First of all, I never ever had this happened before, probably because I began playing somewhere around october 2019, when the new battery system was already in place.
Now, to what has actually happened. I was trying to thin out zombie horde near apartment complex to get to the stairs without risking being surrounded and eaten. Had to move back to recharge my UPS and then I noticed something lying on the ground. “Hmm, looks like a battery, I wonder if that’s a heavy disposable one by any chance?”. Nope, it was this:
I wonder if I should make a bug report or this is some known obscure mechanics interaction. Playing on latest experimental, of course.
e: I have no idea where this item came from. There wasn’t even a zombie corpse on that tile, and this happened on a freshly-generated-on-the-latest-patch piece of map.