## 1 Introduction  
Due to energy waste and environmental damage, global warming is becoming more and more serious. Every country in the world is facing environmental pollution and oil shortages. Hence, electric vehicles that use batteries as power sources which do not emit exhaust gas to cause air pollution are gradually gaining importance in the market [1; 2; 3; 4; 5]. Based on these advantages, countries and major automakers all over the world are investing in the development and promotion of hybrid electric vehicles or electric vehicles. The battery module is the power source of electric vehicles and is one of the most essential components of electric vehicles because its capacity will determine the endurance of electric vehicles and its characteristics will determine their performance [6; 7; 8; 9; 10]. However, the price of battery modules is still high, accounting for a relatively high proportion of the overall cost, directly affecting the penetration rate of electric vehicles within the market. One of the reasons for the high price of battery modules is that their electrochemical properties are difficult to grasp. Nowadays, battery-related research, in addition to materials and electrochemical fields, generally includes monitoring of battery characteristics [1; 2; 3; 4; 5; 6; 7; 8; 9; 10], design of battery management systems [11; 12; 13; 14], estimation of state of charge [15; 16; 17; 18; 19; 20], estimation of state of health [21; 22; 23; 24; 25; 26], and so on. The estimation of the state of charge (SOC) of the battery is currently a very important research topic [15; 16; 17; 18; 19; 20]. In general, the state of charge is defined as the ratio of the current available battery capacity to the rated maximum available capacity, usually expressed as a percentage [18]. The most commonly seen conventional method today is to estimate the open circuit voltage method in conjunction with the Coulomb integral method. However, if the initial charge value determined by the open-circuit voltage method has an error with the actual SOC, the correctness of the calculation result will be affected [20]. In addition, the state of health (SOH) used to indicate the degree of battery aging is generally defined as the ratio of the maximum available capacity of the battery to the rated capacity, and is usually expressed as a percentage [21; 22]. Nowadays, some research concentrates on SOC and SOH for power batteries, which is an important research topic [21; 22; 23; 24; 25; 26] because the lithium battery is the most popular power source for electric vehicles (EVs). [PERSON] et al. [23] has developed a battery testing system to capture the related information of the battery by a capturing circuit and a loading circuit which is used to release battery energy by various constant currents (CC). In fact, the loading characteristics of the aforementioned method cannot be recycled, and are totally different from the actual work conditions, which are really not just constant currents. In addition to the aforementioned power waste issue, other problems include inflexibility, expensiveness, and complexity. Currently, there are two battery test techniques that are widely used in industry applications. The simplest is to transfer the extracted electrical energy from the tested battery to the designated backup battery [24]. Additionally, the electrical energy extracted from the tested battery is converted into alternating current (AC) form and then returns to the power grid by connecting with an inverter [25]. However, this system is much more expensive and complicated. The rechargeable battery is one kind of mobile energy storage device, and its applications range from consumer electronic products to the energy industry. As the battery number is increased in the energy storage equipment, the diagnosis of the battery is important and complex. In general, the battery diagnostics process includes at least two parts. First, the voltage, current, and temperature of all battery cells need to be detected and made sure to be normal.