Fujitsu TeamPad PBT7500-16 Operation Manual page 9

If the battery pack is not correctly mounted or defective at the charging, the LED
flashes in red. Correctly mount or replace the battery pack.
The capacity of the battery pack decreases over time. The time which the battery
can be used shortens as its capacity decreases. When the capacity of the battery
has decreased to the point there is a significant reduction in service time despite
normal charging, the battery is reaching the end of its service life. Replace the
battery pack in this case. A battery pack lasts for about 500 charges. The service
life of the battery pack varies depending on the ambient temperature and the
operating environment of the device. If the battery pack is not used at room
temperature (between 10° to 30°C), it may reach the end of its service life before
being charged 500 times.
The battery pack can be charged before the LED of the battery pack starts flashing
in red. The battery pack can also be removed from the charger before charging is
complete.
A battery pack that has been stored for a long period of time needs to be charged
before it is used.
Dispose of any used batteries, according to the instructions of the Fujitsu service
personnel.
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