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SeaGeo

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One issue is there probably isn't a single battery temp. They could give the average as an estimate.

And hopefully the range isn't that great, otherwise they have thermal design issues lol.
I'm sure there is. They could show min/max or something. My ID.4 reports... 3 IIRC.

Well, if you start driving at say... 30 degrees outside, the battery may very slowly warm up (or not at all). So it's a good telltale why it may be charging slowly if you aren't getting it up in that 80 degree range. That was a fantastic little tool to figure out why everyone's ID4 started having DCFC charging issues in December.
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Forager

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See the video I shared above.
If you're somewhere remote and have access to a gas/diesel tow vehicle, it's a totally plausible rescue scenario and it's going to be more efficient to tow charge than to tow in neutral. Of course it shouldn't be a common/primary scenario for anyone and definitely not something you'll ever do unattended, but if you're doing a big overland crossing and run out of charge, a brief rescue tow could give you enough independence to drive the rest yourself. (At the expense of your dignity.)
Under no circumstance would it be more efficient to charge tow a vehicle than towing in neutral. The regenerative braking energy being used to charge the batteries of the trailing vehicle is being applied as a drag on the tow vehicle, and the regenerative charging isn’t 100% efficient. To generate a 50 kW charge on the batteries, the regen is probably creating 58 kW of drag on the tow vehicle (or more), plus whatever energy is needed to tow the dead vehicle in the first place.
 

kylealden

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Under no circumstance would it be more efficient to charge tow a vehicle than towing in neutral. The regenerative braking energy being used to charge the batteries of the trailing vehicle is being applied as a drag on the tow vehicle, and the regenerative charging isn’t 100% efficient. To generate a 50 kW charge on the batteries, the regen is probably creating 58 kW of drag on the tow vehicle (or more), plus whatever energy is needed to tow the dead vehicle in the first place.
Sorry, I was perhaps unclear. You're right that in net energy transfer it can't be more efficient to regen-tow than flat-tow per mile.

But, if you need to move an EV and ICE 10 miles, it's more efficient to tow charge the EV for two miles and drive the remainder on battery than to neutral-tow it for ten miles.

The energy transfer is lossy, but the EV is 5-10x more efficient at harnessing that energy than the ICE tow vehicle. So even with a lossy transfer, you're better off tow charging and then driving than just towing.

This is precisely that Engineering Explained was testing in the video I linked and the data supports it.
 

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Sorry, I was perhaps unclear. You're right that in net energy transfer it can't be more efficient to regen-tow than flat-tow per mile.

But, if you need to move an EV and ICE 10 miles, it's more efficient to tow charge the EV for two miles and drive the remainder on battery than to neutral-tow it for ten miles.

The energy transfer is lossy, but the EV is 5-10x more efficient at harnessing that energy than the ICE tow vehicle. So even with a lossy transfer, you're better off tow charging and then driving than just towing.

This is precisely that Engineering Explained was testing in the video I linked and the data supports it.
Ok, so I watched the video. It was fun, not quite Bill Nye the Science Guy, but entertaining. However, they overlook two items which are important for forming a final argument *either* way:

1) Both vehicles need to make it from A to B (not just the Tesla)
2) They never checked the efficiency of the truck towing the Tesla in neutral, which is more efficient than this regenerative scenario

Depending on the efficiency of item 2, the regen tow will be the least efficient method of getting both vehicles from A to B.
 

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Wait...I'm confused. I click on a YouTube video that shows an R1T towing an old Ford and what I get is two dudes chillin on their deck. Where's the video of the Rivian towing the Ford?
 

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camaroz1985

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Wait...I'm confused. I click on a YouTube video that shows an R1T towing an old Ford and what I get is two dudes chillin on their deck. Where's the video of the Rivian towing the Ford?
Like everything Rivian related..... s00n.

They said it is still being edited. They posted a Toyota Sequoia video today, so maybe tomorrow.
 

R1T7777

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You don't really "gain" much battery from downhill sections, it's more that you get those sections for free. Regen is limited in how much energy it can absorb at any one time to avoid stressing the battery, so you don't get a massive boost from downhill sections vs any other braking. It maxes out at something like -2 or -3 kWh/100 mi in the EVs I've driven.

But you get the mix of free range and a slight regen, so it maths out to a massive efficiency gain.
My Bolt will regularly regen at 50kW on downhills, which is as fast as it charges on DCFC. I'd hope the R1T would do as well or better with AWD and more mass.
 

Florida Boy

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One issue is there probably isn't a single battery temp. They could give the average as an estimate.

And hopefully the range isn't that great, otherwise they have thermal design issues lol.
I think the battery temp would be interesting, but I'm not sure what the average user would do with that information. How would they know what an 'optimal' recharging temp even is? And what would they do about it if they have to charge? And as you said, there are thousands of batteries organized into several modules to make up a pack.

Seems like one of the functions of a good BMS should be to abstract this from the user and just be ready to charge before they reach a charger.
 

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@TFLtommy is Rivian week longer than 7 days?
Hopefully, you guys didn't run into any issues editing that Ike video with the R1T....
 

ajdelange

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The energy transfer is lossy, but the EV is 5-10x more efficient at harnessing that energy than the ICE tow vehicle. So even with a lossy transfer, you're better off tow charging and then driving than just towing.
The energy that moves the towed vehicle ultimately has to come from the towing vehicle. Is it more efficient to just apply that energy to the towed vehicles wheels to move it or convert it to electricity, rectify that, charge a battery with it, discharge the battery, invert and run a motor?
 

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BigE

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@TFLtommy is Rivian week longer than 7 days?
Hopefully, you guys didn't run into any issues editing that Ike video with the R1T....
Kind a bit worried…Did Rivian possibly have an issue with their results and thus no Ike video? Hopefully not and we’ll see something soon.
 

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Kind a bit worried…Did Rivian possibly have an issue with their results and thus no Ike video? Hopefully not and we’ll see something soon.
TFL has been pretty clear that Rivian doesn't have any editorial oversight on these videos (and there's no reason to suspect that they would). There are a thousand mundane reasons this could be taking a bit longer than planned - no need for conspiracies.
 

BigE

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TFL has been pretty clear that Rivian doesn't have any editorial oversight on these videos (and there's no reason to suspect that they would). There are a thousand mundane reasons this could be taking a bit longer than planned - no need for conspiracies.
Fingers crossed ??
 
 




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