2020 ES300h Auxiliary Battery Outage

[nyuhsuk]

Ran into a battery drainage issue this past weekend.  Drove my ES300h on Sunday morning and then on Monday morning, car's battery was dead and the car would not start. Symptoms included flickering lights, clicking noises, and an intermittent warning message on the display stating roughly 'Elec Access System Malfunction'.  Was not sure if this was a battery issue as this is my first foray into hybrids.  After Roadside Assistance came and jumped the car (I was told by Lexus not to do this myself - which I probably will just do next time), 'Check Engine' lights remained and I decided to take it in to make sure nothing was wrong.  After a lengthy wait at the dealership, it was decided the auxiliary battery was completely drained and needed a full recharge.  Battery diagnostics came back fine.  Not sure on their end why the battery died.  Car was purchased new in September 2020.  Supposedly one of their most reliable and durable batteries, being a higher end gel model.  Has anyone experienced this in their hybrid?

A couple of notes:

- Use a sunscreen on the windshield so I prop it up with my visors.  One thing different this weekend as opposed to others is the fact that the mirror was left open but once the visor is fully extended, the mirror light turns off.  Even if the light was on, would it drain it in a day?  Or is leaving the visor open in general, mirror open or not, slowly draining the battery?
- I have a dashcam (A119v3 - capacitor powered) and a phone charger plugged into the center console DC port.  This should disconnect completely once the engine is cutoff no?
- No other interior lights were on.
- All car doors and windows were closed - both the car locks successfully and the app did not notify me of any status otherwise.

[RX400h]

Some vehicles' 12V ports are live even after the the vehicle is shut off. Is there an "ON" light on your phone display that you can check when it is plugged in after the car is off? Auto Electric shops can track down electrical current draws if the dealership cannot, but I think it is highly unlikely that a failed component is causing the drain.

How many days apart do you drive the ES? Simply waiting too long between sufficiently long trips can result in a dead battery. We drive our RX400h at least once per week and for a minimum of 12 miles, one way. Our battery always starts the car without issue.

[nyuhsuk]

The dashcam shuts off about a second or so after turning the car off (since the capacitor needs to drain) and the phone disconnects immediately so AFAIK, that is working as expected.  I have not done more sophisticated power readings as this seems to be proof enough that the power shuts off.

I drive 5 days a week, 45 miles minimum daily (~22 each way to work).  And more often than not a day or so on the weekend and trips are nearly never under 5 miles each way.  That was never an issue of concern either.

Stumped as it sounds like a bug.  I was thinking about taking battery health readings every day to see if it's something else (visor open w/mirror closed to prop up the sunshade).

On a side note, does anyone have documentation stating exactly what scenarios charge the auxiliary battery?  I was told the car being on but not running does not charge the auxiliary battery since no alternator exists.