To have more 18650 cells, I thought to buy a used laptop battery and get the cells out. It turned out it was not a good idea. However it seemed to be a good offer. For 7 USD a used HP 12 cell laptop battery. I thought that it is not a recent model, but I have not expected this. It arrived with the post, it is a very massive and heavy piece.
It contains Sony cells, great!
Between the picture above and below after more than an hour suffering I was able to open it. It was built from almost a 1mm thick plastic and glued or melted together very well. I even had to use a chisel to open it. This was inside, I like the cell color.
There was no indication about the manufacture date on the outside, however there are signs inside. 2002 or 2003. Oh, no. It may be 13 years old?
The manufacturer put two thermistors into the battery, very clever. One is in the intersection of the left four cells, the other is on the lower four cell. It is better than in the other ones I opened, where only one thermistor was glued to one cell.
I have numbered the cells, so I will know which was where.
Controlling circuit:
The usual heat fuse and two chips which are anonimized.
But here we go! Let's measure the voltage. The three on the right had 2,27V, the other three packs had 1,73V... So I will not be able to use them for security reasons. If the voltage of a li-ion cell falls below 2,5V the inner chemistry gets damaged. The identification codes on the cells tell that they were manufactured in 2003. They are 13 years old! How can this be still around? And who would pay anything for this? I do. But you can't win them all, this buy was a failure. I cut off the two thermistors, so I have now 4 of them. I will take these cells to the recycling center where they already should be for 10 years. I do not wish to open such batteries, it was so hard and I won nothing, but experience.
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