Just had a though, what if somebody uses these on a rechargeable cell, and put it into the charger with the Batteroo still connected, and it is one of those lovely low cost Big Clive style chargers, which use a capacitive dropper to charge the cells. Wonder what will die first, the chip or the capacitors, and just how much current can a NimH cell provide into a shorted stainless steel clip.
Was also looking at places that would fit a Batteroo, and aside from a battery charger, that takes both AA and AAA that uses a spring clip, nothing will fit them, some even are fussy about taking certain cells, as the positive pip is too short. And yes, I do have a CO detector ( $5 from China delivered, not seen them locally at all, so I ordered 2, must look inside the one) that uses 3 AAA cells ,and it came with OHL Fong Kong blanded ones, which seem to work, though I bet they will be making a loud beep sometime, and I will replace with Energiser ones.