In this study, the battery pack and ESP32 microcontroller-based battery management system (BMS) design for the electric bicycle have been carried out. The software updates were realized when the battery pack was in the box, thanks to the built-in Wi-Fi feature of the ESP32. The voltage values were read precisely, and a stable BMS was created with a 12-bit ADC-based ESP32 controller. The battery had temperature control from 7 different points. The temperature data was received from DS18B20 digital temperature sensors, and the charging current was cut off when the threshold value was exceeded. At the same time, the ACS712 5A current sensor was used to determine and prevent the excessive current draw. The charging current was defined as 2A. BMS cuts off the charging current to protect the battery pack when the charging current exceeds 3A. The resistor used for passive balancing in BMS was isolated from the ESP module with the KPS2801 optocoupler. The voltage of the battery pack was charged from 3.7 V to 3.85 V in the real-time test. The charging process continued for one hour, and the voltage changes of each cell were obtained in 10-minute periods. It was observed that all cells were charged in a balanced way at the end of the charging process. Thus, the charging process of the designed battery pack was carried out successfully through the designed BMS.