You may be right on a “fatal discharge” circuit being built in to these packs, I don’t know.
I have always assumed that the reason there are so many like new packs in the recycle bin is because the store or customers make the mistake of fully discharging a pack and leave it for an extended time in that state.
With all the monitoring circuits in the BMS board, there HAS to be some parasitic drain, and if there is, it wouldn’t take much time for the pack in a fully discharged state to drain further to a point of no return. In other words a permanently damaged pack.
Take a look at this discharge curve I pulled from the thread
I had to estimate the capacity of an 18V drill pack, here is how I did it.
From that thread, the area under the curve is approximately the same as the area bound by the red lines and represents the Amp-Hour capacity of the pack. The horizontal red dashed line is the cutoff voltage.
Now notice the blue arrow, it points to an area under the curve to the right of the vertical red line that is bounded by the discharge curve.
It is a very tiny area!
The graph only goes down to 2.3V, but as you can see, if you were to continue the discharge curve any further, you wouldn’t increase that area by very much at all. There is very little capacity past the shut off voltage.
What this means is that if there is any parasitic drain in a pack, leaving a fully discharged pack in that state can kill it!
That is why I believe I find so may “like new” packs in the recycle bin that are dead. Most come, I believe, from tools on display in the stores.