So, I have been monitoring the 12 V sub-system from the system-power bus, after recently charging it with an external charger to FULL - and I find that the car's system bus voltage is still showing 12.3 V as the resting voltage. I'm measuring from the system bus voltage that powers the rear-view camera's power. It never goes below 12.2 V so long I don't go into ACC mode.

I'm coming around to believing that the design of the 12V power subsystem is designed to be lower than usual (usual being historical ICE convention) for Toyota/Lexus hybrids - since the 12 V battery even when fully charged is regulated to 12.3 V for the system bus. In other words, I don't consider the resting bus/battery voltage as 12.3 V being abnormal or risking battery death.

Given the $100 ES that is attached to my 12 V battery (for insurance), I don't consider the 12 V battery to be a problem with the car anymore - a 12 V battery death (which hasn't happened in over 1 year for me) simply isn't a problem anymore. I stay out of ACC mode as good hygiene.

One more thing: Although I can't prove it - I don't believe Lexus/Toyota's software updates are sophisticated enough to update the firmware of the car. Software updates are only for updating the Nav/MID system, not deeper functionalities. So I don't hold any hope that OTA "software updates" can/will ever change the charging algorithm.

 

"No problems — Until today,16000 km! as long as no mechanics have touched your vehicle and put it back together wrong. :-)
So far, it was all just rumors and fears about new technology