atmosphere leads to higher global temperatures. To solve environmental problems, governments and global organizations have formulated energy saving and carbon reduction policies. The transport sector is one of the main sources of carbon emissions in most countries, among which the carbon emissions of passenger cars for road transport account for the highest proportion [1]. To reduce the energy consumed and carbon emitted by the transportation sector, the Taiwan government has formulated green transportation policies and advocated traveling on public transport instead of using passenger cars. The government has also promoted the use of low-pollution, energy-efficient, and intelligent transportation tools, such as the use of electric buses instead of diesel buses, to achieve energy savings and carbon reduction. The global vehicle industry uses advanced technology to develop alternative fuel vehicles that can alleviate air pollution and reduce energy consumption. Electric vehicles have the lowest energy consumption among all alternative fuel vehicles and are the focus of future global development. The power sources of vehicles have been analyzed to evaluate the energy consumption efficiencies of electric vehicles and gasoline vehicles. According to the 2019 Energy Statistical Annual Reports in Taiwan [1], the average power generation efficiency of the Taiwan Power Company is estimated to be approximately 34.25%, if crude oil is sent to power plants to generate power. Then, this is conducted to the battery packs of electric vehicles, and the resulting energy efficiency of electric vehicles is 20.1%. If crude oil is refined into gasoline, which is, then, used for internal combustion engines, the energy efficiency is 14.6% [2; 3; 4; 5; 6]. The comparison demonstrates that the energy conversion of electric vehicles is more efficient, which is beneficial for saving energy and reducing carbon dioxide emissions. The biggest difference between electric buses and traditional diesel buses is the vehicle's power system. An electric bus, driven by electrical energy, replaces the traditional diesel engine with a driving motor that is powered by a battery pack. The speed and torque of the driving motor are controlled by the motor controller. In the past, diesel buses used on-board diagnostics (OBD) to collect vehicle driving data via transmission cables or Bluetooth. Nowadays, electric buses perform management functions such as sensor data collection, charge/discharge control, and state of charge (SOC) estimation using a battery management system (BMS), and collect vehicle driving data through mobile networks [7]. To ensure good battery performance and extended battery life, electric buses must have their batteries properly managed and controlled [8]. Therefore, BMS has become a core technology for electric buses and, in recent years, has witnessed great improvements in the reliability of data collection, accuracy of SOC estimation, and monitoring and management of the electric current to prevent battery damages caused by voltage overload [9]. The function of BMS is to monitor the operating conditions of vehicle batteries to ensure driving safety. With this system, the batteries are not damaged, do have their service life reduced, or, under extreme conditions do not cause accidental explosions or fires that endanger safety. The battery represents the largest cost of an electric vehicles [10]. Management via the effective use of the data collected by BMS enables the vehicle operation to optimize benefits. Eco-driving can slow the discharge rate, which helps to reduce energy consumption while driving. It also protects battery safety and extends battery life to ensure the operational advantages of reduced battery and driving costs.