Battery Using Tidbit
Most battaries that favor a constant charge and recharge capacity work in two different forms. Your standard Ni-Cd or nickel cadmium battery is a slow drain slow charge type battery, a complete drain and recharge is a standard that most of us know.
Not the case with Li-Ion, the lithium Latitude D520 Battery , and newer Metal Hydroxide batteries work better and last longer using the 100-40-100-20-100-40-100-40-100-20% recharge plans. On your initial charge of 100% charging you let the battery drain to 40% and then recharge to 100% and then the second depletion to 20% and back to a full recharge cycle. This helps maintain the battery condition and in some aspects the "Brain" of the Latitude D830 Battery so to speak is set in motion and maintains battery health througout time.
Another item to remember is that when you plug in your laptop, and the indicator says fully charged, the battery is still being used in most cases and recharging. A good note is to remove the battery while in use of a power outlet and set aside until going mobile. This will also help prolong the battery. Hope this helps anyone who may be having to replace Latitude D620 Battery often.
(P.S.) also good for cell phone usage (have had my phone for 4 years with no problems in keeping a full charge of battery life for at least 2 days, havent replaced the battery yet).