Simple 18650 remaining life test

[bob_ninja]

Not sure if this was explored in the past.

When I recovered 18650 cells from laptop batteries I performed a simple test to check which have some life left. I charged them to full, then left idle for few weeks. Any cell below 4V was discarded. Remaining cells serve me well on low power lights. However I have couple of lights pulling 1.5A to max 4A. Needless to say this is a challenge for many tired cells. I want a simple test to see which cells still have a lot of life left and can handle 2A or more.

Here is test setup I am thinking about using simple DMM:
Charge to full
Idle for 1 month
Check voltage, pick 4.1V+ cells
Use them in the light pulling 4A for 10min
Check voltage
Leave idle for a day
Check voltage
Pick highest voltage cells - these can handle heavier loads

Simple test - Is it useful?

 

[SilverFox]

Hello Bob,

I believe you are trying to measure voltage under load.

If you figure out a resistive load (like a particular bulb) that simulates a 2 amp load, you could simply measure the voltage under that load. Weak and aged cells will register a lower voltage and you can put together a look up table for your test to sort cells.

Tom