Lisapeter's Fotothing

•A new Dell Latitude E6420 battery comes in a discharged condition and must be charged before use (refer to the devices manual for charging instructions). Upon initial use (or after a prolonged storage period) the battery may require three to four charge/discharge cycles before achieving maximum capacity.
•Keep Dell Latitude E6420 Battery cool. You can take a page out of the extreme gamer’s handbooks, and have your system perform more optimally by keeping it cool. Make sure your air vents (inflow and outflow) aren’t blocked by anything, which often occurs by poorly positioning your notebook on your lap (which is known to have some other side-effects too, by the way). Heavy CPU and memory use all contribute to heat as well, hence my comment on multi-tasking above.

•Keep your battery clean: It's a good idea to clean dirty laptop battery with a cotton swab and alcohol. This HEPS maintain a good connection between the battery and the laptop.

http://www.laptop-battery-store.ca/dell-latitude-e6420.html
http://www.laptop-battery-store.ca/dell.html