How and when does the 12v battery get charged?

[NathanielHrnblwr]

I bought one of these:

https://www.costco.com/Michelin-12-...Warmer-with-AC-Adapter.product.100477869.html

The manual states to not use it for more than 4 hours from a 12v source to avoid draining the battery. I'm curious how this applies to the Model 3. Will the HV battery charge the 12v as needed? Not that I plan on leaving this running in the car for 8 hours, but don't want to run down the 12v either and worry about nearing 4 hours of use if at the zoo or something.

 

[mongo]

The car will top off the 12V battery as needed. I'm not sure if the current software leaves the power ports in the cabin on while the car is off though. Worst case, you might be able to use dog mode (or app based preconditioning) to keep the car on-ish.

 

[Rocky_H]

The manual states to not use it for more than 4 hours from a 12v source to avoid draining the battery. I'm curious how this applies to the Model 3. Will the HV battery charge the 12v as needed? Not that I plan on leaving this running in the car for 8 hours, but don't want to run down the 12v either and worry about nearing 4 hours of use if at the zoo or something.

Well, I have good news, and I have bad news:

1) That warning is irrelevant for battery electric cars. The warning would apply to gas cars, because they can't/won't start themselves back up to run the engine to drive the alternator to recharge the 12V battery. They just don't monitor that when they're off. A Tesla car would be fine with that. It constantly keeps and eye on the 12V battery very much because it does have some levels of computer drain on it while the car is sitting, so it does have to refill the 12V from the main pack from time to time. So yeah, you hypothetically could leave it in there running for weeks without draining things down much.

The bad news;
2) I don't really know if that would work. I think the Model 3 is like the S and X, that it shuts off the connection to that cigarette lighter 12V socket when the car is off. So you would probably have to hack something together to keep power running to that socket when you are away and the car is off. Maybe some of the "keep climate on" or "cabin overheat protection" settings also serve to keep that 12V socket active too?

 

[Rocky_H]

Oh! I did just remember the other hack-ish workaround to make sure to keep the car officially "ON". I did this specifically for the purpose of charging up a friend's phone in my car from that 12V socket while we got food and he would be going back to his car to leave, where he didn't have a charging cable.

Press the door almost closed until you get a little first click, but it's not fully slammed shut. When you walk away, the locks will engage, so the door can't be opened by the handle, but the car won't detect the door as being fully closed, so it stays on and won't shut off.

That kind of thing will work on most cars. At least that works on the Model S. I would think the 3 probably does too.

 

[NathanielHrnblwr]

OK thanks for the replies. I wanted to make sure the 12v wasn't only charged when the HV battery was at a certain level or above or when the car had external power. I'll mess around with the 12v. Dog mode or maybe even sentry may keep it on.

 

[darth_vad3r]

OK thanks for the replies. I wanted to make sure the 12v wasn't only charged when the HV battery was at a certain level or above or when the car had external power. I'll mess around with the 12v. Dog mode or maybe even sentry may keep it on.

As long as you have enough battery, I'd go with "keep climate on" as my first approach, since keeping the cabin cool will help keep the cooler... err.. cooler

Remember these types of coolers only cool a certain amount below ambient temp. That one specifically says:

• Cools up to 40F (20 C) below surrounding temperature without any ice

So if you don't use "keep climate on" (or dog mode) and the car heats up to 40C, the "cooler" will do it's best to keep things at room temperature ... probably not what you want. Instead if you use "keep climate on" to keep the cabin at say a more reasonable, not-too-warm 22C, you can expect the cooler to possibly keep things as cool as 2C above freezing.

I've been meaning to test this out myself actually. We've had one of those type of coolers for a few years and they come in handy on long road trips. It would have been nice to have a 12V outlet in the trunk too like we have in our gas guzzling SUV, but those definitely don't stay on when the car is off in a non-EV (at least not normally I don't think) and if they did you'd come back to a dead battery after a stop, so not a great idea.

IMO, climate control always being able to be turned on even when the car is "off" is one of the greatest features of EVs (I think they can all (mostly?) do this, not just Tesla).

Anyways, if you test it out (the status of the 12V outlet power under various scenarios) please report back! Thanks.

 

[darth_vad3r]

Found this in the manual, on page 21 (page 23 of the PDF):

12V Power Socket
Your Model 3 has a power socket located in the center console's rear compartment. Power is available whenever the touchscreen is powered on. The power socket is suitable for accessories requiring up to 12A continuous draw (16A peak).
​

https://www.tesla.com/sites/default/files/model_3_owners_manual_north_america_en.pdf#page=23

I guess if that's strictly accurate, Dog Mode would help, but who knows ... that might not qualify as the touchscreen actually being 'on'? Will definitely need to test this out

 

[darth_vad3r]

I did a super quick test (1 minute only) and the 12V outlet stayed powered (as indicated by a blue LED on a 12V adapter I have that I plugged in without actually putting any load on it) for both of these scenarios:

1. Leaving car in park, exiting and locking doors behind me
2. Staying in car and manually choosing “power off” from the touchscreen safety menu

Didn’t have time to try a longer test but looked promising after 1 minute for each test the blue LED was still lit

2019 Model 3 SR+ running 2019.12.1.1

 

[mongo]

I did a super quick test (1 minute only) and the 12V outlet stayed powered (as indicated by a blue LED on a 12V adapter I have that I plugged in without actually putting any load on it) for both of these scenarios:

1. Leaving car in park, exiting and locking doors behind me
2. Staying in car and manually choosing “power off” from the touchscreen safety menu

Didn’t have time to try a longer test but looked promising after 1 minute for each test the blue LED was still lit

2019 Model 3 SR+ running 2019.12.1.1

Blue LED? I thought yours was red.

 

[darth_vad3r]

Blue LED? I thought yours was red.

Are you confusing LEDs with lightsabers?

So I did a bit of a longer test today. Car was parked and locked for 1h12m between uses and the blue LED plugged into the 12V was on for all of the 3-4 times I checked, which included a few during the first 5 minutes and one last one before using the car again (before unlocking car, and without the key anywhere near the car).

Sentry was off, but Cabin Overheat Protection was on, and the fan had kicked in by the end of the test, so it’s still possible the power got cut at some point and came back on when the fan kicked in, but I still consider this a pretty good test result for the cooler usecase anyways. I’d expect to actually go beyond using just C.O.P. and use Keep Climate On so that the 12V cooler could have a chance to maintain near-freezing temps since it can only cool to a max of -20°C below ambient temp.


[DUT: 2019 Model 3 SR+ running 2019.12.1.2]

 

[darth_vad3r]

Oh, so I did a followup test. I used Find my iPhone to try and check remotely if the USB and 12V outlet were powered or not based on if the two devices I left in the car plugged in charging in those 2 outlets (front driver's side USB and 12V outlet) showed 'charging' or not from a 3rd device in the Find my iPhone app.

I didn't get super-conclusive results because I think once devices get fully charged they stop showing the lightning bolt icon

I was able to deterimine (this was still on 2019.12.x before getting 2019.16) that the power to both front driver's side USB and the 12V power outlet seemed to cut out after 10-11 minutes (presumable car went to sleep).

I was also able to determine that turning climate control on from the app restored power to both.

Also the remotely turned on climate control turned itself off after 4 hours (I got a notification saying as much). Unlike the in car "Keep Climate On" which purportedly stays on 'forever' (until battery gets to 20%).

So anyways, if you are using a cooler in a 12V outlet, and you are keeping the cabin cool as well (so that the cooler will actually work), you should be fine having power to the 12V the whole time.

Eventually we'll get "Party Mode" in addition to Dog Mode so that sounds like it will be a way to keep things on possibly without having to rely on other settings.

 

[israndy]

My tests have been totally screwed up by Sentry mode coming on. Every time I see the camera still going I discover that sentry mode has come on despite my SPECIFICALLY turning it off AFTER I parked (I think). So a few more days of testing. Finally figured out how to disable Sentry at my house, and I am now trying to remember to check each time I record the range to check if Sentry is off. We'll see.

I do think it's possible that if you have something plugged in that the car stays awake, but I am still testing. The downside of getting an odd update in the middle of testing. Anyone else get 15.11?

 

[darth_vad3r]

All my tests were done with Sentry Mode off. I assumed that if it stays on, and the computer/cameras are on, then everything else might stay on so I didn't bother testing with it on at all yet.

Also I haven't done any tests with 2019.16 when they changed the Sentry Mode menu to allow it to always be on. I think with 2019.16 if you turn Sentry Mode "on" in the menus, it always stays on unless you add an exclusion. Not sure if tapping the Sentry Mode icon in the tray does the same thing as turning it on in the menu, but that's the only way I've used it since 2019.16 is with the tray icon and I've turned it off manually afterwards each time since I'm not interested in it defaulting to on all the time right now

Anyways, I think we'll be set once "Party Mode" gets added to Keep Climate On and Dog Mode, as Elon tweeted about recently.

 

[Rottenapplr]

I was surprised to learn the tesla even has a 12v battery. You would think the large battery pack is enough.

 

[mongo]

I was surprised to learn the tesla even has a 12v battery. You would think the large battery pack is enough.

Vehicle systems (displays, lights, power steering) run on 12V. The 12V is also used to activate the main contactors in the pack which allows the high voltage to run the big stuff.

The Y may do away with the 12V battery entirely.

 

[NathanielHrnblwr]

So far this cooler has worked well. It does indeed stay on when I leave the car. It came in handy when I bought some perishables and decided to top off the car at the SC on the way home.

 

[darth_vad3r]

So far this cooler has worked well. It does indeed stay on when I leave the car. It came in handy when I bought some perishables and decided to top off the car at the SC on the way home.

Did you use Sentry mode or Keep Climate on to stop the car from going to sleep?

My tests with the 12V outlet with 2019.12 showed the power cut out after ~10 minutes unless I did something to stop the car from sleeping.

 

[NathanielHrnblwr]

I have sentry mode on now, but when I tested it I did not. I was not aware of the 10min threshold though. I just locked the car and saw the LED of the cooler on. Good to know, thanks.

 

[darth_vad3r]

Spotted "new" wording (dated May 16) in the manual:

Note: Power is available whenever the vehicle is considered "awake" The vehicle may be awake for many reasons. For example, when using features such as Summon, or when features such as Cabin Overheat Protection, Keep Climate On, Dog Mode, Sentry Mode, etc. are enabled. The vehicle is also awake whenever the 12V battery is being charged or is in use, during HV charging, when the vehicle is communicating with the mobile app, etc. Leaving an accessory plugged in does not deplete the 12V battery.
​

Source: May 16, 2019 dated PDF manual, page 22 (pdf page 33):
https://www.tesla.com/sites/default/files/model_3_owners_manual_north_america_en.pdf#page=23

Kinda funny actually, my last quote of the manual in this thread was on May 16, but the wording on that date was different ... so not sure when this May 16 dated manual actually got published

 

[Itsuo-DC]

Any updates on this?

I plan to head out this weekend to go car-camping with a powered cooler/freezer. It has built in “battery protection” which I plan to use in the lowest setting in hopes the the DC-DC Charger will top of the car’s AGM before the cooler shuts off...

GO Series

I will probably use the 12v extension cable it comes with to keep the cooler powered and outside of the vehicle during the day (where I assume it will be more temperate).

I always keep the cabin overheat protection on so based on this thread I hope that’s enough to keep the 12v outlet on continuously. I would guess the cooler uses no more than ~30Wh between the compressor cycling on/off.