Safer - 18650Battery tester


That one is a classic : How to test salvaged 18650 batteries and their capacity.
My implementation is derived from a very classic one as found on instructables, with 2 differences :

  • I'm using an INA219 to measure the current. That way i can use different load resistors to speed up the test, no need to calibrate anything.
  • There is a TP4056+DW01 between the circuit and the battery.
The TP4056 role is to add security (short circuit, too deep discharge etc...) and later on to automatically re-charge the battery at the end of the test. 
I dont have P-Mosfet available to do it at the moment, but is is easy enough to do.

/!\ the TP4056 disconnect the negative when it enters in security mode
/!\ When in security mode, you have to connect the usb charger to reset the circuit
/!\ To be on the safe side, the battery discharge will stop at 3.2 Volt

So at the moment, due to lack of P mosfet, you have to physically unplug the arduino and plug the TP4056 to load the battery.



The program also outputs csv progress , so that you can draw some diagrams at the end , such as that one (load vs voltage under load) :


The end result looks like that :




During discharge, the red led will be on and  the screen will display : Voltage, current, time elapsed, total capacity and approximate load of the battery.





It takes ~ 2 hours with a 6.6 ohm power resistor (homemade from vaping gear).


Source code : Arduino micro source code




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