unofficially it can be charged off the older style micro-usb phone chargers at home, however, the quoted battery life of dashcams is usually nowhere near accurate (Mio, for example, say theirs last an hour, but tend to die after 15 minutes). Cant you use the included 12v car charger??
You can also use a mobile phone power-bank to power the dashcam in the car usually for however long you need if you can't use the car's 12v for whatever reason... while I was using an extra dashcam in my car where I didn't have a 12v socket free I used an old 2500mah EE powerbar, did the job for a temporary measure
The only useful point of the battery in a dashcam is for the moments after an incident where you might want to remove the dashcam from the car to get footage of the exterior of damaged vehicles...