Don't know techy stuff but I have 15 Dell laptops in my team here all run constantly all day on AC with batteries installed, then batt only possibly when 'offsite'
When travelling to and from London on occasion my battery has lasted both way travel - about 2.5 hours though I've never checked batt level.
Never had a problem or noticed loss of performance. basically I would say it isn't a big issue with the batteries- as Baph says.
