Battery Capacity Checker

Discharge 2 Li-Ion cells from >4.1V voltage to 2.5V while recording the discharge profile and cell capacity. Discharge process can be started by pressing a momentary push button switch. A red LED lights up to indicate that the discharge process is still continuing (2.5V cut off has not been reached).

Circuit:

Schema:

Main components:

• 2x 50A, 50V, 0.022 Ohm, Logic Level, N-Channel Power MOSFET: F50N05L

• power resistors: 2x Ceramic 1 Ohm, 10 Watt (shunt); 2x Aluminium 3.3 Ohm, 25 Watt (load)

Note	Many other N-Channel MOSFET’s can be used.

Breadboard:

https://goo.gl/photos/qm96asJ2DXB2iUNHA

Example Result

1500mAh cell:

y-axis blue: cell voltage
y-axis red: cell capacity
x-axis: time in seconds

https://goo.gl/photos/hopcskTPDCRb9MaL8

Credits:

Single cell circuit:

1) http://AdamWelch.Uk

2) http://learn.linksprite.com/project/diy-arduino-battery-capacity-tester-v1-0/