Until now I have always left my battery in my laptop (IBM T40) when using it regardless of whether I charge or have the battery at 100% when on "real power".

Does it harm the battery ? I run it down to under 3% at least every 14 days. But most of the time I am on A/C power. Should I take the battery out ?

I would say that the battery performance has detiriorated by about 10% in 6 months use. Is this acceptable ?

Thanks for your input!!!