Are you saying you can’t get target power in a custom screen on the 840?
I have a 530 and just followed this guide and find it works perfectly well.
https://support.trainerroad.com/hc/en-us/articles/360028380691-Creating-a-Custom-Garmin-Screen
Also, the way TR send workouts with ‘lap button to end’ rest between interval sets (actually it’s an additional rest interval with duration being till lap is pressed) is very helpful, and am not sure if Wahoo supports that. There may be an easy Wahoo workaround though e.g. pausing the whole workout (which hopefully doesn’t pause the ride).
Only other comment for the OP is that you don’t (or probably shouldn’t) spend a lot of time looking at the screen during a hard workout, so really only need basic info in my experience. You will get used to what tempo, sweet spot, threshold, vo2 etc feel like so can target power without looking at the screen often. And the outdoor workouts in general are less complex than indoor so targets are easier to keep track of.
Pausing a workout on wahoo does not pause the ride. Ride is still recording but it pauses the current interval. I try to save that for recovery intervals when possible.
I added the workout fields to BigScreen, though I haven’t released it to the ConnectIQ store yet (need to do some more testing first).
Here’s a representative screen captured from the ConnectIQ simulator (though the target data is bogus). “INT TIME” counts down to 0, and then the “NEXT” data moves into the “INT” data. I think it’s useful to see the next interval so that you know what’s coming up. The Garmin APIs don’t expose the whole workout.
And here’s a ridiculously detailed screen that adds every metric displayed by the TrainerRoad desktop app:
Color coding is used for power and HR zones, and can be fully configured.
Got out for a one hour zone 2 the other day and I used about 10% over an hour so it’s in line with the 10 hours you are reporting. I have a power meter, heart rate sensor, radar and Di2 connected as well as paired to my phone for live tracking. Screen is set to Auto Max. As I said before, I don’t do rides that long but it does seem pretty low battery life. I only got it over the winter and that was my first ride with it so can’t comment on whether a recent firmware update made it worse or not but I can confirm that it’s not just yours.
yeah it seems like it is a firmware issue and they’re working on it
Don’t know if the issue has been fixed or not but I went out yesterday with same sensors and settings for the same amount of time and only had 2% battery drop. Might be different lighting requiring different amounts of backlight perhaps.
If anyone’s interested, I added 10 workout-specific datafields to BigScreen this week.
