Rivian technical nuggets gleaned from EPA application docs

[flabyboy]

It’s only money, the bank has lots!

smaller one is probably fine, just means more stops.

But I drive across Saskatchewan a lot and I treat it like driving through the bad part of town at night. Don’t stop if you don’t have to and don’t slow down ??

I'm not a fan of debt.

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[SeaGeo]

Just the range hit on the cold weather. I live at under 20F for a good three to four months of the year. I expected a hit, but not 40%. Guess I should have done more research

Are you able to plug it in over night?

 

[ajdelange]

Just the range hit on the cold weather. I live at under 20F for a good three to four months of the year. I expected a hit, but not 40%. Guess I should have done more research

Don't panic just yet. The statement that the cold weather "hit" is 40% is entirely meaningless as what "cold weather" means is not defined and the conditions under which one drives in cold weather aren't specified nor is the condition of the vehicle driven in cold weather given. Leave it outside to soak in -20 F overnight and drive it on a snow covered road with the heater on full blast and yes, I'll bet you'll lose 40%. I drive my car in 20F weather but it is kept in a garage at about 50 overnight and I don't see any noticeable loss.

 

[crashmtb]

I'm not a fan of debt.

me either, but that’s my response any time someone complains about costs ??

 

[ajdelange]

No heat pump

It does have a heat pump but not a reversible one.

but it might be more efficient to have a single switch. Both would have the effect of "rewiring" the pack from 108s 72p (nominal 400V & 360Ah) to 216s 36p (nominal 800V & 180Ah) while charging

It takes 3 switches to do this.

 

[Northish]

Not even a tiny bit. As it sits our primary car(focus RS) has worse range than the R1T “regular” battery.

That said, I am getting the max pack, to lengthen the legs some.

on a long trip we usually end up stopping every 2-4 hours anyway. So I’m not worried.

Fellow Focus RS daily driver here here from MN ? The range of the RS is about perfect as any more and we'd need to stop anyway for bathrooms and stretching a bit. We've done lots of long road trips with it now, the longest recently being over 5,000 mi. And there's the yearly road-trip to Copper Mtn. in the winter. Planning to do even longer trips with the R1T.

We're really on the fence though - Max vs LE w/ Large. Some days I wake up and think Max is a no brainer, others I think just stick w/ the less expensive LE and save $10k plus $1.8k for AT wheels. There should be more infrastructure coming to the Midwest by the time we would get our LE, right? It's a hard decision. You're making me lean back to Max, darn you.

 

[crashmtb]

Fellow Focus RS daily driver here here from MN ? The range of the RS is about perfect as any more and we'd need to stop anyway for bathrooms and stretching a bit. We've done lots of long road trips with it now, the longest recently being over 5,000 mi. And there's the yearly road-trip to Copper Mtn. in the winter. Planning to do even longer trips with the R1T.

We're really on the fence though - Max vs LE w/ Large. Some days I wake up and think Max is a no brainer, others I think just stick w/ the less expensive LE and save $10k plus $1.8k for AT wheels. There should be more infrastructure coming to the Midwest by the time we would get our LE, right? It's a hard decision. You're making me lean back to Max, darn you.

how many under-engine splash shields have you gone through? ?
Our longest trip with the RS was to Tofino, BC and back in Feb 2020. About 6000km all in.

I figure I can’t add more battery later, so max pack it is. Plus I missed the window for LE by a lot ?

Driving in western Canada I’ve always the mentality of getting fuel whenever the chance presents itself.

you‘ve already got better charging infrastructure due to density. Look at a charging map of Manitoba and Sask. Quite barren even compared to the prairie/midwestern states.
hilariously, the MB government touts all the block heater plugs in parking lots as “existing charging infrastructure that would cost billions to build”

 

[flabyboy]

Don't panic just yet. The statement that the cold weather "hit" is 40% is entirely meaningless as what "cold weather" means is not defined and the conditions under which one drives in cold weather aren't specified nor is the condition of the vehicle driven in cold weather given. Leave it outside to soak in -20 F overnight and drive it on a snow covered road with the heater on full blast and yes, I'll bet you'll lose 40%. I drive my car in 20F weather but it is kept in a garage at about 50 overnight and I don't see any noticeable loss.

I have a heated garage so I'm sure that will help at times. Other times I have to park my car in a shuttle lot for 12 hours and take a bus into work.

 

[Driveout]

Video Rivian walkaround 1:50 drag coefficient 0.3

 

[ajdelange]

I've explained earlier why Wh/mi is preferred to mi/kWh and the explanation I gave was that it is the natural unit for any computation we may wish to make. A dialogue I had here with a member a few months back came to mind. He wants to drive 27 miles on the beach and was concerned that he'd run out of battery. The potential killer here is rolling resistance. That is one of the easiest loads to compute as the force from rolling resistance is simply F = c*m*g in which c is a coefficient, m the mass of the vehicle and g the acceleration due to gravity. The R1T is massive at approximately (8500/2.2) = 3864 kg. On cement c ~ 0.01 so the force is 0.01*(8500/2.2)*9.8 and the energy required to overcome it in driving a mile is 0.01*(8500/2.2)*9.8*1603 N-m/mi = 0.01*(8500/2.2)*9.8*1603/3600 = 168.6 Wh/mi. From the EPA data we have 480 Wh/mi from the wall as the rated consumption which, with an assumed charger efficiency of 91% translates to 437 Wh/mi from the battery. Rolling resistance is a large part of this (38.5% of it). But this is on cement where c ~ 0.01. On sand c ~ 0.3. That's 30 times higher and implies rolling resistance will take 30*168.6 = 5058 Wh/mi!. Rolling resistance alone would deplete a 135 kWh charge in 27 miles.

Wh/mi are clearly the natural units for any computation of this sort so i suppose we would say that anyone wishing to do computations of this sort would naturally prefer wh/mi.

A lot of us like to keep track of how we are doing in our driving, understand why we did better or worse on a particular drive etc. Again Wh/mi are the natural units for the kinds of computations we do. Logging programs such as TeslaFI report Wh/mi etc and people who think about such things think in Wh/mi. We would of course prefer that the car displayed in Wh/mi but then we would, as someone else mentioned, prefer that the US used the metric system.

 

[ajdelange]

It came to me overnight that we can estimate a, b and c for the polynomial pretty simply as smart phones seem to all contain accelerometers these days. Get your car up to speed on on a level smooth bit of road, start your accelerometer recording an pop the vehicle into neutral. Use the data from the accelerometer with the model acc = (a + b*v + c*v*v)/m (you'll need to record v(t) as well as acc(t) in Excel and use the solver to estimate a, b and c. Using the formula in my last post you can WAG the rolling resistance component and the rest will be mostly drag. Measure the frontal area to guess Cd from drag.

 

[Speedrye]

I noticed some of the reviewers saying all 4 wheels regen, but the EPA docs only list the front wheels. While that makes sense in conserve mode, the EPA docs don't mention anything differently for sport mode. Just an oversight, or is regen only on the front wheels?

If it's on all four wheels, what type of clutches engage the rear motors, and could those be actively turned on and off so that the rear motors are used for regen in conserve mode, and then disengaged again when under power? No idea if the hardware could handle that constant engagement/disengagement or not.

 

[BigE]

Just the range hit on the cold weather. I live at under 20F for a good three to four months of the year. I expected a hit, but not 40%. Guess I should have done more research

My brother drives a Model Y and lives just north of Minneapolis. He keeps his Y in the garage and pre-conditions before heading out. Last winter he sent me pictures of the Y maintaining 72 degrees inside the car while at the grocery store and it was -20 F outside. The Y does have a heat pump, but that really only helps in mild temps, not sub-zero. You may want to play with A Better Route Planner and map some of your frequent trips. You can set your model and also make changes to energy consumption, etc. I'm from WI but now live in NC so I understand your situation. That being said, my R1T is configured as a Max Pack from the beginning. I tend to buy new and keep auto's ~10 years, so I just think for the long term, towing our camper, etc. Max pack is the way to go. I've tried to talk myself into the Large pack to save $$, but for me, 135 kwh in a 7,000 lb vehicle is just not enough at this point in battery development.

Follow-up: In talking with my brother this morning he said in Minnesota when temps are below zero Fahrenheit he expects about a 1/3 reduction in range on his Y.

 

[OldGoat]

It will be interesting to see how the reality of EV's starts to set in and impact the euphoria of all the excitement of these recent reviews, especially for those that don't have expereince with EV's. I suspect some will decide it isn't for them.

We have had our etron for a little over a year and it has been a real learning experience, trying to get comfortable with all the variables impacting range. For example, we took it up to the mountains and it ate ~ 160 miles getting there and ~40 miles getting back (uphill, vs downhill). I can assure all those that are new to EV's, range anxiety is real. It will take awhile before you get comfortable. You will, but unlike an ICE where you look at the gas gauge when you start the car and that's about it, the range gauge on the EV is mesmerizing, taunting you as it clicks down in seemingly unpredictable ways.

 

[ajdelange]

..clicks down in seemingly unpredictable ways.

Thing is it is quite predictable and the art of BEV driving lies in knowing how to predict it.

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