My 17 Volt has a 175 amp DC-DC converter that charges the 12v battery from the traction battery. It's interesting that this converter is cooled via the same liquid cooling loop that cools the traction battery.
I have a 4kw inverter connected to it and have used it several times to power large loads for several days in my home during power outages, including refrigerators, lights, TV/Computers, vacuum cleaners, and also the furnace(as the guy in the article has).
I have been doing this since I bought the car in 2018 and the only ill effects are when I forget to turn it off(when the vehicle is off) and it drains the 12v battery. I've done this (drained the 12v battery accidentally) about 20 times so far and it has not noticeably impacted the 12v battery.
I also would not expect any warranty support for this charging system and battery as I am clearly using it outside its intended purpose.
From linked article:
> Through the low voltage architecture, you can get the power from the main battery pack and power several devices on the inverter.
I don't know how Tesla is wired but this article suggests that 12V lead acid battery is constantly charged from primary lithium battery. It sounds like hooking up electrical load to main battery but with extra steps.