I can't recall what a glass-enclosed device is called which I think is a capacitive component with resistance. This component shows 11k ohm resistance and no difference in polarity, and checks equally the same with a DMM diode test.
This just looks like a small axial lead glass diode (~3.8mm long) without a cathode mark, copper colored dies at each end with a tiny gap between them.
The pack has three external terminals, of course (+) and (-) and a 3rd sense/charge terminal.
The component's place inside the battery pack is between a third external terminal and joined at a junction with the external negative terminal. The battery negative battery contact is connected straight to the external (-) terminal, and this device is between the negative terminal and the 3rd external contact. (not too swift at ascii art).