Li-Ion batteries with 3 connections
Unless you know the configuration of the battery pack I would suggest you recycle the entire battery pack in a responsible manner.  It is dangerous to connect batteries incorrectly.

It is common to extend the life of a secondary battery pack by balancing the charge between individual cells. Here is an example of passive balancing for a 2 cell battery pack:



It does not sound intuitive to drain the charge off an individual cell to extend the pack's life.  But it works.  

It may be more intuitive to think about active balancing where the charge is moved from the most charged cell to the least charged cell.  However, active balancing is much more complex to implement.