Dell Latitude C540 - Manual (Page 36)

Health Gauge
The battery life span is largely determined by the number of times it is charged. After hundreds of charge
and discharge cycles, batteries lose some charge capacity, or battery health. To check the battery health,
press and hold the status button on the battery charge gauge for at least 3 seconds. If no lights appear, the
battery is in good condition, and more than 80 percent of its original charge capacity remains. Each light
represents incremental degradation. If five lights appear, less than 60 percent of the charge capacity
remains, and you should consider replacing the battery. See "
Specifications " for more information about the
battery life span.
Low-Battery Warning
NOTICE: To avoid losing or corrupting data, save your work immediately after a low-battery warning.
Then connect the computer to an electrical outlet, or install a second battery in the device bay. If the
battery runs completely out of power, hibernate mode begins automatically.
A low-battery warning occurs when the battery charge is approximately 90 percent depleted. The computer
beeps once, indicating that minimal battery operating time remains. During that time, the speaker beeps
periodically. If two batteries are installed, the low-battery warning means that the combined charge of both
batteries is approximately 90 percent depleted. The computer enters hibernate mode when the battery
charge is at a critically low level. For more information on low-battery alarms, see "
Power Management ."
Charging the Battery
NOTE: The AC adapter charges a completely discharged battery in approximately 1 hour with the
computer turned off. Charge time is longer with the computer turned on. You can leave the battery in
the computer as long as you like. The battery internal circuitry prevents the battery from
overcharging.
When you connect the computer to an electrical outlet or install a battery while the computer is connected to
an electrical outlet, the computer checks the battery charge and temperature. If necessary, the AC adapter
then charges the battery and maintains the battery charge.
If the battery is hot from being used in your computer or being in a hot environment, the battery may not