Overriding default battery re-charge threshold

[RS <ravi2boxster gmail com>]

Hi All,

I am looking for ways to override the default battery re-charging
mechanism on my Thinkpad R61. The TP originally came with Vista business
and it had a utility where I could say something like "Only re-charge
when battery charge falls to 'x'% - for ex 50%" - the idea being to
prolong battery life and reduce re-charge cycles

looking for equivalent functionality on linux - ACPI hacks??

-Ravi