Trailer left connected maintains Rivian's 12V battery?

[SwampNut]

So Ford, Chrysler, everyone else ignores safety? Or maybe they know it's still far safer to use adaptive when towing than driving manually? You know, like pretty much every semi-truck uses too? (And I leverage that, by merging with them and just forming a group all with adaptive.)

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[IGR]

So Ford, Chrysler, everyone else ignores safety? Or maybe they know it's still far safer to use adaptive when towing than driving manually? You know, like pretty much every semi-truck uses too? (And I leverage that, by merging with them and just forming a group all with adaptive.)

I cannot comment what everyone else does, but you have to understand that those are different vehicles, with different teams of engineers and software developers behind them.
If I'm buying a 95 Honda Civic I wouldn't expect it to go 160 mph just because Porsche could.

 

[SwampNut]

Rivian ADAS is incredibly terrible so you do have a point there. There seems to be strong evidence that the adaptive in the Rivian is pretty much off the shelf and therefore used by others also.

 

[Dark-Fx]

I enjoy idiots telling me how I'm going to die in all sorts of ways, so that sounds fun. Keep in mind that I've owned and driven several vehicles that allow adaptive and/or full ADAS. For example, the Ford does. If I had been warned that Rivian was this stupid, there's a strong chance I would not have bought the truck. This is incredibly stupid of them.

So yes, I will be making a circuit to hide the trailer from the truck. Should be fairly easy and probably $50 in parts, or so. Using inductive sensing and/or opto-isolators. I'll make a new post for it.

I'm also the guy with the steering wheel weight in the Tesla.

I think you could make this work on a trailer that doesn't have brakes. I'm guessing you can't make it work if you actually need the trailer brakes. I have a secondary harness wired into my R1T for a third brake light/turn signals. Using inductive loops on the wires coming off the brake lamps of each side. Usually works fine, occasionally a lamp won't fire when it should. Resetting the light controller re-learns it so it'll work after that.

I've done some very preliminary testing on hijacking the signal right out of the trailer plug harness. I *think* the lighting circuits are doable with the correct circuitry. Rivian constantly supplies a low voltage that they are using to check when a trailer gets plugged in, but the turn/brake signal still seems to transmit when it doesn't detect anything. I don't remember exactly which wires I had tested and shelved the project at the time.

Feel free to start your own thread on it and I'll contribute what I can there.

 

[Davethadog]

Annoying tangential arguments aside, as long as the circuit stays open when the truck is off and your trailer doesn’t close its side, it makes sense that that the trailer would provide current back to the 12v battery and the potential would equalize.

 

[Marchin_MTB]

So Ford, Chrysler, everyone else ignores safety? Or maybe they know it's still far safer to use adaptive when towing than driving manually? You know, like pretty much every semi-truck uses too? (And I leverage that, by merging with them and just forming a group all with adaptive.)

No, it’s just that the Rivian software may not be ready yet. You would agree that the vehicle dynamics are very different with a trailer attached. My guess is that Rivian hasn’t tested their ADAS in this use case yet. Also, even though it’s very rare, the consequences of phantom braking are much more severe with a 7000lb box behind you.

 

[Marchin_MTB]

Annoying tangential arguments aside, as long as the circuit stays open when the truck is off and your trailer doesn’t close its side, it makes sense that that the trailer would provide current back to the 12v battery and the potential would equalize.

Agreed. What I’m a little worried about then is leaving a trailer connected that has a low SoC battery for a day or two and that then draining the 12V on the Rivian.

 

[SPITmadFIRE]

So Ford, Chrysler, everyone else ignores safety? Or maybe they know it's still far safer to use adaptive when towing than driving manually? You know, like pretty much every semi-truck uses too? (And I leverage that, by merging with them and just forming a group all with adaptive.)

No one said other automakers ignore safety. The assumption is that those systems are designed, engineered, tested, and maintained to support towing since it explicitly allows it. Any system that explicitly prohibits use while towing is done so deliberately. Whether that's because there are serious known issues with the system while towing or just a lack of testing is not a bet I'm willing to make at highway speeds whether I'm in the vehicle with you or the vehicle next to you.

 

[SSteveEV]

So... would this translate to plugging in another battery in the gear tunnel via the 12V for reduced drain of the HV pack? Or does that turn off with the truck?
Will be watching your investigations because I'd consider that if it saved a few % while parked.

 

[Dark-Fx]

So... would this translate to plugging in another battery in the gear tunnel via the 12V for reduced drain of the HV pack? Or does that turn off with the truck?
Will be watching your investigations because I'd consider that if it saved a few % while parked.

I blew that fuse in my truck and have been too lazy to fix it, or I'd check there too.

Leaving my truck parked by itself for a few days to get a baseline on drain, then going to try to see if I can duplicate this just using a supplemental 13.6V supply plugged into the trailer hitch power, with a logging device to see how much energy is consumed.

 

[Budman]

Annoying tangential arguments aside, as long as the circuit stays open when the truck is off and your trailer doesn’t close its side, it makes sense that that the trailer would provide current back to the 12v battery and the potential would equalize.

Here's tangential;

I noticed that when I plug in my supplemental LED light bar that I bought on Amazon, the turn signals on the light bar are delayed by one blink. Then, when you step on the brake pedal one turn signal blink lights up before the brake lights illuminate. It appears a turn signal command gets left in computer memory then released to the hitch outlet when the brake is pressed.

tangential but curious.

 

[CharonPDX]

That is interesting. Haven’t been connected to our camper while parked long enough to notice anything. Also, our camper has no way of displaying load information.

Could this work the other way? If the camper batt voltage is low, would the Rivian charge it via that hitch connection?

Absolutely. Rivian will keep 12V system running if the vehicle is "awake" (doesn't even have to be "on") and power the trailer.

 

[Riviaenz]

It doesn’t surprise me. Not unlike putting a battery maintainer on the 12v circuit via a “cigarette” lighter. Or in this case via the jumper leads.

Right, it’s totally possible given that the 7 pin blade in the back of the Rivian can be used to re-energize the 12v system if needed (dead 12v), or officially, there are cables behind the blank next to the 7 pin blade that can be accessed to “jump” the 12v system.

The official method is (starts at 1:01):


The ”harder” method using the 7 pin blade:


What’s interesting is that the @Dark-Fx seemed to attribute zero drain on the HV battery to their trailer being plugged into their R1. I’m not aware of a trailer backfeeding enough energy back through the plug to sustain the HV battery (seems unlikely given the huge uphill voltage differential). I suppose It could be if there are solar panels or other source through the power pin on the 7 pin blade to at least power all LV systems without the converter needing to sustain the 12v system. I’ve not noticed it but I’ve also not left our trailer plugged in overnight while camping.

We have another trip coming up next weekend. I am curious and will keep an eye out for it.

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