12V Questions

12V Questions

I am planning to do some car camping with the MX when it arrives. I would like to use a 12V powered refrigerator/freezer (ARB Fridge Freezer 37 Qt) while travelling. It draws an average of 1.35A (16.2W) so not a big impact to range. I am hoping to get answers to a few question to determine if this will be practical or not. (1) Is there a 12V power outlet in the rear of the car or is there only the one up front? (2) Does the 12V power outlet remain energized when the car is parked? I will switch to land power whenever it is available but there are many campsites without electricity. (3) Is the 12V power outlet sourced by the 12V battery circuit or is it derived from the high voltage battery inverter? (4) If sourced from the 12V battery, would pulling 1.35 amps for say 12 hours leave it unable to support power up of the car the next morning? Thanks to anyone who can help with these questions.

darlin | 18 mei 2016

The Main battery charges the 12V battery which supplies the power outlet and other 12 accessories(lamps, dash etc). The 12V battery does not directly start the car, but when it goes dead the doors may not open as they are powered by the 12V system. 12 hours may put quite a dent in the main battery as it powers the 12V.

rossRallen | 18 mei 2016

@c3 - I suggest you contact Tesla Technical support, and share your experience.

I don't know the circumstances under which the Main Battery recharges the 12V (actually probably 13.6V) system, but 1.35 A x 13.6 V x 12 hours = 0.22 kw-hr is about 0.6 mile of range. Now, if sourced only by the 12V system, that might be a problem. If the Main Battery is recharging the 12 V system during that time, then it's almost invisible.

Dcp9142 | 18 mei 2016

When the 12 volt battery is dead, the car is dead. Modern electric cars will not boot without 12 volt power to energize the contact or for the traction battery. This is true for hybrids and pure electrics. With 12 volt dead you must access the frunk manually through the towing eye hatch, open frunk, and jump a 12 volt source to the jumper terminals. With anything but a Tesla, you just use a mechanical key to access the car, open the hood or trunk, and attach the 12 volt source. Elon made recovering from this failure mode complicated in order to avoid a mechanical lock.

rossRallen | 18 mei 2016

Dear Tesla: give drivers info on the state of charge of the 12v battery.

c3 | 18 mei 2016

Thanks for the helpful info thus far. Still looking for answers to at least questions (1) and (2) however.

darlin | 18 mei 2016

You need an actually owner for those questions. I have not picked mine up yet, sorry.

lilbean | 18 mei 2016

1. No outlet in the rear.
2. Yes, is powered when in P and when car is on. If there is prolonged inactivity in P, then the car powers off.

Gary an Rachel | 18 mei 2016

Yes, 12volt outlet in very back in trunk area. It has a flip cover on it. I use it for vacuum.

lilbean | 18 mei 2016

@garyandrachel: thank you!

c3 | 18 mei 2016

@lilbean Good news on outlet in back. Not so good news on auto-power down. Thanks for the info. It would be soooooo nice to tap into that huge battery for camping needs but it sounds like I may need to find a different solution.

oragne lovre | 18 mei 2016

@Gary an Rachel,

What kind of vacuum do you use that is compatible with the 12-vold outlet? I'm shopping for a small vacuum for my X.

ir | 18 mei 2016

Put car in N and engage E-Brake and the car should stay on. I suggest you invest in some wheel choks if that makes you nervous.

Gary an Rachel | 18 mei 2016

oragne lovre, hmm it's like a dustbuster in shape but is sold for cars and 12v cigarette lighter plug. I'm not sure who made it. My wife thinks it came with her Lincoln Navigator. I think she is correct. I use it in our X and the plug always seems to have power. It's never failed yet due to power. So I'm not doing anything special to keep power to socket. Hope this helps you. Plus I have a retractable feather duster to do dash area and such.

Triggerplz | 18 mei 2016

@ Orange lovre I have a cordless Black and Decker 9.6 DustBuster vacuum that hangs on the garage wall and charges it works very well it even has an extender on the end u can pull out

Gary an Rachel | 18 mei 2016

I just checked the power level at the rear 12v plug. It's holding solid at 14v and this must be the reason my plug in vac is working so well. I think for little frig will work great and maybe create ice cubes at 14v. Grin.

Triggerplz | 18 mei 2016

@gary an Rachell I had one of those little frigs it never really got cold, my old 2005 Lexus LS430 had a frig in the rear armrest it kept sodas and water cold..

Blue85DCalifornia | 18 mei 2016

>> 3) Is the 12V power outlet sourced by the 12V battery circuit or is it derived from the high voltage battery inverter? (4) If sourced from the 12V battery, would pulling 1.35 amps for say 12 hours leave it unable to support power up of the car the next morning?

Yes, it comes from the 12V battery. No, you can't run it down - when the 12V battery gets to about 50%, the high voltage battery contactors engage, and the high voltage to 12V inverter charges up the 12V battery. This is the source of "vampire drain" - it's the high voltage battery having to engage every now and then to recharge the 12V battery because the 12V battery is constantly being drained by the electronics, some of which never turn off.

Your fridge won't prevent the X from starting by running overnight unless your high voltage battery is so dead that it can't recharge the 12V battery as needed. Clearly your average 16W fridge (even with inverter and charger inefficiencies) will have minimal effect on the 90,000 watt Hr high voltage battery pack.

I have no idea if the 12v socket in the rear is full time. In the S, the front 12V socket turns off some time after the car shuts down. It is not full time. On an S, some folks use the constant 12V power from the ODB-II connector in the front driver wheel well. On the S, that only has a 5A fuse, so it will not power a fridge (the 1.35A number is average - not peak.)

r.hauser | 18 mei 2016

From the owner's mauual:
Your Model X has a power socket located on
the front of the center console. An additional
12V power socket is located in the rear trunk.
Power is available whenever the instrument
panel and touchscreen are on.

The 12V power sockets are suitable for
accessories requiring up to 11A continuous
draw (15A peak) or a maximum of 150
continuous watts (180 watts peak).

So plenty of power to connect your fridge but not continuous. When car goes to sleep so does your fridge. LOL

c3 | 19 mei 2016

@ Blue85DCalifornia Thank you very much. This is exactly what I needed to know and suggests that I will be able to travel with a fridge for car camping.

@ r.hauser This confirms that I will need to tap 12V power at the ODB connector per suggestion from Blue. A little less elegant than the power outlets but it should work.

@Triggerplz You may be thinking about what are sometimes called electric coolers. They work on a different principle than a true compressor based refrigerator and can only maintain a differential temp from ambient. The type I am considering work extremely well and are often found on boats and RVs.

I had originally planned to tow a small Airstream behind the MX which it is more than capable of doing (with an expected reduction in range). Unfortunately, I have concluded that it is simply not practical for trips of any distance since you have to hitch and unhitch the trailer at every SuperCharger which would get tiresome very quickly. Thanks to all for the information. My MX camping dreams remain alive.

Triggerplz | 19 mei 2016

@C3 yea thats what I was thinking, my bad

darlin | 19 mei 2016

A useful forum topic with great information. Thanks all.

eric.zucker | 19 mei 2016

Would the 12V outlets stay energized while the car is plugged in / charging ?

c3 | 19 mei 2016

@eric From what others have said thus far, I suspect it will power down whether plugged in or not but I am just speculating/extrapolating. Perhaps someone can confirm. For my application I need to draw 12V power while off the grid although I can imagine others who will need it while charging. My solution will be to take power from the ODB connector and replace the 5A fuse that powers it with a 15A fuse. My fridge draws 1.35A on average but they recommend a 15A fuse to handle peak current.

lilbean | 19 mei 2016

I tried powering it up while charged and it wouldn't. I tried plugging in my pump and it wasn't drawing power from the vehicle. I then unplugged and powered up the car so I could use the pump but then the car powered off when I opeend the door. I power it up again by pressing on the brake and then it powers off when I open the door. I couldn't power up the car with the door open. I suppose I could put it in neutral but I didn't want to take the chance on having the car roll.

c3 | 20 mei 2016

@lilbean Thanks for sharing your findings. Much appreciated.

Blue85DCalifornia | 20 mei 2016

@c3 "Blue85DCalifornia Thank you very much. This is exactly what I needed to know and suggests that I will be able to travel with a fridge for car camping"

I have a Dometic CF-35 that has been across the country in my S and multiple camping trips. Increasing the ODB-II fuse size from 5A can be unsafe as the wiring and ODB-II connector may be damaged or worse by drawing more power than designed.

A better solution for me was to locate the relay under the hood that switches power to the 12V port. I unplugged the relay and used a 2 inch piece of wire with spade lugs on each end to plug into two of the 5 holes for the relay. This provides continuous 12v power to the 12v socket. Works great. Fridge stays on all the time.

FYI, there is something informally called camper mode that also leaves the 12 V socket (and possibly much more) on all the time. It does not work while the charger port is occupied. Shift to nuetral, use the center screen to set the parking brake. Turn off daytime running lights. Turn off HVAC (although some use this mode precisely to keep the A/C running for a pet. Or themselves if sleeping inside). Dim the screen brightness. My car uses less than 7mph left overnight ON with no HVAC. I used this to keep my fridge running while camping at Zion National park two nights until I read on another forum website about the relay that controls the 12v socket.

lilbean | 20 mei 2016

C3, you're welcome. Today the car stayed powered even after I opened the door while I was in park after driving. I think it wouldn't stay powered on because it wad parked in the garage and I was trying to keep it powered without driving it.

lilbean | 20 mei 2016


c3 | 21 mei 2016

@Blue You have obviously paved the way for those of us interested in car camping and I really appreciate the tips. There is little doubt that the MX will also have a 12V power relay (perhaps in a different location) and I think shunting that is the best solution I have heard yet. The MX may offer additional options as well given the towing harness and brake controller provisions both of which have 12V terminals present. My car is scheduled to arrive at the SC next week so with any luck I should have it soon. Once in hand it will be a lot easier to sort all this out and I will share what I learn.

I also like knowing about the "camper mode" option. While I prefer to sleep in a tent when car camping, I like the option of sleeping in the car on occasions when the rain or snow is really coming down. I purchased a 6-seater specifically to allow for this. I plan to build a center console that is flush with the folded 3rd row seats to support my legs. "Camper mode" opens up the possibility of also ditching into the car when outside temperatures are really high (I enjoy sleeping outdoors in cold weather with the right shelter and sleeping bag/pad - I absolutely hate sleeping outdoors in high temp/humidity environments). I'll need to determine how much energy is consumed by running the HVAC all night at various outside temperatures to see if this is feasible. My guess is that it is.

WarrenJason | 15 oktober 2016

This thread has been incredibly useful to me. I also have an ARB trucker's refrigerator that I take with me on almost all my road trips, albeit an 64 quart one.
I found this video when I looked up "camper mode":
On my brand-new Model X 90D, I've had very mixed results with the rear 12V outlet. Prior to downloading rev 8.0 of the software last week, the rear and front outlet power seemed to turn on and off with no pattern I could fully identify. At one point, there was absolutely no way I could keep the power to the fridge constant.
Subsequent to the version 8.0 update, I now note that the power to the rear 12V outlet never seems to turn off.
Right now, I'm still scratching my head and trying to figure all of this out.
I just canceled a service call upon discovering that the model 8.0 update seemed to make this change.
Any additional clarification would be much appreciated!

Waldek | 22 april 2017

@WarrenJason it seems like they changed it again in some update as both lighter outlets on 8.1 17.14.35 build goes off when car turns off... :( I wish there would be a way to just keep it on by some settings switch

sven | 20 juni 2017

@c3: "My car is scheduled to arrive at the SC next week so with any luck I should have it soon. Once in hand it will be a lot easier to sort all this out and I will share what I learn."

So c3 - after over 1 year - what have you learned?

DaddyP713 | 21 juni 2017

I'm interested as well. We're about to go on a long road trip with some car camping... | 21 juni 2017

Words of, advice: Never, as in at no time, put a higher amperage fuse in place of a lower amperage fuse. Carrying some spare fuses in the car would be a good idea.

I'm thinking it may be easier than you think to use the fridge. Plug it in while driving to cool it down and keep it there. If 12 volt outlet turns off overnight, a well-insulated fridge will probably not warm up more than a few degrees.