Sources of 12V power draw not backed by HVB?

[pnwadventures]

Similar to this recent (and as yet unanswered) post on the Model Y forum, I'd like to understand how to prevent draining my 12V battery even when the HVB has plenty SOC. For example, while car camping: exterior or interior lighting, stereo, USB accessories, 12V accessories (like a cooler, pump, etc).

I'm pretty sure that the AC compressor, cabin heater, and heated seats draw directly from the HVB, and that sentry/smart summon/main computer system draw from the 12V but keep the car "awake" so the 12V is tended by the HVB.

Are there any untended 12V draws in the car that I should be aware of?

 

[Frank99]

The "intended" operation of the 12V battery charging feature of the Model 3 is that anytime the 12V battery is discharged below a certain level (maybe 50%? I don't know), the HV contactor closes to power the charger until the 12V battery is fully charged, then the HV contactor opens. It doesn't matter if the 12V discharge occurs because an overhead light was left on, or because you were using the stereo to share your music with everyone in a half mile radius. As a result, it shouldn't matter what 12V power you use; the car should take care of itself and recharge the 12V as necessary.

I don't know what happens if you directly connect to the 12V battery to power, say, a refrigerator, and then let the car sleep. Perhaps the car wouldn't notice that the 12V battery was being discharged. Sounds like something you could test safely in your driveway. But using any of the car-provided 12V features (Cigarette lighter, lights/fans/audio, etc) should be safe.

 

[pnwadventures]

The "intended" operation of the 12V battery charging feature of the Model 3 is that anytime the 12V battery is discharged below a certain level (maybe 50%? I don't know), the HV contactor closes to power the charger until the 12V battery is fully charged, then the HV contactor opens. It doesn't matter if the 12V discharge occurs because an overhead light was left on, or because you were using the stereo to share your music with everyone in a half mile radius. As a result, it shouldn't matter what 12V power you use; the car should take care of itself and recharge the 12V as necessary.

I don't know what happens if you directly connect to the 12V battery to power, say, a refrigerator, and then let the car sleep. Perhaps the car wouldn't notice that the 12V battery was being discharged. Sounds like something you could test safely in your driveway. But using any of the car-provided 12V features (Cigarette lighter, lights/fans/audio, etc) should be safe.

That's good to know. We have another EV (Kia Soul EV) and it definitely does not tend the 12V when it's not "running", and I haven't been willing to deliberately try overdrawing the Tesla 12V as an experiment.

Also FWIW: I shouldn't have said "car camping" and "stereo" in the same sentence (or post), as that understandably conjures a stereotype (sorry for pun) that is 180° from me. I don't really "car camp", and never play music when I'm in the mountains/wilderness/etc. It's really annoying to play music in outdoor spaces where people go to escape. I don't even understand people wearing earbuds when hiking/skiing/climbing/etc.

I would however sleep in my car overnight, where legal, at a remote trailhead in order to get an alpine start for a big day in the mountains. I'd want to make sure that doing something like charging a camera, satellite messenger, etc. overnight (without having to leave climate control on) wouldn't result in a dead 12V in the morning.

 

[Big Earl]

That's good to know. We have another EV (Kia Soul EV) and it definitely does not tend the 12V when it's not "running", and I haven't been willing to deliberately try overdrawing the Tesla 12V as an experiment.

Also FWIW: I shouldn't have said "car camping" and "stereo" in the same sentence (or post), as that understandably conjures a stereotype (sorry for pun) that is 180° from me. I don't really "car camp", and never play music when I'm in the mountains/wilderness/etc. It's really annoying to play music in outdoor spaces where people go to escape. I don't even understand people wearing earbuds when hiking/skiing/climbing/etc.

I would however sleep in my car overnight, where legal, at a remote trailhead in order to get an alpine start for a big day in the mountains. I'd want to make sure that doing something like charging a camera, satellite messenger, etc. overnight (without having to leave climate control on) wouldn't result in a dead 12V in the morning.

If you aren't in the car and the car locks, the 12 volt systems like the power outlets will power down when the car goes to sleep (which can take some time). The car will monitor the 12 volt battery and charge it as necessary.

If you're camping in the car (sleeping at a trailhead, for example), you can enable camp mode to keep the car awake and the climate control on - this will keep the 12 volt systems powered up via the high voltage battery until the main pack state of charge drops below 20%. Dog mode and keep-climate-on modes function similarly.

If you're away from the vehicle (hiking, perhaps) but want to keep the 12 volt on without running the HVAC (for charging devices or powering a cooler), sentry mode will keep the car awake and the 12 volt systems active without wasting energy on climate control.