I install with sicurez installer. Yes using hard wire. I think 2 wire if I remember correctly. Anyway I’m just curious on why people not keen on using the parking mode for viofo? Any particular reason that I not aware of?

I prefer F800 Pro more as more discreet design, ADAS is accurate, built-in GPS

QX800 2K front and rear video and on-screen ADAS warnings. But need to purchase external GPS to use ADAS. Using SD card instead of micro SD card (SD card is easier to insert and eject while mounted than micro SD). Huge! IPS touchscreen. Cool security LED which won't use here

DR750S is good but lack ADAS function and need to purchase Power Magic Pro to use parking mode.

Above is my 2sen. You'll need to see which is your priority for a dashcam.
Where did you read that F770 using built-in battery?    

F770 is using a capacitor like all the other Thinkware models. All will hardwire to the car battery for parking mode.

Most Korean dashcams have stopped using built-in battery since 2010.

F800 Pro is the latest model.

If claim direct with Thinkware, will need to show proof of purchase.

Might also need to send back the unit to Thinkware.

You'll need to check with them and see.

Where did you buy/installed it?