Frunk Auxiliary Power Tap / Power Feed Specs (48V and 400W)

[Timelord]

The low-voltage battery is to power the system when the vehicle is sleeping (i.e., the main pack contactors are open). If you're using accessories, then the vehicle is most certainly awake, with the main pack engaged and DC/DC available.

Beat me to it. This, definitely.

Battery is probably also the last resort power to get the car stopped while under control in a main battery failure incident.

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[Rutrow]

In the Monroe video they did say you can jump at 48V and 12V.

I'd be very cautious connecting to the battery as I mentioned before, because if the SbW setup. Its not just a short to be worried about, it's also brownouts, noise etc.

Pete Bannon didn't say you could jump with 48v, he said the converter takes current from the jump post from the 12 volt battery then makes the jump to 48 volts.

 

[scottf200]

The low-voltage battery is to power the system when the vehicle is sleeping (i.e., the main pack contactors are open). If you're using accessories, then the vehicle is most certainly awake, with the main pack engaged and DC/DC available.

Beat me to it. This, definitely.

Battery is probably also the last resort power to get the car stopped while under control in a main battery failure incident.

When I'm road tripping, I have sentry mode on so even when I'm not in the car (on), it is idle/awake but not sleeping. I think there are different levels/states tho that turn various subsystems off to lower the vampire drain. My TMX has changed a LOT since 2017 in this regard as they've determined how to make it "idle" more of the subsystems. I'm having WAY less vampire drain these days and it progressively got better under the same parking condition while not road tripping.

 

[JBee]

So still both right?

12V with converter 48V without?

 

[scottf200]

So still both right?

12V with converter 48V without?

Yes, that is the way I heard it. It only makes sense if your spouse's CT needs to jump your CT
[ala one Cybertruck jumps another Cybertruck]

 

[JBee]

I'm afraid it is very different than an alternator in the sense that the DC-to-DC can be triggered whenever they deem it necessary. I'm guessing you don't own a Tesla? It is well known that the Tesla cars monitor the 12v level and kick in the DC-to-DC to top it off. Lot of forum info on this on TMC as people put in always on Dashcams or fridges or whatever (running off low voltage battery when car is off / contacts open). I have a 12v fridge in my TMX as an example that I leave on 24x7 while road tripping. I have a battery monitor [URL] that is very very low amperage and takes a sample every minute or so. You can connect your phone and see graphs of the DC-to-DC kicking in over 24 hr periods or over a couple-week timeframe. HTH

Sorry, my alternator analogy was just in regards to how an alternator only runs on when you start the engine. Similar to when the main pack and motors are engaged.

A Prius also starts the engine and charges the battery when it gets flat, it also has a DC converter from the main pack to run assesories and a electric heat pump for air-conditioning.

This is 20 year old tech. Tesla didn't invent this.

To clarify, my main point was simply that it makes no sense to charge the 48V battery from the main pack whilst the main pack (aka ICE engine) was on. Any load would be better and more efficiently served directly from the main pack via the DC converter directly to the accessory. This avoids further losses from charging and discharging the 48V battery.

 

[Wamblyhorse]

They claim 400 watts for the frunk in the latest T-Sportsline video.
(400 watts) / (48 volts) = 8.3 amperes

T Sportline: "Confirmed with Tesla, both [roof | frunk] auxiliary power taps are rated to 400 watts. Both are protected with solid state circuits, if you exceed 400w, they shut off."

Title: Dissecting a Cybertruck Part 2! Tesla Auxiliary Power Under Frunk, Inspection & More, first look
7:26

Oh yeah? Well, the 48V ain’t gonna be enough power for this bad boy! 4ea 280kW motors on top of 2ea 100kW motors, for 1,320kW of power required. Oh sure, you’ll need an aftermarket bumper to mount it on…

The 16,500lb Warn winch pulls 507 amps…

https://www.warn.com/165tis-heavyweight-winch-97740

maybe this would work on 48 volt?

 

[wanders]

Best way forward for these higher power accessories would be installing a dedicated battery and charging it from the frunk power feed connection.

Sounds like a missed opportunity

 

[scottf200]

maybe this would work on 48 volt?

>>> They claim 400 watts for the frunk in the latest T-Sportsline video.
>>> (400 watts) / (48 volts) = 8.3 amperes

The video showed them pulling 8 amps from the battery at the lowest speed then 16 amps then 24 amps.

 

[Rutrow]

I would think that Tesla has prewired this tap for some specific accessory they have in the works. Let's all just speculate what that will be. My guess...

 

[Kahpernicus]

What's weird is the harness on EPC doesn't even point to the wires. Unlike the roof accessory.

 

[kbolt]

They claim 400 watts for the frunk in the latest T-Sportsline video.
(400 watts) / (48 volts) = 8.3 amperes

T Sportline: "Confirmed with Tesla, both [roof | frunk] auxiliary power taps are rated to 400 watts. Both are protected with solid state circuits, if you exceed 400w, they shut off."

Title: Dissecting a Cybertruck Part 2! Tesla Auxiliary Power Under Frunk, Inspection & More, first look
7:26

Is this the new Sandy Monroe?

 

[scottf200]

Is this the new Sandy Monroe?

Nope, just an after-market company with a couple of celebrities Cybertrucks and they are striking while the iron is hot. Sandy has some brilliant folks working for him and I love their analysis and overviews (not so much Sandy's)

 

[ModelCYBR]

My 48v frunk lines are no longer providing any power after hooking up a 48v -> 12v step down converter. Flipping outlets and mods switch on and off and waiting a few hours still yields nothing. Didn’t put any loads other than reading voltages off multimeter. Odd as I thought these were fuses and would reset automatically.

any ideas how to further debug? Nothing useful I’m seeing when in Service mode either.

 

[scottf200]

My 48v frunk lines are no longer providing any power after hooking up a 48v -> 12v step down converter. Flipping outlets and mods switch on and off and waiting a few hours still yields nothing. Didn’t put any loads other than reading voltages off multimeter. Odd as I thought these were fuses and would reset automatically.

any ideas how to further debug? Nothing useful I’m seeing when in Service mode either.

Did this change after an OTA was applied?

I thought so to starting with the TM3.

Ingineer said (TMC):

There indeed are zero fuses on the 12v side. All circuit protection is performed solid-state, which in practice means a transistor (MOSFET) is used to switch all the loads, and the body controllers monitor the current going though each of these and in the event of an overload, it just switches off the transistor. It's much faster and safer, and allows a more reliable and easy to diagnose car. It is more expensive, but this was needed to make the M3 fault tolerant to achieve full self driving with confidence.

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