Overview:
Electronic Load PCB designed to discharge 21700 lithium-ion battery cells at a constant discharge current. Capable of monitoring cell voltage, current through ESP32. Functions by using op-amp in negative feedback to drive the gate of an NMOS to maintain constant voltage across power resistor bank.
Motivated by need to characterize discharge curves over State of Charge and temperature to gather data for Formula Electric at Berkeley's battery pack development team. Provides cost effective solution and simple solution to purchasing discrete electronic loads or outsourcing cell tests.
Future improvements include switching to STM32 family of MCU, integrating a charging circuit, temperature monitoring, and cooling to develop a scalable, automated cell cycling PCB, concept of which has already been demonstrated in prior IoT device project.
Inspired by and grateful for this MIT Motorsports article: https://fsae.mit.edu/blog/2019/10/30/my19-cell-cycling
Proof of Concept:
MecEng 100 Final Project: integrates resistor bank, power supply, relays controlled via NMOS from ESP32 to cycle 18650 lithium ion cells at variable resistance. Uses K-type thermocouple and shunt resistors to monitor temperature and current. Capable of automated cycling and controllable using phone widget remotely.
The final goal of this project would be to incorporate the constant current discharge circuit with the safety and data collection features of both devices into one well-organized PCB.
P.S: In the group photo, I'm the one in the Stanford jacket holding the red PCB. The story behind that jacket is, at my first Big Game, I wore that jacket since Stanford had been undefeated for 7 years straight at that point, but on the off chance that Cal won, I had Berkeley merch under that jacket. Lo' and behold, we won, and I've worn that jacket as an anti-good luck charm ever since.