Multicell Voltage Monitoring for Lithium Battery Pack in Electric Vehicles

This electric vehicle battery management project monitors the individual voltages of a 4-cell series 18650 lithium battery pack using an Arduino Nano. In a series string, each cell sits at a progressively higher electric potential relative to ground, meaning a standard microcontroller analog input cannot directly measure the upper cells without exceeding its voltage limits or shorting the stack. To solve this, the circuit employs OPA4197 operational amplifiers (or an LM324 alternative) configured as precision buffers and differential amplifiers. These high-voltage rail-to-rail op-amps scale and shift the floating voltages of the individual cells down to safe levels that match the analog-to-digital converter (ADC) range of the Arduino Nano. Resistors such as 1K units are used in the op-amp feedback and input networks to set the correct gain and biasing. Once the conditioned analog voltage signals are safely translated, the Arduino reads them via its analog input pins, computes the individual cell voltages, and updates an LCD screen to display real-time metrics. The entire circuit is routed on a custom PCB designed in EasyEDA and assembled with female headers and connecting cables for reliable modularity.