Sanyo SCP-4000 - Manual (Page 85)

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Replace the battery when it no longer provides acceptable
performance. It can be recharged hundreds of times before it
will need to be replaced.
Do not store the battery in high temperature areas for long
periods of time. Follow these storage rules:
Less than one month: -4˚F to 131˚F (-20˚C to 55˚C)
More than one month: -4˚F to 95˚F (-20˚C to 35˚C)
Driving
Using a wireless phone while driving is illegal in some states and
countries. For your safety, become familiar with the laws and
regulations for your area, and pull off the road and park if you
need to make a call.
If you must use the phone while driving, purchase
and have installed the optional hands-free car kit
or the headset.