Draw out the circuit yourself since you have the top off. I suspect it will
only be:

2x ---[cell,cell,cell,cell]--- in parallel, maybe with a few take-offs at
part way along for lower-voltage supply.

I dont think this will be so simple.

I have taken appart some of similar packs, but there is often quite
lot of electronics inside. One of the packs I have taken appart was
from a video camera and it definitely employed a microcontroller based
circuity.

I remamber that I wanted buy such cells alone few years ago, in order
to build some power supply for a national mountain day radio event. I
could not find any suppliers who were willing to sell me those cells
unless I would deposit complete engineering drawings of the charging
circuit for the resulting pack.

Ballancer is what they call the circuit in general, it is needed
otherwise there is a danger of overheating and explosion.