Sena Bluetooth SM10 v1.1 User's Guide - Manual (Page 20)

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BATTERY INFORMATION
The SM10 has an internal, non-removable, rechargeable
battery. Do not attempt to remove the battery from the device
as you may damage the device. The battery can be charged
and discharged hundreds of times, but it will eventually wear
out. Recharge the battery only with Sena approved chargers
designated for this device. Use of an unapproved charger may
present a risk of fire, explosion, leakage, or other hazard.
Always try to keep the battery between 15°C and 25°C (59°F
and 77°F). Extreme temperatures reduce the capacity and
lifetime of the battery. A device with a hot or cold battery may
not work temporarily. Battery performance is particularly limited
in temperatures well below freezing.
Do not dispose of batteries in a fire as they may explode.
Batteries may also explode if damaged. Never use any charger
that is damaged. Operating times are estimates only and
depend on the devices used together, features used, battery
age and condition, temperatures to which battery is exposed,
and many other factors.