I had my dashcam (750/770) constantly requesting to format the sd card when first started. Initially, I thought the internal battery was dying but I took a look at the recordings and they all contained the correct dates and time. So the complaining from the dash cam was about the SD card. I removed the SD card and inserted it into a PC which was able to read it. I did a complete format of the card (NOT a quick format) and loaded the dashcam firmware and powered it up. No complaints after one restart so far, I'll see how it goes.
I did open up the dashcam and tested the internal battery on a multimeter, which showed 2.83 volts. So it's OK.