I had no idea the efficient fell off a cliff when it's raining!

[Tcoma]

Hi all, long time lurker shopping a number of vehicles now. We finally rented a '23 MY LR on Turo for local driving and a short road trip. I will be posting soon with pics and many thoughts and questions, but I've got to get this off my chest first: Holy crap does rain do a number on the mileage! Is this normal??

Our road trip was between Indy and NWI so the trip was almost entirely on I-65, a 70mph mostly 4 lane interstate. We charged up to 90% (as per the owner) and hit the road. We're just testing it out, and I'm no longer an impatient teen, so I set the cruise control for (gasp!) only 72 and luckily got behind a semi truck that barely changed lanes and apparently used his cruise control. The distance between vehicles setting was at 3, so I was close enough, but hardly drafting. It was a fairly enjoyable drive, and the road was thankfully not too busy. We hit a supercharger very close to the end of our trip which reported 231 Wh/mi for 162 miles on a sunny spring day in the upper 50s, lower 60s. In retrospect, I should have waited the extra 10 min or so to get up to 90% at the SC, but we capped off at 80% since everyone was anxious to get to Easter dinner.

We left at night after it started raining, and I didn't pay much attention to the charge at first since I "calculated" that we had enough juice to get home, but certainly to get to any of the SCs along the way. I saw there was at least one in Lafayette, which is sort of in the middle of our route. I could easily make it there. We drove most of the way in the rain, and we skipped the first SC option, although the car suggested we stop. Yes I realize that was a mistake, but again, considering my inexperience and the Wh/mi we got on the way there, I assumed we'd get something similar on the way back. About 20-30 min past that SC, I noticed that the estimated mileage was decreasing at about twice the rate we were accruing them. But we had plenty of battery to get to Lafayette. The car was not routing us to that location though. My wife looked it up and discovered only hotel options, so we assumed it was for guests only? Why else wouldn't the car route us there? It routed us further away.

The rain really started coming down, and we started to get nervous. Actually, I got confused, and my wife started to get a little panicky. We shut off all possible battery draws, but the battery continued to deplete precipitously, getting into the 390s for usage. What is going on here? I don't know how mpg changes in our Palisade driving in the rain - if at all - but I'm quite certain it doesn't increase gas consumption by 70%. I'm no dummy, but as I said, this was our first EV experience. It matched estimates with actual mileage almost perfectly for the previous couple days, and on the ride there. I couldn't believe that it was just a matter of rain that utterly wrecked the Wh/mi.

Needless to say, we squeaked into an SC with I think 6% left. I charged up to 45% or so, and that was about 3.5x what we should have needed to get home. Coincidentally, it stopped raining just in time for me to plug in. We left and stayed in the right lane, dutifully behind semis doing under the posted car speed limit. We got home with about 100 miles left in the e-tank, having averaged 245 Wh/mi for the remaining time on the road.

Now keep in mind that I'm filtering all this info through the lens of a 40 year history of ICE cars without as much as a hybrid in the mix, much less an EV. I did a fair amount of research before (and now after) our scare last night, and found little info about the efficiency during the rain. Not that it isn't out there, but I would have assumed that big of a hit to efficiency would have been "front page news" but I never heard of it until I specifically looked it up, and even then there isn't much said about it.

Is this normal? If so, how can the car correctly plan road trips with the unknown of weather absolutely ruining the fuel consumption rate?

(other than that, the car has been an absolute blast, but that review is for another post. The Y was probably #1 on our replacement vehicle list after we sell the Palisade, but this definitely knocked it down a few notches behind PHEVs and hybrids in my wife's mind. I need to get after some damage control if I think this is going to be our next family car.)

 

[boones]

Could the efficiency hit also have been due to wind? Your consumption of 231Wh/mi is very low compared to my averages. Maybe you had a tailwind on the way there and a headwind on the way back? I recently returned from a 2400 mile road trip in my 23 Y and we had a day of driving directly into 40-50 mph winds. That killed range by like 50% compared to normal. The trip was in TX with 75 mph limits and prevailing traffic speeds higher than that, so even without wind average consumption was 340Wh/mi.

 

[ucmndd]

Wind and heavy rain can absolutely tank your efficiency by a LOT. It did the same in your ICE car too.

 

[Jonez]

Well, live and learn, going on a trip, just like ICE you top it off 100% not 90 NEVER 90 your going on a trip. You are driving the most technology advanced passenger vehicle in the world. Probably a good idea to give it a drink of electrons when it asks for them. By doing this the car will condition the battery for the fastest possible charge. You can plan your trip online so you know what to expect. It is just an experience thing you get used to it. Always use the navigation too as the elevation changes and temperature are factored it.

 

[jkdman123]

70% decrease in efficiency sounds high, but yes, rain can have a dramatic effect. Yes, rain can affect ICE cars but I don't think it's nearly the same.

I had kind of the same thing happen to me going from San Diego to LA and back. It started raining on the way back. It took 40% to go from home to LA starting at 100%, so I figured I may not even need to charge, since theoretically I should get home at 20%. After about 30-40 mins of driving I realized there was no way I was gonna make it home at the rate I'm going. I thought it might have been to range inaccuracy or something having to do with battery management, but later realized the only real diff was the rain.

 

[dafish]

wind is the big thing, (and as you can see often not understood) then speed, then hvac demand. Rain? Minor impact in my experience. Arriving at 6%? Well done. I plan on 10-15%. You want to be low to SC because it’s much faster. And this BS about always charging to 100%? Utter nonsense. Charge to what you need ONLY and get back on the road. This as charge speed drops above 50%, decreases as you go, and becomes substantially less by 80%.

Personally I trip plan for 3 miles per kw and plan to arrive with a 10% reserve. i use 2.5 miles below freezing. I adjust speed or draft if I’m burning through my planned rate. usually I draft.

Btw, drafting a semi works well in these, even back 2-3. Can make a very big difference. Sort of like catching a tail wind.

You’ll learn quickly, take a few more trips.

 

[brkaus]

Rain in the roadway is pretty big, but will depend on the amount of water and the road surface.

 

[dafish]

Ah, heavy rain. I have to fess up I’ve not logged usage in a really major and extended downpour. Typical rain showers, etc? Nbd

 

[GHammer]

... going on a trip, just like ICE you top it off 100% not 90 NEVER 90 your going on a trip.

In over 300,000 miles of road tripping, in all lower 48, with over 2500 supercharger sessions, I never charge to 100%, heck I rarely go over 70%. Charging to 100% just wastes time.

 

[holmgang]

If its raining it might be windy too. A 10mph headwind wind is as if you were cruising at 82mph instead of 72mph.

If that was true, in the detailed energy card it would have told you very specifically “wind from [direction] cost/saved you x%”, along with other consumption information.

Next time just listen to the computer.

 

[Jonez]

In over 300,000 miles of road tripping, in all lower 48, with over 2500 supercharger sessions, I never charge to 100%, heck I rarely go over 70%. Charging to 100% just wastes time.

at a SC ill agree the time from 70 to 100 is longer than say 20 to 70%, about 15 minutes, but if you are leaving on a trip say in the morning why not charge to 100 overnight, if you have anxiety about charging miles then the 15 minutes you spend extra may be worth it mentally. In the end it is up you and your style of driving, and experience, obviously your a pro but for newbies.....

 

[FastEddieB]

Airplanes suffer a definite hit to airspeed in the rain. It increases surface friction drag by disturbing the laminar flow of air over the wings. Of course, in a car this is compounded by the drag of the tires meeting the water puddling on the road surface.

 

[Tcoma]

Wow - thanks everyone for all the great input. I appreciate the handholding for the ICE minded like myself, i.e., people who think of EVs in terms of ICE dynamics. I don't know, maybe it's like the last great major transportation change - people who thought of ICE cars in terms of horse and carriages?
¯\_( ツ)_/¯

Further reading helped elucidate the effects of rain on efficiency by way of some pretty basic math: if so much of the energy released during ICE car driving is converted to heat, and not motion -- in other words, the inefficiency as it pertains to driving -- then environmental issues such as rain would have a relatively smaller effect, to the point of even being unnoticable in normal driving. Please bear with me if this is all well understood; I'm just sounding it out for myself to make sure I understand it. Feel free to correct my thought process. Numbers I've seen indicate an efficiency (% of energy converted to motion in this case) somewhere in the 20% range for ICE cars, but more like 90% for EVs. Therefore, environmental factors (changing friction of one form or another, like air or rain) presumably have the same effect on the moving vehicle regardless of power source. But - since only 20% of the ICE energy is devoted to the miles traveled, then a given hit to the motion efficiency should overall be only a hit to 20% of the MPG, if I understand correctly. Again, if this is true, it would be fair to say that -- eliminating all other factors -- a car that gets 30 MPG on a given route at a given speed in the dry, would get [30 x 0.2 x (increased friction factor)] + (30 x 0.8). Ok, so arbitrarily saying that there is an efficiency/friction reduction of 50% due to the rain's increase in amount of friction, the formula would go something like:

30 x 0.2 x 0.5 + 30 x 0.8 or 27 mpg.

But an EV that gets 100mpge (or whatever measurement of distance per unit of fuel) would be affected more like:

100 x 0.9 x 0.5 + 100 x 0.1 or 55 mpge.

Obviously there can be many more additional factors contributing, but my goal as a lifelong data nerd is to understand the basic trend first. The above seems to apply in the case of 2 vehicles with the same coefficient of drag and the same tires, although with differing methods of converting the energy source into motion.

Again feel free to critique the above or if I'm right just enjoy the feeling of watching a child grasping how to tie his shoes for the first time.

 

[brkaus]

@Tcoma this is exactly my understanding. I tried to type it out several times but never felt my wording made sense.

 

[Johnny Vector]

at a SC ill agree the time from 70 to 100 is longer than say 20 to 70%, about 15 minutes, but if you are leaving on a trip say in the morning why not charge to 100 overnight, if you have anxiety about charging miles then the 15 minutes you spend extra may be worth it mentally. In the end it is up you and your style of driving, and experience, obviously your a pro but for newbies.....

Because you lose regen braking (not such a big deal now that you can turn on automatic blended braking, but still), and unless your trip is all on that first charge, or there are only V2 chargers along the route*, it makes almost no difference in the total trip time. On a V3 charger, the time from 10% to 20% (the extra time you have to spend because you started at 90% instead of 100%) is between 2 and 3 minutes. In most cases you’ll never notice that in the overall trip.

I plan to charge to 100% at my hotel outside the path of totality so I can get to the planned state park for the eclipse and then back to the hotel with plenty to spare (cause there are no Superchargers in that 100 mile stretch). Otherwise, I never go above 90% even before a big trip.

*Or you’re towing, or a few other specific and uncommon cases, yes yes.

 

[Tcoma]

Could the efficiency hit also have been due to wind? Your consumption of 231Wh/mi is very low compared to my averages. Maybe you had a tailwind on the way there and a headwind on the way back? I recently returned from a 2400 mile road trip in my 23 Y and we had a day of driving directly into 40-50 mph winds. That killed range by like 50% compared to normal. The trip was in TX with 75 mph limits and prevailing traffic speeds higher than that, so even without wind average consumption was 340Wh/mi.

I tried to take a pic of the appropriate data whenever I plugged in. The "avg. energy since last charge" numbers I recorded were: 242, 228, 231, then the dreaded 390 in the rain, 339 after a stop to look through the map, 349 to the SC in Lebanon IN, then 245 for the rest of the trip home. Then 222 for a local drive and 265 on an admittedly hotdoggin' race back to return the car in time. Big fun in busy, high speed interstate traffic. See a spot in traffic ahead? No problem, just point and shoot; you're there.

But anyway, my concern remains. Well, at least my wife's (and thus mine): how does the route planner take weather into account? Is there a connection to a weather station or something? Sounds kind of fantastical I know, but with Tesla, who knows!

 

[brkaus]

The trip planner does a reasonable job, but does need someone looking over it. As there are more and more charging locations (including ccs ones) it becomes less of an issue.

One time I drove from Austin to Dallas (220 miles) and thought I was headed from Kansas to Oz. 20-30+ mph headwind. Had to stop 3 times because each time the planner and I underestimated. But that’s one of 100s of trips.

Usually I can target arrival at 10% or so and modulate that with the go pedal (speed) as the trip proceeds. Knowing the number of fall back chargers on a particular route can be helpful if surprises come up.

And if I feel like I know better, I set the destination and remove charging stops.

Worst case, a tow to a charger or a standard wall outlet for a long time. But never came close for me.