300W 30V10A 18650 Lithium Battery Capacity Tester/Meter Resistance Discharge Electronic load TTLserial port Modbus Communication - AliExpress
Vastarry 180W DC Electronic Load Tester, USB Load Tester, Lithium Battery Capacity Tester, Color Screen Data Monitoring, Constant Current and Constant Voltage, etc. 4 Working Modes: Amazon.com: Tools & Home Improvement
Finally have a decent working battery capacity tester. : r/arduino
18650 Lithium Battery Capacity Tester using Arduino
I Made a Battery Capacity Tester with Constant-Current Discharge Control : r/raspberry_pi