Split the 48v power line to a 12v socket in frunk. It now powers the console fridge INSIDE cabin 😎

[hemiarch]

It's not a runaway process as long as the frunk can lose heat to the environment faster than heat enters the cooled compartment.

The frunk lid is around ten square feet of single layer stainless steel.
Stainless steel has a thermal conductivity of ~14W/mK. At a thickness of 1.8mm (0.0018m), that's an R value of .000125. Mixing units for simplicity: 1/R*10 = 80,000 for thermal transfer

A 24x14x14 cooler is 12 ft² of area. With R-3 insulation, that's 1/3*12 = 4 units of thermal transfer.

The frunk sheds heat 20,000 times better than the cooler gains it. If the cooler wants to be 34 degrees and the world is 90, the air in the frunk needs to be barely over 90 for the cooler to work. As long as it can handle a 56 degree differential (which it should) things will work fine.

Facts always win. At least, that used to be the case.

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[TraileringButtocks]

But don't you have to include the air between the fridge and the frunk? Your napkin analysis assumes (I believe) that the heat is directly transferred from the fridge to the stainless, but it isn't. Maybe someone can set this up on ICEPAK!

 

[hemiarch]

The napkin engineering is indeed fun but real world I believe @sean3d2 runs a fridge in his frunk. Very cool setup.
if available maybe he can post some pics and explain what he does.

 

[mongo]

But don't you have to include the air between the fridge and the frunk? Your napkin analysis assumes (I believe) that the heat is directly transferred from the fridge to the stainless, but it isn't. Maybe someone can set this up on ICEPAK!

Heat is transfered from air to fridge. Heat is transferred from air to lid (and lid to air).
Assuming it's not stagnant, the air temp is fairly uniform.
Important point is transfer through the lid is much higher than into the fridge so temperature delta needed across lid is much lower.

 

[CyberGus]

I believe @sean3d2 runs a fridge in his frunk. Very cool

I see what you did there

 

[hemiarch]

I see what you did there

You’re smarter than that polar bear looks.
Or…the average bear at least

 

[CyberGus]

Important point is transfer through the lid is much higher than into the fridge so temperature delta needed across lid is much lower.

While the frunk lid is thermally conductive, warm air in an enclosed space will hamper efficiency. If I had a permanently-mounted installation, I might be inclined to install a small exhaust fan.

 

[TraileringButtocks]

Heat is transfered from air to fridge. Heat is transferred from air to lid (and lid to air).
Assuming it's not stagnant, the air temp is fairly uniform.
Important point is transfer through the lid is much higher than into the fridge so temperature delta needed across lid is much lower.

The heat is transferred from Point_A (fridge) to Point_B (air) to Point_C (stainless). You cannot simply ignore Point_B. Heat transfer is a 3D flux of course, but you can model it as a 2D resistor network (which we do in electronics all the time). So "Point_B" (so to speak) is a resistance represented by the air. But whatever, set aside the math and do this thought experiment. Put a 25W point source in the center of a 2ft x 2ft x 6ft stainless steel box, filled with air at 60F (same as outside air at 60F). What will be the temperature of the point source be at equilibrium? Now run the same experiment but fill the stainless box with water. What's the temperature of the point source at equilibrium in this case?

But whatever. Running a small fridge in the frunk likely is just fine (unless maybe you live in the Death Valley). But napkin math of the thermal conductivity of stainless doesn't prove that though (you could probably coat it with 1cm of ceramic and it would still be OK). Later, man.

 

[BrockN]

Cool. Thanks j.
Question, if I split off before the buck converter, I can have both a 48v frunk power supply through that Anderson connector and also 12v output after the buck convertor going to the cabin right?

You can get Anderson PowerPole connectors in different colours. I suggest that if you plan to have one with 48 volts on it, a different colour might be a good idea.

I've been procrastinating on doing what Leo did since the truck arrived... I have a 50 Ah LFP battery that I charge up once in a while and that does the job, but if I confirm that the 48 V circuit isn't noisy (radio noisy) like the 120 V one is, a more permanent solution might be cobbled together.

I need more amps inside than Leo does, so I will likely bring the 48 V into the cab as you were implying. Tesla went to 48 V in part to save on wiring. So I can bring in the 48 V with 16 AWG (maybe 14 if I want to pull full current continuously) and use all 400 available Watts. The buck converter would be inside. If I left the buck converter where Leo has it, I'd need 10 AWG, and possibly 8 AWG into the cab, which would be a pain to route and hide.

I like these things: https://www.westmountainradio.com/product_info.php?products_id=rr_4005h_c and really appreciate the individual fusing.

They also have something for 48 V, but I'm not seeing a use case for this - yet... : https://www.westmountainradio.com/product_info.php?products_id=rr_4008hv_p48 If someone makes a Bluetooth remote switch that can handle 48 V, I'll be much more interested.

As far as buck converters go, they advertise 12 V typically. Some may produce that, some are adjustable, some may output 13.8 V. Since ICE is typically 13.8 V but 'identifies' as 12 V system, I'd make sure the device is actually 13.8 so things like inflaters and lights that are designed for a cigarette lighter socket get the full voltage they need.

 

[stebb1174]

Get any converter with 4+ stars and more than 30 to 40 reviews. They're all pretty much the same, made in China, you just need 48 to 12 V. The solution I saw from T-sportline looks identical to what I picked, but with Deutsch connectors preinstalled (if I'm correct) and the mount.


Anyone have any experience with the Tsportline buck converter? I just got it but was surprised to see how small the wires were. They are 18AWG DT connectors. I don't think they can handle both the refrigerator and frunk outlet.

Any suggestions as to which buck converter to use?

Thanks

 

[hemiarch]

You can get Anderson PowerPole connectors in different colours. I suggest that if you plan to have one with 48 volts on it, a different colour might be a good idea.

I've been procrastinating on doing what Leo did since the truck arrived... I have a 50 Ah LFP battery that I charge up once in a while and that does the job, but if I confirm that the 48 V circuit isn't noisy (radio noisy) like the 120 V one is, a more permanent solution might be cobbled together.

I need more amps inside than Leo does, so I will likely bring the 48 V into the cab as you were implying. Tesla went to 48 V in part to save on wiring. So I can bring in the 48 V with 16 AWG (maybe 14 if I want to pull full current continuously) and use all 400 available Watts. The buck converter would be inside. If I left the buck converter where Leo has it, I'd need 10 AWG, and possibly 8 AWG into the cab, which would be a pain to route and hide.

I like these things: https://www.westmountainradio.com/product_info.php?products_id=rr_4005h_c and really appreciate the individual fusing.

They also have something for 48 V, but I'm not seeing a use case for this - yet... : https://www.westmountainradio.com/product_info.php?products_id=rr_4008hv_p48 If someone makes a Bluetooth remote switch that can handle 48 V, I'll be much more interested.

As far as buck converters go, they advertise 12 V typically. Some may produce that, some are adjustable, some may output 13.8 V. Since ICE is typically 13.8 V but 'identifies' as 12 V system, I'd make sure the device is actually 13.8 so things like inflaters and lights that are designed for a cigarette lighter socket get the full voltage they need.

Thanks for the very valuable post. The 48v box is sort of what I envisioned but a little smaller. I’m going to send 48v to the frunk for the power station and 48v into the cabin for Starlink mini. Will probably put a small buck behind the fridge to power it and my LED eyes in my bed as a dc hardwire. Any other 13.6v I need I’ll get from either the power station in my frunk or the one in my vault.

 

[hemiarch]

Get any converter with 4+ stars and more than 30 to 40 reviews. They're all pretty much the same, made in China, you just need 48 to 12 V. The solution I saw from T-sportline looks identical to what I picked, but with Deutsch connectors preinstalled (if I'm correct) and the mount.


Anyone have any experience with the Tsportline buck converter? I just got it but was surprised to see how small the wires were. They are 18AWG DT connectors. I don't think they can handle both the refrigerator and frunk outlet.

Any suggestions as to which buck converter to use?

Thanks

I’m no expert but based on past experience with the brand, this seems like a pretty good choice.
https://a.co/d/dwfq3g4

 

[BrockN]

I’m no expert but based on past experience with the brand, this seems like a pretty good choice.
https://a.co/d/dwfq3g4

Hard to decide exactly what this device is capable of from the description, but I think it's rated at 12.2 V nominal. If I was looking for one of these, I think I'd look for something that states 13.8 v output explicitly. That Victron supposedly allows you to adjust the output voltage, but that might result in a compromise elsewhere (heat, current, whatever). Also, the Bluetooth connectivity... what's that for, really? I would also look into the range that the Cybertruck will give you on the 48 V circuit. I seem to recall a fairly wide range, up as high as 56 V maybe? I've seen that information somewhere but can't put my fingers on it now. The buck converter needs to be able to handle the range the Cybertruck will give it.

My gut says you can find something more tailored to this purpose for less money.

 

[hemiarch]

Wanted to share what I think is a good find and I figured anyone who would be interested in it probably follows this thread. Thanks again @Leo Snow.
This guy apparently can be wired directly to 48v.
https://a.co/d/ehvdYQy

 

[hemiarch]

Wanted to share what I think is a good find and I figured anyone who would be interested in it probably follows this thread. Thanks again @Leo Snow.
This guy apparently can be wired directly to 48v.
https://a.co/d/ehvdYQy

Jay and I redid my wiring together today. Happy with the outcome. Installed an aux beam switch for control of the cabin fridge, Starlink mini and smugglers den fridge. Also powered my small power station in the frunk for any electrical needs there. Have a leftover 12v source capped in case I was to add anything else.
Tried your method but still ended up going through the grommet. It’s a good approach but I don’t like how the wires sit on the sharp edge under the rubber door seal.

The last one is of the fish tape following the wire path. A picture wish I had grabbed the first time.

Thanks again for the inspiration.

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