850 Battery Life - OUCH!

8-9% per hour is the normal consumption with or without active navigation 

I don’t know how DCRainmaker het almost 19h with 30% brightness? The estimate hours given by the edge 850 is far from reality.

it says 45h at 40% brightness and backloght stys on…but after 3h ot drops to 28h

battery life estimates when using auto-brightness will never be accurate - it has no way of knowing what light conditions it will be in and hence what the screen brightness will be. i guess with all previous generation devices the screen was not such a massive proportion of the drain so it was possible to give a reasonable estimate but with the x50 the screen seems to eat most of the battery so if your ride is all in bright sun then the drain is going to be really high just to keep it readable and garmin seem to have completely failed to consider that.

with a fixed brightness it should be very accurate though - seems like they've completely screwed that one up, will probably be a software update in 6 months to fix it once they get through all the other likely bugs

I'd never paid attention to the Previous Models section until I saw your post.  Looking at it, there are numerous items marked Discontinued, with no price listed.  There are also some items not discontinued, but without a price, and there are several with a price listed.

I'm guessing that where there's a price, it means Garmin still has some, and will sell them to us.  Those without a price likely means Garmin is out of them, but they are still supported by Garmin.

I don’t know how…but after 18-20 hours of use my 850 burn 5 % per hour ( brightness 40%) and always on backlight.

At 40% brightness visibility is good even on sunny days..no need for more.

At the beginning, same settings burns 9% per hour….strange

Limiting to 40% is effectively using a battery save mode, and reduces the hero feature of the 850 (the screen) back down to the 840 screen level. 

I drop my 850 down to 60%, but I am seeing no downsides to the screen, because I used my 840 at 60% screen brightness as well. 

More importantly, you don't even need the backlight at all on the 840 due to the nature of the display. I always have the backlight set to turn off automatically after 15 seconds.

I honestly don't know. I've never been the type to monitor battery usage to be honest. I just get on and use it, and charge it when it gets down to around 20%.

It's bound to use more power due to the nicer screen, but it is what it is! I thoroughly like screen compared to the 840, so for me personally, it's worth the battery usage trade-off.