7C. Using the Built-in BatteryThe unit has a built-in, non-replaceable, rechargeable battery. Charge the built-in battery before using it forthe first time. The normal charging time should be completed within 3-4 hours. The red charging light willgo out when the built-in battery becomes fully charged.To Recharge the Built-in BatteryWARNING• The built-in battery should not be exposed to excessive heat such as sunshine, fire or the like.• The built-in battery presents a risk of fire or chemical burn if mistreated. Do not disassemble, place near asource 212°F (100°C), or incinerate.• Dispose the unit with built-in battery properly. Environmental problems must be considered and localrules or laws governing the disposal must be strictly followed.CAUTION• The built-in battery can only be recharged when the unit is in CHARGE mode while using the ACadapter.• The built-in battery cannot be recharged when the unit is in power ON mode.• Do not recharge the battery in the vehicle by using the car power adapter.• When the built-in battery power is low, "BATTERY LOW" will appear on the screen and the unit will stopplaying.• Recharge the built-in battery when you are ready to use it again.• While using the built-in battery, the environmental temperature should be 41°F (5°C) to 95°F (35°C).• To get the longest service life of the built-in battery, charge at indoor temperature.