Varia battery status in %

agree completely. Sensor battery info could be much better. I’ve nearly lost gears twice on rides as di2 info is so limited. It was briefly changed to % but with 12 speed it’s back to 4 bars again. 
the sensor summary after a ride would be much more useful if something other than OK was given. It’s not really that helpful. 

yes it is. Look for datafield for that - same for battery level of DI2 

So its inconsistent. I have the same light as you and it appears twice in the sensor list, as a light and as a radar.

Under the radar info I see what you see

Under the light network I see a battery level

But if I go into the sensor details under the light I don't see a battery level and it doesn't look up the manufacturer

I also noticed that while the di2 battery level has 5 bars, the low battery warning that comes at 20% battery, corresponds to 2 bars on the display which should be 40%. Di2 battery only reports in 10% increments so possibly they're mapping the single bar to <20% and 2 bars to <40% instead of <=20% and <=40%.

For Sensor batteries there is no display in %.

There are only 5 states or bars, which stand for:

-New (even for rechargeable batteries)
-Good
-OK
-Low
-Critical

Thats useful to know, thanks. A percent figure would be much more useful though, where available (like on di2), as without your reply I would have had no clue what those levels actually mean, and I suspect 99% of people wouldn't either. Otherwise if they fixed the mapping of di2 that would be a start, so 2 bars is 40% not 20%. Twice I've been caught out by di2 low battery warnings when I thought it was much higher.

Just checked the sensor list in GCM and I'm also seeing "Full" for di2, not "New"

I found the table of what Garmin map di2 battery levels to at the link below (table included), contrary to what you would expect, 2 bars isn't 20%-40%, its 11% to 25%, so its not a linear scale. Not a great design decision in my opinion

https://support.garmin.com/en-GB/?faq=qBnD0bXiLT7g6qMyExVRc9

OK - 50% and 26% is a massive difference for Varia. I had it OK and it died during the ride((

That scale is for Di2, but I'd guess they do the same for other sensors. For di2, as it only reports in 10% increments the battery is actually 20% when you get down to 2 bars and get the low battery warning. By then, based on Shimano stats you only have 100km to go before the unit starts restricting shifts. From the number of bars you'd expect 40% and 300km left. Thats based on Shimano estimating 1000km from a full charge for 12 speed di2, and will obviously vary based on how many times you change gear.

Did some digging, expanding on what mcinner1 said, the battery level is a common item baked into the ant+ spec as New, Good, OK, Low or Critical. There is no option to send a battery percentage there for the Varia. It would as far as I can see need an update to the ANT+ specification.

What you can do though is pair the 515 to a phone via bluetooth, I think the bluetooth protocol supports a percentage, although the app has a battery icon, it should at least give you a more granular view.

1000km from a full charge is very pessimistic.  I’ll easily get at least double that. I think they take worst case where someone needs a lot of front shifting which is the biggest drain.  While I do ride the hills a fair amount (7500+m a month) I also spend a lot of time on rides where only rear shifts happen. Anyone not living in a hilly environment I’d say this is reality.  

I think the scale like that (non linear) is not a bad way to do it. With a reasonably good battery (in terms of age) 26% would give me a good 200km or more. Enough that if it came up during a ride I’d get back and just have to remember to charge. Most people get a flat battery because they don’t have a head unit telling them, don’t have the Bluetooth dongle and they can’t see the LED warnings on the charge port (11 speed version).  12 speed - no excuse as Bluetooth is now built in,

As for other units like lights and radar, since their battery life isn’t much over 10 hours.  25% is really getting low and doesn’t give a lot of ride time.