In search of a solution to the same problem with the BV9000, I ended up here.
The device has a shorter battery life than that
A7 of my son, because alone Bluetooth uses more than 30% of
Batteries, although sometimes it turns off easily. I loaded the device 16 hours ago and went to sleep. This morning Bluetooth was off, but had already consumed more than 10% battery. Currently Bluetooth has already consumed 23% (calculated 943 mAh) and the day is not over, it's just midday.
After I got that on Amazon, I set up the device as "new", so no backup recorded, did the OTA updates and then
made a factory reset. When I noticed the problem, I have made a factory reset again. Unfortunately, no improvement.
Turning off Bluetooth is unfortunately not an option, because I use it in the car and a smartwatch that would otherwise be deprived of its functions.
My Firmware Version is BV9000-FHD-Blackview-V0.5-20180119