I have a new Varia that I’ve been using for a few rides this season.
What sort of battery loss on your head unit are others seeing?
I have a Garmin 520 that, while paired with the Varia, can barely make it four hours. It’s getting old but the battery drain from using the Varia is quite drastic.
Also… Does anyone have trouble keeping it connected to the phone app? I’ve used it a handful of times but it won’t stay connected to the app for longer than 30 minutes.
I have a 510 and 530. I never noticed that using the Varia radar drains the battery any more than when not using it. Maybe your 520 battery has gotten weak and needs replacing? I rode 1.5 hours the day before and 2.5 hours yesterday and my 530 was only down to 80%.
I have a Wahoo Bolt and same: i do not see any significant additional battery drain at all.
I had experienced significant head unit battery life loss from the Varia. So much so that I got rid of my 520Plus and got the 530 for the extra life.
Then discovered it was due to my backlight settings. Turn the backlight timeout to the minimum setting - uses far less power with each Alert from the Varia.
You mean backlight of the Garmin headunit? Why would it use additional energy by the Varia? I dont know how the Garmin headunits work, just curious.
I ride with the bolt with backlight off. The B/W screen is perfectly readable, no backlight needed.
I think it uses some energy dependent on the numbers of sensors the head unit is reading a signal from but for me its not noticeable. I think the early guides was to switch all the sensors off to maximise battery life but with modern batteries its insignificant.
Edit: I should have read the post above yours, I guess the varia for him was constantly triggering the backlight to come on. Not an issue fortunately for me 
I think the backlight was lighting up with each Varia alert (just not noticeable in daylight), and with a 2 minute timeout, that was a significant amount of backlight uptime in traffic.
The Garmin screen is perfectly readable with no backlight as well.
Anyway, cutting backlight timeout to the minimum has significantly reduced battery consumption. I could turn the BL off completely, but I tend to get lazy and just leave it on Auto for low light conditions.
mcalista is correct. I have an OG varia, and with my 810 default settings, the light comes on for 30 seconds for every alert. It hits the battery hard enough that for long rides (4+ hours) I turn off the light altogether.
-Tim
I did the same - upgraded to the 530 for more battery life. Even with backlight set low I could only get about 6 hours out of my 520 Plus when running navigation, Varia and phone connection. I went on a 100 mile ride and had 1% battery when I got home…
With the 530 I went on a 7 hour gravel ride last week with navigation, Varia and phone and had 67% battery left.