Let's talk about your Fall/Winter EV range drop

We live in Redding. We're getting about 33-34 lately

 

What was your previous plug in?

How cold is your mild cold weather?

 

It's all about the cabin heating usage (or mostly). Running with climate off will get a big chunk of the miles back, but not a great option if it is freezing inside the cabin. I tend to use the heated seats as much as I can and keep the cabin a little cooler than normal, but not too uncomfortable if I am trying to maximize range.

 

33% of the Prius Plug-in's range is about 4 miles, am I right? Did it have electric heat? I didn't think so.

 

That’s about what I’m seeing in Boston. My experience from last winter is that it doesn’t keep dropping even as we move into January, oddly.

I blame the winter tires, the battery itself, increase air density (really) as a matter of fact. Heat is probably the big one really as others have said.

A data point: to pre-heat the car when it’s been left outside at 30 deg pulls a total of 2.4 kWh from the charger. That would take a big bite out of the battery if I didn’t precondition. And of course when you’re driving the battery/heat has to keep up with ongoing heat losses to keep the cabin warm in a 50 mile an hour, 20° wind.





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The temperature here in Salt Lake City has been high about 42 and low about 22. I had a condition where I needed to drive the exact same route 2 days in a row so I decided to do a test of the electric heater.
The first day I drove with the heat and AC turned off using only the seat heater. I got 4.31 miles/KWh which I calculate relates to 56 miles of EV with a full charge.
The next day I drove with the heat set at 70 degrees and also used the seat heater. I got 3.01 miles/KWh or about 39 miles of EV with a full charge.
None of the driving was above 45 mph on flat ground.
My car is always charged in a semi conditioned garage where the temperature never exceeds 85 degrees in the summer and never below about 50 degrees in the winter.

Yes, the resistant heater uses a lot of power. I calculated a year ago that the heater will reduce your EV miles 1/10 mile every 20 seconds it's on or about 1 mile for every 5 minutes that it is on.

 

I agree completely with this. With a nominal rating of 47 miles. we get variations of roughly +/- 10 miles seasonally (36-40 in the winter, and as high as 55 in the summer). As Robert points out, I believe you lose roughly 10 miles just due to cabin heat, so that accounts for most of it. I tend to freeze myself in the winter in the name of 'conservation', but that is my own irrationality. My wife... not so much. She runs the heater. To each his own !

We are in Maryland. The car is in the garage so doesn't really experience full environmental exposure. Some of our friends in Canada get some very extreme conditions and report even greater losses. All perfectly normal.

 

My understanding is: The Prius plug in used the engine to warm engine coolant to provide heat. So the engine ran more often which in turn provides some charge to the battery. There was less impact to electric range but more engine use. The Clarity engine will not engage unless there is a low SOC, high power demand, or extreme low temperatures (<5F). The Clarity uses electric resistance heat to heat a heater core and will only use the engine to supplement in extreme cold.

Different approaches have different pros and cons. In a standard ICE vehicle when the engine is constantly running in a wasteful fashion constantly kicking off energy as heat that is not used for locomotion it is easy to take some of that waste heat and use it for cabin heating. In an efficient vehicle heat comes at a cost of either gas or electricity. Although even if you need to exercise your Clarity engine a little bit to help with range and heat in the cold weather your are still saving money and energy compared to a standard ICE vehicle. You are also probably doing your engine some good by running it once in a while.

If you want to have less range drop and simulate your Prius plug in just run in HV mode for part of the time you are using the heater. You will use some gas but have less range drop.

 

I was down into the 30s charge until i run to zero miles and then can charge back to 44. Wonder if programming charge zero to full is better than 20 to 40. ???

 

The above collective wisdom is spot on and tells you that you have nothing to be concerned about.
The reduction in range is primarily due to decreasing temperature having 2 main effects.

First, it causes you to use energy for cabin heating that would normally be a available for propulsion. Electrical resistance heating takes a lot of kWhs and will significantly reduce your range compared to using the ac in the summer. The metrics mentioned in the above posts are very helpful in calculating your reduced range on the fly. The best way to mitigate this “problem” inherent in all types of EVs is to precondition (helps increase range, but not energy usage), then use seat heat only or with as little cabin heat as possible (minimal reduction in range), or just freeze your you-konw-whats off (better range and efficiency, but loss of comfort and spousal happiness). The good news is that the ac is powerful, quick to blow cold air, and has a very small effect on range.

Second, it causes the battery to hold less energy and to use more energy per mile compared to warmer temperatures. While our Canadian friends get a battery heater, all we can do to mitigate this is to garage our Claritys. My unheated, insulated, attached on one side to house garage rarely gets less than 50 F in KY and never got below 42F during temps in the 20s with brief periods of single digits. (Currently at 57 F with temps in the 30s. This makes a big difference and was my much needed motivation to clean out the garage!

As a result, the first winter I had my Clarity, I was determined to see how efficiently and cheaply I could drive so I preconditioned and used only seat heat, gloves and heavy coat (local trips only). I never went below 49 miles indicated EV range and the garage never went below 42 F even when daytime temps were in the 20s and briefly down to single digits. This winter I will use cabin heat like the mere mortal I am. I am expecting my rage to go down to high 30s to low 40s. We shall see.
The reduction in range due to cold temps is the dirty little secret of EVs that is usually not included when talking about all their many benefits.
Even gas-mobiles get lower MPG in the winter although not as much as BEVs. So I’ve gotten over my desire to wring every last kWh out of my wonderful Clarity now that I have my treasured stats, I will now drive comfortably this winter. I am content with knowing that the Spring will bring back my stellar efficiency and that over the course of the 4 seasons I will still beat the EPA 47 mile EV range.

PS: I routinely get 4-5 miles less range actually than the EV estimated range.

 

Western Oregon has been kinda warm this winter -- daytimes in the 40's -- sometimes high 40's and overnights have been variable, some getting close to freezing but really not bad. In this weather, and not a lot of rain, my car's ev estimate is about 30 EV miles daily, sometimes up to 32.

Last year when it got cold, my EV range estimate dipped to 25.

 

As a footnote to this: preconditioning is one area where the L2 chargers should really shine vs the L1s. As I noted earlier, preconditioning on a cold day takes 2.4kWH. However, preconditioning shuts off (I think) after 30 min. An L2 charger can manage this in that time, though.

By comparison, in 30 min, an L1 charger (which at most is 1.5kw) can only pull a total of 0.75 kWh even ignoring losses, etc. Not enough to warm the car up fully-so you need to really plan ahead and re-precondition, or (more likely) just drive the car and heat it the rest of the way off the battery.




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I am in So Cal and getting 50+ miles per charge this month.

But then I don't use the cabin heater.

 

That is why its so much better than other PHEVs out there so far because even at 38 EV miles, most people will not have to use gas. A Prius PHEV of my friend's goes down to 18.

 

Mine has dropped about 20% I think, but I tend to only use the heater when I have windshield fogging issues. Aside from the heater usage there are a lot of things that can affect range in colder conditions, especially in the very cold climates: winters tend to be more windy than the other seasons; the colder and drier air is also more dense than warmer, humid air (thus more air resistance); winter tires are less efficient, and loss of air pressure in the colder days will raise rolling resistance; also those of us driving in snow/slush will have a lot more rolling resistance.

But another thing that I think plays a large role is that regen can be suppressed to a large degree when the EV battery is cold. You can see when L2 charging on cold days that the charging rate is decreased, since the cold Li-ion battery can only accept a limited charging rate. When I click on the regen paddles on cold days I sometimes feel the deceleration is very meager (both in feel and the limited deflection of the green regen needle gauge). Occasionally when using the brake pedal with constant force in winter I feel a lurch which I believe is the system accepting a high regen current and then suddenly deciding it is too much for the cold battery and then it swaps over to mainly friction brakes and during that transition I can feel a brief loss of braking power before it re-engages. It doesn't happen often, but when it has happened it was braking on cold days (not an ABS event).

Anyway, I think the loss of some regen drags the EV range down quite a bit on cold days. Just speculating based on one and a half winters of use.

 

After a bunch of time on these forums I finally figured out why my range is *always* lower. I live up about 1000' from the valley floor. Anyway, each trip up my hill kills a few (maybe up to 3-6) miles of EV range. So if I venture out an average of 3 times a day, my estimated EV range takes a hit for each return trip home (up the hill). Then I live in Oregon, so running a fan on the windshield is 100% required daily. We have high enough humidity and cold that trying to drive with defrost and windshield-fan off is unsafe six months of the year. Also with high humidity, our cold while maybe not much in measured degrees feels very cold, so more likely to hit the heat.

All that other stuff folks do to tune their experience counts too, but in my experience things like living up a hill or running the heater are the major factors. Then there's a lot of small factors that help or hurt too. i.e. driving relatively faster, or quick starts, take a hit on EV range, etc. But none of that is as potent as the car's heater and living up a hill.

I'm glad I got a car with rated 47 range, which is really like 25-30 half the year in my case. As I'm sure a car rated ~28 would become 14 for me in winter. But yeah, I may be a worst-case for the car, but yep, I really see 40-50% range reduction in winter, and the important part of what causes that cannot be eliminated in my case (i.e. not tune-able are my hill + "defrost"). Oh and yes, a member here told me how to run defrost without AC. It turns out I was already doing that without realizing it. i.e. while the advice is correct, it doesn't make my numbers go up in my case.

 

I lose close to 50% range in the winter.
Consider the cold months in New England as a survival test until we get to the Southern California climate in April here.