There are several steps you can take to insure that you get maximum performance from your Dell Latitude E6400 battery:

Breaking In New Dell Latitude E6400 Batteries - new batteries come in a discharged condition and must be fully charged before use. It is recommended that you fully charge and discharge your new battery two to four times to allow it to reach its maximum rated capacity.
Preventing the Memory Effect - Keep your Dell Latitude E6400 battery healthy by fully charging and then fully discharging it at least once every two to three weeks. Exceptions to the rule are Li-Ion batteries which do not suffer from the Memory Effect.
Keep Your Dell Latitude E6400 Batteries Clean - It's a good idea to clean dirty battery contacts with a cotton swab and alcohol. This helps maintain a good connection between the battery and your portable device.
Exercise Your Dell Latitude E6400 Battery - Do not leave your battery dormant for long periods of time. We recommend using the battery at least once every two to three weeks. If a battery has not been used for a long period of time, perform the new battery break in procedure described above.
Battery Storage - If you don't plan on using the battery for a month or more, we recommend storing it in a clean, dry, cool place away from heat and metal objects. Ni-Cd, Ni-MH and Li-Ion batteries will self-discharge during storage; remember to break them in before use.
For Notebook Users - To get maximum performance from your battery, fully optimize the notebook's power management features prior to use. Power management is a trade off: better power conservation in exchange for lesser computer performance. The power management system conserves battery power by setting the processor to run at a slower speed, dimming the screen, spinning down the hard drive when it's not in use and causing the machine to go into sleep mode when inactive. Your notebook user's guide will provide information relating to specific power management features.

Battery care and use instructions

A. Your new battery comes in a discharged condition and must be charged before use. Upon initial use (or after prolonged storage period) the battery may require two to three charge/discharge cycles before achieving maximum capacity.
B. When charging the battery for the first time your charging device may indicate that charging is complete after just 10 or 15 minutes. This is a normal phenomenon with rechargeable batteries. Simply remove the battery from the charging device and repeat the charging procedure.
C. It is important to condition (fully discharge and then fully charge) the battery every two to three weeks. Failure to do so may significantly shorten the battery's life (this does not apply to Li-Ion batteries, which do not require conditioning). To discharge, simply run your device under the battery's power until it shuts down or until you get a low battery warning. Then recharge the battery as instructed in your user's manual.
D. If the battery will not be in use for a month or longer, it is recommended that it be removed from the device and stored in a cool, dry, clean place.
E. It is normal for a battery to become warm during charging and discharging.
F. A charged battery will eventually lose its charge if unused. It may therefore be necessary to recharge the battery after a storage period.

Overview

Always on the go? No more worries for running out of battery power! You can back yourself up with this Li-ion HP COMPAQ HSTNN-UB69 Laptop Battery for your Laptop. Lithium-Ion batteries are longer lived than conventional batteries and do not require replacement as often. There is no battery memory effect with this Lithium-Ion battery — you can charge the battery whenever you like without fear of reducing its charge capacity. Moreover, you do not need to drain the battery completely before recharging it. This product has been tested on Power Supplier systems. It is supported by Power Supplier Support when used.