I have one and I like it. Blackvue sent me a B-112 and a PMP for testing and review purposes. My car battery was getting really old so I started off by running with the B-112. It's a bit pricey, but I like it. With the DR650S-2CH, running the front camera only with wifi off, it's rated for 12 hours of runtime. With both cams on and wifi on for the cloud stuff, I get 9 hours of recording time. Once depleted, it takes 1 hour to fully recharge. I keep it under my passenger seat.
Here's a video clip of someone backing into my car and driving off, recorded with the DR650S-2CH and B-112.
It's bigger than my portable USB battery packs I use for charging cell phones and whatnot. I asked Pittasoft why it was physically so much larger and they said there's two reasons. Instead of the traditional Lithium Ion, they use Lithium Ion Phosphate for their batteries which is better able to handle the extreme temperatures inside a car. It also runs at 12.8V instead of 5V, but I would think the first reason would be the primary explanation. I'm not battery type expert though.
I also like that it has two USB ports which allows me to charge my phone while parked without having to have my car's electronics turned on and that's helpful too.
The primary thing I wish was different is I wish I could record for much longer periods of time. I often have my car parked for days on end and would ideally love to be able to record for several days if possible.
On a related note, I just got a brand new car battery and so I wired in the Power Magic Pro this week to see how things look with it. I'm curious to see how much runtime I get with it at different voltage settings. Hopefully I can get longer runtimes! *fingers crossed* I'm sure the PMP is a better value and while I'm not sure I would necessarily drop the cash myself on a B-112 if I needed to buy one, I really do like having a secondary battery dedicated to my dashcam that doesn't put additional strain and stress on my car battery itself.
Oh, speaking of the two, I asked Pittasoft about combining the PMP and B-112 to run off of both batteries. I know there'd be some losses with having one battery charge another, but they didn't recommend it due to the fact that the B-112 sucks a lot of power while charging and is too much of a drain on your car battery if it's charging without your car being on.
For testing purposes I tried plugging the B-112 into a portable USB battery pack to try and get more runtime (26,800 mAh at 5V versus 3,000 mAh at 12.8V with the B-112.) My B-112 was dead at the time and I wanted to see if the battery pack would provide wayyyy more recording time due to the fact that it offered 3.5x the capacity of the B-112. Having the full charged portable USB battery pack charge the B-112 and run the dashcam offered not 3.5x the recording time but rather a very modest 33% improvement in recording time. Instead of 9 hours I didn't get 31.5 hours. I got just 12 hours. This leads me to believe that there's a LOT of loss in trying to have one battery charge another battery to run a camera. Because of this, I would agree with Pittasoft that combining the PMP and B-112 isn't a good idea. Best to stick with one or the other.