Used Lithium Ion IMR18650 HB7 1500mAh LGDAHB71865 Electrical evaluation

[Kiriakos GR]

The only way to get in your hands today these LG IMR18650 cells is due a Black and Decker rechargeable vacuum cleaner.
I am now also aware of this problematic electrical application.

In theory Black and Decker made a product that actual current that the motor use is approximately 5 ~ 6A.
Samsung made a special Lithium Ion cell that can tolerate up to 10A of load (fast discharge).
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But Samsung forgot to inform the industry that when their cells deliver 5A of constant current for 10 minutes,  they get warm at 55 Celsius.
This is tremendously stressful condition for any 16850 cell no matter if they are named as magical LG special version.

Common complain is that  these batteries does not last more than two years in a such Black and Decker rechargeable vacuum cleaner.
But my discovery is that a single failing cell,  this it does stop the vacuum cleaner prematurely.
There is inside an electrical voltage monitor circuit per cell,  if one of the five cells comes down at 2V,  the controller cut off the motor.

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I am currently performing discharge testing at all five LGDAHB71865.
All five batteries were charged at 4.23V
Four of five cells measured 43~45 mOhm of internal resistance while the fifth measure 58 mOhm.
LG specification = 30 mOhm
 
My test bed this can test four cells at a time, I did select the four cells with 43~45 mOhm of internal resistance.
In my surprise after ten minutes at 5A load one of the four cells this collapsed down to 1V, while the other three kept delivering at 3.2V
I did disrupt the test.

Now I am going to test the three non problematic cells by adding the fifth which this measure 58 mOhm.
As it is proven so far,  the internal resistance its not the major problem here.

These LG cells at fast discharge they become unexpectedly warm (they run extremely hot).
This sudden change from room temperature at high temperature of 50C within 10 minutes, this is the smoking gun.

Any smart company, instead to build chemistry that can survive at high temperature they could simply use 2500mAh instead of the basic 1500mAh.   

About my self, I am after to discover the number of surviving cells so to reuse them at lesser demanding applications.
The second test that I am going to run this will be very informative.     

[Kiriakos GR]

Never expected that my second test will end that fast.   

The fifth cell: LG IMR18650 this collapsed at 5A within a minute of use.

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Semi final results:
Cell  1 = heavily damaged
Cell  2 = significant capacity loss
Cell 3,4,5, still some capacity in them.

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I am now charging again all four that still show as usable, and the next testing will be per cell capacity test.
LG advice about capacity evaluation this is setting a load of 300mA with End voltage(Cut off) 2.5V

[Kiriakos GR]

Final damage assessment of five abused LGDAHB71865 for two years.  

Cell A = 1330 Ah / or 4.333 Wh  (discharge duration at 300mA)  4:27 
Cell B = 1243 Ah / or 4.435 Wh   (discharge duration at 300mA)  4:06
Cell C = 1289 Ah / or 4.627 Wh   (discharge duration at 300mA)   4:19
Cell D = 1067 Ah / or 3.579 Wh   (discharge duration at 300mA)   3:34
Cell E = Dead

Cell E & D were first and last in this Cells is series battery pack.
Cell  A,B,C approximately 12% capacity loss. 

This test results are extremely useful, by the numbers every even damaged battery pack it still has three to four surviving cells that can serve at other applications.

Tip of the day, ask help from service center so them to rebuild your battery pack,  but get back the used lithium cells from the old pack too.