A lot of battery controllers are intentionally designed to make the batteries unusable if the cells are removed for even a moment. Sometimes the controller uses

A lot of battery controllers are intentionally designed to make the batteries unusable if the cells are removed for even a moment. Sometimes the controller uses a volatile ROM that wipes itself when it loses voltage, other times there's software actively looking for it and stopping the controller from working when detected. It's very consumer unfriendly in general for batteries that the consumer supposedly owns, but for batteries that are more loaned property like this it's a reasonable anti-tamper system.