Canon VIXIA mini Instruction Manual page 231

Do's and Don'ts
Built-in Rechargeable Lithium Battery
The camcorder has a built-in rechargeable lithium battery to
keep the date/time and other settings. The built-in lithium battery
is recharged while you use the camcorder; however, it will dis-
charge completely if you do not use the camcorder for about 3
months.
To recharge the built-in lithium battery: Insert a fully charged
battery pack into the camcorder or power it using the optional
CA-110 Compact Power Adapter. Then, leave the camcorder 24
hours without turning it on.
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