These charts and statistics are live and update in real time as I add data for newly tested cells.

Cell extraction

I try to keep up steady progress in the relentless task of extracting 18650 cells. I need 70 for the next battery build stage.

After ensuring safety, the most important metric for this project is cell capacity. I’m testing capacity by discharging from 4.2 V down to 3.2 V at 1 amp.

There are various ways that cells can fail my tests before this capacity check (heating during initial charge, visible corrosion, etc), and I am encoding these cases as nominal capacities below 1 mAh. These are not included in this histogram.

Although it won’t effect the final battery, I’m also interested to follow the fraction of reclaimed cells that pass my tests with a “good” verdict. This is based on capacity, with thresholds:

  • “good”: capacity ≥ 1800 mAh
  • “poor”: 1000 mAh ≤ capacity < 1800 mAh
  • “dead”: capacity < 1000 mAh

The “success” rate of about 40% has remained fairly steady.


I have live logging of my charge process. During the day these charts update in close to real-time.

Pack Balance

I’m not yet actively balancing the packs, but I’m monitoring their voltages to keep an eye on the battery balance. It is remarkably stable!