Because I use 2 x 2 channel cams ( 4 cams ) if I use the power magic pro I'm lucky to get 5 or 6 hours before it powers off , I need atleast a guaranteed 9 hours to be sure I'm fully covered . With the battery packs I get easily 12 hours even more in park mode , this is with motion detection on high , if I turn the sensitivity down then obviously longer . Luckily for me my car is garaged at night so I turn the system off when I get home , this means my battery's are fully charged after my drive home so if I only have a short drive the next day I still get a good full day out of it . I have the Cellink-Neo in the other car that allows you to check how much charge it has via a phone app , from memory I think a short 5 to 10 k drive it gets up to about 70% . In that car I have 1 Thinkware 2 channel and I bought 2 single channel I use for the sides , the 2 single channel aren't as power efficient as the Thinkware so with 1 battery she probly gets about 3 to 4 hours . The single channel cams are DDPai 3 and are quite good for a cheap cam if you buy 2 of them , they have inbuilt memory and you view from your phone over wi-fi same as the Thinkware and Blackvue but no need for a memory card and no need to turn wi-fi on on the cam.
Another thing with the Cellink is if you have an AC to DC 12 volt adapter pack with a 12v cigarette socket you can fully charge it up if need be it will also charge directly off your battery when parked through the 12 volt socket in your car , my wagon rear socket has constant power if I need but never have