This may help, http://www.internettablettalk.com/fo...ad.php?t=20117

bun

Like tricle-charging, partially recharging a LiIon battery has no ill effect whatsoever, the reason being the "clever" charging circuitry built in.

Deep discharges (until the cutoff point of the device) are very harmful though if done repeatedly, although some people advize to let a LiIon discharge completely occasionally(again: only until the device it's in shuts down!). Apparently it helps on keeping an accurate battery gauge. LiIon battery gauges are software-based and said to not cope well with partial discharging (which is the best way of using a LiIon battery, ironically), so they need a "reset" ever so often.

Sources say this should be done every 30 full charge cycles (or the rough equivalent of partial cycles). Personally I don't bother, as I never let my batteries run dry anyway.

(FYI, my 770 and N800's batteries show no noticeable decay as to date. I've had my 770 since early 2006 and it's still used almost daily as a dedicated ebook reader)