This latest entry into the battery pack market is an excellent investment for anyone who wants to protect their parked vehicle without ever having to hardwire their dash cam. I love the slim profile, USB ports, and, of course, large capacity. I use the BI-750 to power my Viofo A129 Duo while parked. I also have a Cellink Neo pack (made by the same Korean manufacturer) to power my Thinkware u1000 in parking mode and, although the older battery pack does a great job, the BI-750 raises the bar considerably.
I should mention, too, that the BBMC folks give amazing support. I had ordered the cigarette socket output (because I hadn't researched enough or asked pre-sales questions) and soon learned that it didn't support parking mode on the Viofo. The customer service person I finally called, was most helpful and informative. She immediately had the correct cable sent out and now the Viofo parking mode performs flawlessly. BTW, she also cheerfully generated a refund for the price difference on the BI-750 that had gone on sale. As promised on their website, BBMC truly did honour their price reduction guarantee. I wish I had known about these guys earlier - they would have saved me a lot of time (and probably $$, too)!