The battery is a Li-ion Battery which requires as a pack that the cellsall have the same capacity.
In the original pack is a balancer which takes care that all cells get the same load.
Li Ion can react in burning exploding etc. so be sure what you do with them because the 3rd connector is for balancing.

@ntwk2001 pls give us a longrun feedback pls.....and pics.
How long is the power up time of yours????

Best regard from Germany trace