## Proposed System
### Performance and Evaluation  
In this section, the potential of improved MTC is explored and evaluated with the usage of the proposed BMS included in. Below is the explained the operation and use of the MTC. The new MTC software V.5.1.0 has higher voltage operation compared with the previous version V4.2.1 [8; 9], which was limited up to 9 V, where the new one can operate up to 12.6 V. This improvement allows the use of 3S4P BMS configuration. Also, the interface and menu are changed by giving more freedom in terms of battery selection, type of waveform operation i.e., Constant Current Constant Voltage (CCCV), pulse or arbitrary for different combinations of battery connections such as in series or parallel. The details are shown in Figures 11-13 in the Appendix A. The user can insert the information such as the upper and lower voltage limits of the test battery for safe operation. Then, test condition such as frequency and the current value is also entered. Regarding the test condition of the proposed MTC is the same with the previous system, which is set by the controller with a rotary encoder, and the conditions are always displayed on the liquid crystal display (LCD) during the test. At that time, the charging and discharging circuit are controlled by a feedback system based on the voltage and current data. The data obtained from the test can be saved in an SD card and displayed graphically. Figures 3 and 4 show the system performances when a Li-Ion battery cell is charged and discharged by the system. Figure 2: System appearance (during operation for battery pack 3S4P or for single cell test). The battery current can be controlled by the built-in microcomputer or an external oscillator, as shown in Figure 2. For example, the current waveform is sinusoidal with an amplitude of 3 A and a frequency of 1 Hz. The maximum difference between the target and measured current is in the range of 120 mA, which indicates the accuracy of the developed simulator. From the measured voltage and current, the battery characteristic can be obtained. For example, the capacitive characteristic of the internal impedance is obtained from the phase difference, and the impedance of 130 m\(\Omega\) is obtained from the voltage fluctuation amplitude of 400 mV and the current amplitude of 3 A. The validation of the characteristics in a high-frequency region, the arbitrary waveform having the current amplitude of 1 A with the frequency of 1 kHz is entered as the external signal input as explained in Figure 4. In this example, a delay of 130 \(\upmu\)s is observed at the switching from the charging to the discharging. It is the required time for switching the operation of charging management ICs in the charging and discharging circuit controlled by the microprocessor. Regarding the BMS circuits and components, BM3451 IC commercially purchased component is used for the proposed BMS circuit. The BM3451 continuously works to monitor each cell's voltage, the current of charge or discharge, and the temperature of the environment to detect over-charge/discharge, overcurrent, short circuit, and over-temperature, etc. Besides, also it can change the protection delay time of overcharge, over-discharge and discharge overcurrent by setting the external capacitors. The BM3451 provides external bleeding for the cell-capacity balance function to avoid unbalanced capacity between each cell. Thus, the batteries can work for longer. In Figures 5 and 6 are shown the block diagram of BM3451 with three-cell application including balance function. Figure 4: Voltage response of a Li-ion battery to an arbitrary current of 1 kHz frequency. Figure 3: Voltage response of a secondary Li-Ion battery based on sinusoidal current. The extended function module embedded in the BM3451 ICs makes them work for an increased number of battery packs with multiple chips, and they can protect 6-cell batteries or even more than 6-cell batteries.