Hi,
the point in this is, that the battery system is balanced.
As my english is poor, I just write shortly and let you read this website that can explain this more better.
When forming large systems with multiple battery, you should notice that they will reload and discharge unevenly if not connected correctly.
If not connected correctly, this will become more and more problem as the time passes, couse of the different resistance of the connecting wires.
Here is a longer explanation of this, good luck:
http://www.smartgauge.co.uk/batt_con.html
