To quickly answer the question about balancing a battery pack, AS I UNDERSTAND IT (no expert here

, there is a small manufacturing variation between individual cells that means that cell capacities and "efficiencies" vary slightly. Over repeated cycles of charge and discharge, the effect of this variation is that cells in the pack can end up in different levels of charge.
When you come to use the tool and the pack discharges, one cell may empty first while the others still contain charge and continue to force current through the depleted cell. This is very bad for them, causes overheating, further reduces their capacity and eventually the failure of one weakest cell makes the whole pack unusable.
Balancing involves connections to each individual cell and charging or discharging them individually to restore them to the same state of charge. I think it relies on matching the voltages produced by each cell.It can be done by a small circuit installing inside the battery pack.
I once read that Bosch take the alternate approach and spend more up front on getting a closer match in the capacities of their cells, their packs have no balancing circuits, but imbalance doesn't become a problem during the typical life of a pack. The costs and lifetimes are similar to saving a few pennies on cells and spending on a balancing circuit.