[BrianG]

Not sure about the zippy packs, but Turnigy's have a PCB which the tabs are soldered to (instead of soldering the tabs directly together). This makes disassembly MUCH easier if needed, but the traces that go from tab to tab may not be large enough to handle the current. I know on some older 3s packs, there was a trace that was too small and would blow. Since the balance wires are physically attached to the cell tabs, it makes sense that the balancer would see all the cells, but if a trace is blown, the series connection for the main leads would be broken.