Editing Psion netBook Battery Service (section)

== Why the controller board matters ==

'''Never wire cells directly to the pack's external contacts.'''

The board inside the pack manages the charge and discharge of the cells individually. Without it, three cells in series will drift apart in state of charge, and eventually one is overcharged or driven below its safe floor while the pack as a whole looks fine.<ref name="libatt" />

The machine's charger is more sophisticated than it needs to be for its original cells, and this is what makes rebuilding worthwhile: '''it measures the real pack voltage and charges until it reaches 12.6 V.''' It is not set for 1500 mAh cells specifically. Higher-capacity cells simply take longer to reach the same termination voltage.<ref name="libatt" />