Spent a while googling, and can’t find an answer.

Does anyone have any idea of how long I could expect a Garmin 800 to last with the backlight constantly on at a low level?

I probably get about 13.5 hours out of one under normal usage.

I’d guess at less than.half that. Try it and let us know?

Wish I got 13hours.

It depends on your screen settings. Mine is now approaching 4 years old and the life is dropping off. Battery replacement by Garmin is very expensive though so I’m persevering as it works for the vast majority of my rides/

On the map screen with the light at 75% I get about 6 hours. When I drop it right down to 1 or 2 bars I get about 8-9 hours. I can get about 12 hours (1-2 bars) if I am on a simple data screen.

IF you want longer rides or reassurance then it runs fine when plugged into a USB battery. I’ve done this numerous times when having a map was essential or the ride was very long. I now use and Anker battery mounted under the stem using one of those cheap Velcro torch mounts. I run it off external battery first as I was told this is more reliable.

http://www.amazon.co.uk/Ultra-Compact-Lipstick-Sized-Portable-External-Technology/dp/B005QI1A8C/ref=sr_1_2?ie=UTF8&qid=1430379321&sr=8-2&keywords=anker

I’ve never run out of battery like this and have had it on medium brightness for 15h.

Yeah – I was kind of figuring I’d need an external battery.

With that battery, after 15 hours, is it still on external power?

13.5 hours was with the backlight mostly off, but switching screens occasionally and poking things and stuff. So probably not too far off what you get.

The battery on my Edge 705 was dying but I managed to get one online and there was a link to the battery change process. Nice an easy. Worth thinking about if you’ve a well used 800 I’d have thought.

Missus gets around 6-7 our of her 810 when in turn by turn mode so lots of screen usage.

Uses an Anker power pack in her pocket with a 1m usb cable plugged in. Has enough juice to charge it 2.5 times so will extend the battery by quite some way.