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

[ModelCYBR]

Yes after I got 2024.8.4

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[scottf200]

Did this change after an OTA was applied?
I thought so to starting with the TM3.
Ingineer said (TMC):

Yes after I got 2024.8.4

Well that could be important information. Possibility that they turned it off or changed something on how it works. Perhaps they are testing it more or verifying it based on issues they've had with users using it on various applications.

 

[Feathermerchant]

I am building a 12V 300A supply using 3 server power supplies in parallel and planning to power them from the CT's 240V in the bed. My 12,000 lb winch says it can draw just a little over 300A so this should work for all but the worst case. Only concerns are for the 240V if it is raining.

 

[tbuck]

I am building a 12V 300A supply using 3 server power supplies in parallel and planning to power them from the CT's 240V in the bed. My 12,000 lb winch says it can draw just a little over 300A so this should work for all but the worst case. Only concerns are for the 240V if it is raining.

Check your winch, many of them will pull 600 Cold Crank Amps when they start. The CT's 240V (and 120V) outlets are limited to 40A - as long as the drop down DC-DC conversion does not exceed this, you may be fine.

Another option is to drop in a deep cycle battery (like an Optima Yellowtop with 750 CCA) and just use a trickle charger on the CT to keep it topped off.

 

[Feathermerchant]

Trickle charger probably not But 20A chargers are available. Yes the start amps is a lot. I may have to use an alternate way to start it. Like a soft start on an AC motor. What we need is a good 120 or 240V winch.

 

[ModelCYBR]

I’ve finding nothing in the service manual about these 48v accessory ports. I am going to check again after it’s been asleep for 12-15 hours and see if I have voltage again. Then I will try a full power off and if not then I will disconnect the 48v battery.

stay tuned.

 

[ModelCYBR]

https://service.tesla.com/docs/Cybe...UID-A399E8AE-5DCF-4095-91FA-AF0148503F3B.html

This did the trick, I have power again.

44.4v is the reading (about 2v lower than yesterday) but will keep eye on it.

 

[scottf200]

https://service.tesla.com/docs/Cybe...UID-A399E8AE-5DCF-4095-91FA-AF0148503F3B.html

This did the trick, I have power again.

44.4v is the reading (about 2v lower than yesterday) but will keep eye on it.

Aw same trick with some other Teslas (and non-Teslas) for a 'hard reset' - disconnect low/mid-voltage battery for a couple of minutes. I've had to do that on my TMX a few times (get GPS to work/locate properly).

Odd the MOSFET auto-reset didn't happen.

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.

 

[ModelCYBR]

Now still any of the dc-dc step down reducers I connect trip the efuse. I have 3 different ones from 3 different brands. No loads attached. I’m guessing there is some voltage leakage back into the 48v line or something that is causing the fuse to trip. I’m no EE so anyone’s guess. Maybe an isolator of some sort is needed?

 

[scottf200]

Now still any of the dc-dc step down reducers I connect trip the efuse. I have 3 different ones from 3 different brands. No loads attached. I’m guessing there is some voltage leakage back into the 48v line or something that is causing the fuse to trip. I’m no EE so anyone’s guess. Maybe an isolator of some sort is needed?

This seems pretty weird to me and would have guessed that Tesla would have anticipated users would be doing a:
- step down to 12v products (tools/accessories)
- step up to 120v products (tools/accessories)
I must be missing something.

 

[ModelCYBR]

Yea literally have the most simple setup possible and no luck. It must be super sensitive to voltage fluctuations and thinks there is a ground fault and trips the fuse. Almost like GFCI maybe. I'm ordering yet another DC-DC converter. An isolated on from Victron. If that doesn't work I don't know what to do.

 

[ModelCYBR]

further tracked this down and think I have an answer… when continually pulling power from the 48v line (50 watts or so) THEN attaching the dc step down device, there are no issues.

The efuse is perhaps seeing the small load (a few milliamps when the resistance builds up in the converter) and trips by thinking there is a small short vs. when there is more current being pulled it has no issue.

 

[Feathermerchant]

Most DC-DC have a pretty large capacitor across the input for filtering. That looks like a dead short initially and is probably what is tripping the protective circuit.
As far as reset, that is software. My 2011 F150 has fuses but also FETs in the Body Control Module. Each time the circuit is tripped it resets automatically and increments a counter. After so many counts, it stays tripped but can be reset with software. after too many trips, the BCM has to be replaced.
SO it really depends on software.

 

[SentinelOne]

Ok, my company (Im the CIO not a product expert or even close) makes sophisticated power supplies for Semi Conductor, Hyperscalers, Industrial & Medical applications - aka not home use and not amazon. I pinged engineering on do we have or can we do something that could work....problem is I cant articulate it correctly...with me fudging through, here's first response I got..

" A Basic 48V:12V, IP sealed box, constant current, fold-back power-limited product with Screw terminations would be kind of simple.. but we could add in a cigarette lighter connector (with a power-limit applied)… The base power converter I have in mind is digital-controlled, so, I’m wondering if blue-tooth connection to the power-converter would be an interesting add-on (Monitor and control functions)… It’d be easy to add in a USB or 2 as well… I guess the size of it – I’m guessing 4” by 4” by 1”… I’d look to thermally bond the module to the inside of the IP sealed box with fins on the outside of it… probably anodized with a ‘nice’ coating… I’d add in a little bit of EMI filtering as the 48V is shared in the vehicle (but I don’t know EMI-spec’s for EV’s) and maybe a little bit of hold-up…"

I had asked for 12v Cig Adaptor/Screw Terminals - I want to hook up my RV air compressor that has aligator clips, etc....but im no designer.....given it'll be behind frunk wall, don't think we need the anodicizing or even waterproof? But what connectors or any other specs? aka what make sense guys and I'll ask for feasibility and prototype!

 

[Feathermerchant]

Sounds interesting. It looks like it needs to 'soft start' to keep the current minding bits in the CT happy. As far as a compressor goes, I'd look at tapping the onboard air in the truck or just carry a portable battery powered compressor.

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