[Joeyl328]

Tons of Model 3's any Y's coming in for a $1400 repair due to 12v taps in the wrong place.

I am in no way telling anyone what to do. Do whatever you want, however tapping 12V under the rear seat is easy, but potentially dangerous as far as the wallet is concerned.

VC front protects the PCS from 12v shorts and high current situations with ultra fast mosfet switching. I created a super simple generic picture from a VC front that I have.

12V gets created in PCS and is then connected to VCfront (right behind the 12V battery). VCfront then feeds everything else - including VCright and VCleft and the 12V battery under the hood.

View attachment 40474
You will certainly find 12V under the rear seat and people are tapping there and then something gets shorted out or some kind of high current occurs with the tap. The only protection from a tap under the seat are fuses under the penthouse that are EXTREMELY slow to blow and expensive to replace - ultimately voiding the warranty.

1. 12V is created under the penthouse.
2. PCS feeds VCfront its 12V.
3. VCfront divvy's up 12V around the entire vehicle including the 12V accessory battery.
4. VCfront monitors the current flow that is passing through the high power mosfets using the shunts.
5. If the shunts detect a short or illegal current flow the CPU on VCfront can open the mosfets in microseconds to protect itself and PCS and the other VC's from any damage..

The PCS's 12V ( under the rear seat) IS NOT the same as the 12V battery positive lead.

WARNING: The same holds true to the NEGATIVE mosfets ( not shown ) on VCfront. Chassis ground IS NOT the 12V batteries ground. They are separate.
WARNING: Don't weld anything on the vehicle if the chassis ground has been shorted to 12V battery ground through a 3rd party accessory. If you do....kiss your PCS goodbye and get your wallet out. Warranty voided.

Thank you for this info. So would safest bet for a amp and subwoofer (not a super powered one) be to connect positive and negative from battery in frunk?

 

[modifications]

Thank you for this info. So would safest bet for a amp and subwoofer (not a super powered one) be to connect positive and negative from battery in frunk?

Yes. Absolutely.

 

[eXntrc]

Out of curiosity, what is the highest amperage that can be pulled from the positive terminal in the frunk without tripping protection in VCFront?

 

[JWardell]

Out of curiosity, what is the highest amperage that can be pulled from the positive terminal in the frunk without tripping protection in VCFront?

Well the output signal goes up to 400A but really only one way to know for sure...

 

[modifications]

Well the output signal goes up to 400A but really only one way to know for sure...

400A?

There is absolutely no way I would approach 400A on the battery terminal. I would never assume my battery is good in a Tesla - however in an ICE car....I wouldn't care.

If anyone has a bad or semi-bad battery...then I would be depending on MOSfets to protect my penthouse/main battery pack? No way.

However - if anyone has an extra $1k+ laying around to possibly blow a VCfront and have it replaced (Tesla install only) - test away.
BTW a broken VCfront is a bricked car.

 

[JWardell]

I read that wrong, I thought you were talking about the positive terminal in the penthouse.
The maximum current you should draw from the positive battery terminal under you hood is zero.

 

[modifications]

I read that wrong, I thought you were talking about the positive terminal in the penthouse.
The maximum current you should draw from the positive battery terminal under you hood is zero.

We have had many cars in the service center for repair due to people accidentally shorting out a 12V penthouse tap. Average cost for repair is $800.

Although I wouldn't pull 400A from the 12V battery under the hood. I would certainly use the 12V battery terminal for accessories rather than the penthouse. At least using the 12v battery as a source gives you the protection of VCFronts MOSfets against shorting out the penthouse.

As you probably already know:

The penthouse feeds VCfront and then VCfront feeds the 12V battery under the hood. If you look below - you will see a pic of VCfront as it receives power from the PCS (penthouse) and then distributes that voltage around the vehicle. namely the 12V battery ( red ) Pay attention to the arrows.

A great short video for everyone is this Tesla low voltage video.

 

[modifications]

One thing that everyone should consider is the function of the device they want to connect. If the function of the device that they want to connect ALWAYS runs.... then you would want to be aware that it might keep your vehicle from sleeping.

Teslas don't sleep for the same reason that humans sleep. One of the major reasons that Tesla's shut off (sleep) occurs is to keep the main battery from discharging and lose range as it sits doing nothing.

If your device is always running, then you might lose range a lot more than what you would want or expect.
For example: There are 2 vendors that supply the 2018 model 3 with the opportunity to have a motorized trunk release. One vendors' accessory allows the car to sleep and the other one doesn't. Of course you wouldn't know that from simply looking at the website or the box. Its only when you hook them up that you become aware.
One device sits there constantly watching to see if a person is moving their foot to open the trunk which is a constant current pull. The others device does not. I'll just leave it at that. i have had at least 70+ people this year come back to me after Tesla rejected their warranty repair due to the trunk release device that keeps their vehicles awake. I simply disconnect the device and re-attach their original struts and Tesla then services their warranty.

Anywhoo - I could go on and on about this kind of stuff, but keep in mind that what you add to your vehicle could potentially keep Tesla from working on your warrantied vehicle and/or keep your car awake to the point of losing range.

 

[JWardell]

We have had many cars in the service center for repair due to people accidentally shorting out a 12V penthouse tap. Average cost for repair is $800.

Although I wouldn't pull 400A from the 12V battery under the hood. I would certainly use the 12V battery terminal for accessories rather than the penthouse. At least using the 12v battery as a source gives you the protection of VCFronts MOSfets against shorting out the penthouse.

As you probably already know:

The penthouse feeds VCfront and then VCfront feeds the 12V battery under the hood. If you look below - you will see a pic of VCfront as it receives power from the PCS (penthouse) and then distributes that voltage around the vehicle. namely the 12V battery ( red ) Pay attention to the arrows.

A great short video for everyone is this Tesla low voltage video.

View attachment 40697

You are recommending people short their 12v battery? That will likely cause a FIRE.
Always add a fuse immediately at the location you tap any high current supply.
Ingineer strongly recommends you avoid tapping the 12v battery as well.

 

[apster]

So is there any consensus on connecting a simple amp/sub through the front battery? Apparently my car audio shop here has done it only through there with no problems?

 

[dingmah]

Bump from the dead.
I'm looking to install a 12v cigarette tap using the DC DC penthouse under the rear seats.
I want to do this, so I can plug in a rear dash cam or maybe power a small 12v fridge on long road trips.
Does anyone see any potential issues with this?

NOCO 12V Plug w/ Eyelet Terminals

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I

 

[Feathermerchant]

Rear Dash Cam???
My Model 3 nd Y already have that and more. 4 cameras. Built in.

 

[talkkyy77]

Thanks so much for posting this

 

[remixmark]

So is there any consensus on connecting a simple amp/sub through the front battery? Apparently my car audio shop here has done it only through there with no problems?

Just incase you haven't done this yet, here's how I wired up my amp and sub:

 

[remixmark]

How to remove the cover under the dash?

Don’t bother with this. Use the center console wire like I show in my post.

 

[Turmix]

Hello, I have a 2019 model 3 SR+, does anybody use the « trailer » 12v switched alimentation located under the rear bumper for a sound amplifier? It seems to be large enough imho, no?

 

[Teslalove]

For those of you looking for a nice switched 12v output for add-on accessories in your 3, I have found a good safe place to attach. See my YouTube video.

See the video's description for more details on this as well.

If you want a non-switched line for a dashcam, you can tap the yellow wire that feeds the overhead light/hazard switch console. The black wire on the opposite corner is ground.

It's going to ware on the Battery may even reduce Range.

 

[LieutenantColumbo]

Just wanted to thank all the trailblazers in this thread and also on Tesla Motor Club!

For those of you who have a 2024 MYLR from Austin, I can confirm that there is switched power source in the passenger side footwell. The power comes on when you sit in the driver’s seat and press the brake. It goes off when you exit the vehicle. You can see from the picture it was the thicker of two wires in the cable channel that were right on top of the bundle. I didn’t have to do any digging at all to get to it. To me it looks like it has an orangish tint to it. I just stuck a pin in it to pierce the insulation and validated that it was off with a 12v test light. Then I made sure it came on when seated in the driver's seat with the brake depressed.

I wanted a switched source for my Echo Auto as the existing Tesla USBs seem to stay on and I kept getting notifications that Echo Auto was ready to drive. I hooked up DC to USB A converter. I had a quick disconnect and an inline fuse on hand, so I added those into the harness. I used a blue Posi-Tap to make the connection to the switched 12v power source. There is a large ground bolt (10mm) in the door jamb that I loosened and slid a spade fork connector into that for the ground. Since there were 2 USB A connections with this converter, I now have a spare underneath the glovebox TBD. I didn't use a relay since I don't think this setup will be drawing much power. The converter accepts input power from 12v - 24v so I didn't have to worry about whether the voltage is running +15v.

 

[Rub"Y"]

Did you measure the voltage at that point? does your car have a lead acid or lithium battery which is 16 Volts?

 

[LieutenantColumbo]

Did you measure the voltage at that point? does your car have a lead acid or lithium battery which is 16 Volts?

Low Voltage Battery Type = Lithium-ion. I did not mot measure the voltage as it was irrelevant since my USB A converter has a 12v - 24v input.

Going to use the second USB A plug for my Uniden R3.