Toyota RAV4 Forums banner

EV mode is wasteful / less efficient on the highway - Misconception

10388 62
I've heard people in a number of places talk about driving in EV mode around town or whatever and then when getting on the highway, putting it in HV mode because EV mode is less efficient on the highway, or should I say at highway speed. I don't get this logic and I think it is based on a misconception, but I'd love to hear other thoughts...

Yes, ev mode on the highway is less efficient than it is around town. The same goes for HV mode. The faster you drive, the more drag the vehicle has to contend with, and it is non-linear meaning doubling your speed requires much more than double the power to overcome the increase in drag. The source of power that moves the vehicle forward has nothing to do with this. You will get fewer EV miles on the highway than around town in most cases, but the same goes for HV miles. If you have a 100 mile trip, 50mi on the highway and 50 miles driving ~40mph off of the highway, you're going to use roughly the same amount of (combined) electricity and gas no matter how you split up the EV/HV driving.

The only exception I see here is that if the engine is running, you're not consuming extra energy to heat the cabin since you can use waste heat for that from the heater core.

Now I do still believe that AUTO EV/HV can be worth running on the highway for longer trips. This allows the car to pull less current from the battery by using the engine to assist under high loads, which is better for the battery and requires less use of the a/c to cool the battery.
1 - 20 of 63 Posts

·
Registered
Joined
·
81 Posts
I've heard people in a number of places talk about driving in EV mode around town or whatever and then when getting on the highway, putting it in HV mode because EV mode is less efficient on the highway, or should I say at highway speed. I don't get this logic and I think it is based on a misconception, but I'd love to hear other thoughts...

Yes, ev mode on the highway is less efficient than it is around town. The same goes for HV mode. The faster you drive, the more drag the vehicle has to contend with, and it is non-linear meaning doubling your speed requires much more than double the power to overcome the increase in drag. The source of power that moves the vehicle forward has nothing to do with this. You will get fewer EV miles on the highway than around town in most cases, but the same goes for HV miles. If you have a 100 mile trip, 50mi on the highway and 50 miles driving ~40mph off of the highway, you're going to use roughly the same amount of (combined) electricity and gas no matter how you split up the EV/HV driving.

The only exception I see here is that if the engine is running, you're not consuming extra energy to heat the cabin since you can use waste heat for that from the heater core.

Now I do still believe that AUTO EV/HV can be worth running on the highway for longer trips. This allows the car to pull less current from the battery by using the engine to assist under high loads, which is better for the battery and requires less use of the a/c to cool the battery.
I would not say that EV is ever less efficient at any time. But with a limited amount of EV (battery availability), I run the ICE on the highway because it is more efficient at highway speeds relative to stop and go in town traffic. If you have more than enough battery capacity for your entire trip then I would run EV for the full duration. My understanding is that AUTO EV/HV gives preference to EV and quickly depletes the battery. I never use that mode. I’ll select either EV or HV manually depending upon trip length and driving conditions.
 

·
Registered
Joined
·
62 Posts
It’s actually pretty simple. The 42 miles estimated from EV applies to low average speeds. If your average speed is 70+ then you might only get 30 miles on a charge. If you travel all low speeds, you might get 50 miles on a charge.

The efficiency is the same for gasoline, the faster you travel, the lower mpg you get.
 

·
Registered
Joined
·
30 Posts
Discussion Starter · #4 · (Edited)
I would not say that EV is ever less efficient at any time. But with a limited amount of EV (battery availability), I run the ICE on the highway because it is more efficient at highway speeds relative to stop and go in town traffic. If you have more than enough battery capacity for your entire trip then I would run EV for the full duration. My understanding is that AUTO EV/HV gives preference to EV and quickly depletes the battery. I never use that mode. I’ll select either EV or HV manually depending upon trip length and driving conditions.
ICE in a hybrid setup, just like with an EV, is generally more efficient in stop and go and city driving than at highway speeds. Non-hybrid ICE powertrains are more efficient on the highway than in stop and go. AUTO EV/HV does give preference to the battery but uses the engine in cases where more power is needed, which seems to make sense.

It’s actually pretty simple. The 42 miles estimated from EV applies to low average speeds. If your average speed is 70+ then you might only get 30 miles on a charge. If you travel all low speeds, you might get 50 miles on a charge.

The efficiency is the same for gasoline, the faster you travel, the lower mpg you get.
Agree totally, what seems off to me is the idea that switching between ev/hv depending on highway or regular roads makes some kind of sense. If you're taking a trip that is long enough to deplete batteries, I think the amount of gas you use will be roughly the same no matter when you use ev/hv. If you're taking a trip that won't deplete the battery, I see no reason to use hv mode unless you're in situations where you will encounter high engine/powertrain load, in which case auto ev/hv seems like your best bet.
 

·
Registered
Joined
·
62 Posts
ICE in a hybrid setup, just like with an EV, is generally more efficient in stop and go and city driving than at highway speeds. Non-hybrid ICE powertrains are more efficient on the highway than in stop and go. AUTO EV/HV does give preference to the battery but uses the engine in cases where more power is needed, which seems to make sense.



Agree totally, what seems off to me is the idea that switching between ev/hv depending on highway or regular roads makes some kind of sense. If you're taking a trip that is long enough to deplete batteries, I think the amount of gas you use will be roughly the same no matter when you use ev/hv. If you're taking a trip that won't deplete the battery, I see no reason to use hv mode unless you're in situations where you will encounter high engine/powertrain load, in which case auto ev/hv seems like your best bet.
But... that’s exactly the point.

I’ll save my EV battery to use it around town stopped at a stop light. More efficient.
Running the engine while stopped at the stop light because I drained my battery on the highway. Not efficient.
 

·
Registered
Joined
·
30 Posts
Discussion Starter · #6 ·
But... that’s exactly the point.

I’ll save my EV battery to use it around town stopped at a stop light. More efficient.
Running the engine while stopped at the stop light because I drained my battery on the highway. Not efficient.
In HV mode, when stopped, the engine is off except for in cases where the engine is still warming up, in which case it is charging the battery.
 

·
Registered
Toyota RAV-4 2013
Joined
·
44 Posts
I believe this is true Only if you have some charge remaining, once I ran out completely and engine would run continuously in city traffic.
Were you trying to heat the cabin at that point? I haven't run my RAV completely out of "EV" range yet but I have had the engine run continuously in extreme cold to provide cabin heat. I drove a regular hybrid RAV4 and it shut off the gas engine while stopped, like it should.
 

·
Registered
Joined
·
1,337 Posts
Electric for me is half Dino Juice

We just filled our Prime gas tank after 6 months ownership.

I drive to work 56 miles round trip 70 - 85 mph in EV and cold days 2.0 -2.2 miles per kWh

Lately with temps in the upper 40’s low 50’s I have been hitting 2.6-2.7 miles per kWh.

Last Aug when we purchased the Prime I consistently hit 2.8 per kWh and I drive fast

Around town driving 30 mph I can get 3.2 miles per kWh.

I have nothing to compare but 2.7 miles per kWh is $1.31 to travel 39 miles compare to gasoline the same distance I am half the cost Dino juice.
 

·
Registered
2021 RAV4 Prime SE; 2022 XC60 T8 ER
Joined
·
465 Posts
HV mode makes sense when you're driving outside of your battery range and driving > 40-45 mph. EV makes sense when you're driving < 40 mph, while you're driving within the range of your battery. Auto-EV/HV makes little sense at any time, because it runs in hybrid mode but runs the battery down very quickly; it might make sense if your drive between charging is like 50-100 miles, but makes no sense if your distance is > 100 miles. HV essentially runs in hybrid the most efficiently, keeping the battery at about the same charge level, when driving long distances. Yes, the air drag on a car increases exponentially as your velocity gets higher and higher, but because we have very limited energy through our 18-kWh battery pack (compared to our 14.5-gallon gas tank), the electric driving takes a big hit much more quickly at high speeds, and ICEs tend to be much less efficient than electric motors in slow, stop-and-go traffic. So drive in all-electric at slower speeds, and drive in hybrid (HV) mode at faster speeds. You don't have to touch any buttons on a long road trip, and the car will just go into "Auto-EV/HV" mode once your battery is drained (which will be very quickly on a long road trip). I will routinely use EV mode at up to ca. 83 mph on the expressway locally when driving short distances, within my EV range, simply because its much more enjoyable to drive in electric mode than with the ICE on (at any time), even if that drains the battery much faster -- but that's just me. If I have to drive 40 miles on expressway, I'll just put it in HV mode when I get to highway speed and then pop back to EV mode when slowing down again; this way I almost always have plenty of battery for that stop-and-go slow traffic.
 

·
Registered
Joined
·
738 Posts
I feel like I have to defend Auto-EV/HV. It gives you the full power of the car, and yet you can tool around mostly in electric mode. Imagine that the RAV4 was a sports car. It would make a lot more sense. 302 hp at every traffic light and stop sign. And yet quite and serene gliding along the rest of the time. I agree it's not that useful to most of the present owners. But I think that's becasue we are not the right market segment. Also, if you think about it, Auto-EV/HV is really just a few lines of code. It's not like there is a ton of expensive hardware.
 

·
Registered
Joined
·
1,337 Posts
If you drive less than 40 miles EV which in my case is 90% of my driving.

If I know my trip will be more than 40 miles I just run the EV dry and let her switch to HV and enjoy 35 -37 mpg freeway driving.

Wind and outside temperature , I have found knocks my EV range.

The heat pump draws 30 amps and until things warm up my range is 1.6 miles per kWh.

After the heat pump has warmed things up after a few miles the range settles in around 2.2 miles per kWh if it is cold outside but when temps are above 60 F I easily get 2.7 miles or 39 miles of range driving 70 mph
 

·
Registered
Joined
·
30 Posts
Discussion Starter · #13 ·
HV mode makes sense when you're driving outside of your battery range and driving > 40-45 mph. EV makes sense when you're driving < 40 mph, while you're driving within the range of your battery. Auto-EV/HV makes little sense at any time, because it runs in hybrid mode but runs the battery down very quickly; it might make sense if your drive between charging is like 50-100 miles, but makes no sense if your distance is > 100 miles. HV essentially runs in hybrid the most efficiently, keeping the battery at about the same charge level, when driving long distances. Yes, the air drag on a car increases exponentially as your velocity gets higher and higher, but because we have very limited energy through our 18-kWh battery pack (compared to our 14.5-gallon gas tank), the electric driving takes a big hit much more quickly at high speeds, and ICEs tend to be much less efficient than electric motors in slow, stop-and-go traffic. So drive in all-electric at slower speeds, and drive in hybrid (HV) mode at faster speeds. You don't have to touch any buttons on a long road trip, and the car will just go into "Auto-EV/HV" mode once your battery is drained (which will be very quickly on a long road trip). I will routinely use EV mode at up to ca. 83 mph on the expressway locally when driving short distances, within my EV range, simply because its much more enjoyable to drive in electric mode than with the ICE on (at any time), even if that drains the battery much faster -- but that's just me. If I have to drive 40 miles on expressway, I'll just put it in HV mode when I get to highway speed and then pop back to EV mode when slowing down again; this way I almost always have plenty of battery for that stop-and-go slow traffic.
I'm a bit confused by this, I'd think HV mode makes sense when you're out of battery power or want all 300hp, otherwise EV mode makes sense. Auto-EV/HV does not "run in hybrid mode". It runs in ev mode but uses the engine occasionally when more power is needed, i.e. you give it a lot of gas or you're driving fast up a steep hill. It lets the powertrain computer decide when it is best to add engine power. ICE engines only have this inefficiency in stop-and-go traffic when they are configured in non-hybrid powertrains. As a hybrid, the engine is not less efficient in stop and go traffic...

You can't be in auto ev/hv mode when the battery is drained, when you run the battery down you are automatically put into HV mode.
 

·
Registered
2021 RAV4 Prime SE; 2022 XC60 T8 ER
Joined
·
465 Posts
I'm a bit confused by this, I'd think HV mode makes sense when you're out of battery power or want all 300hp, otherwise EV mode makes sense. Auto-EV/HV does not "run in hybrid mode". It runs in ev mode but uses the engine occasionally when more power is needed, i.e. you give it a lot of gas or you're driving fast up a steep hill. It lets the powertrain computer decide when it is best to add engine power. ICE engines only have this inefficiency in stop-and-go traffic when they are configured in non-hybrid powertrains. As a hybrid, the engine is not less efficient in stop and go traffic...

You can't be in auto ev/hv mode when the battery is drained, when you run the battery down you are automatically put into HV mode.
No, HV mode makes sense when you're on long highway drives, because it conserves the battery charge (more-or-less) while still allowing hybrid driving (with an emphasis on the ICE). I think that you may be correct about "Auto EV/HV" mode; I just never see a need to use it. Quite frankly, the electric motors alone accelerate enough for me to safely get on any expressway from on on-ramp, but if I need more, I'll switch it over to HV or (easier, because you don't have to look) I'll turn the mode dial to Sport. Our daily driving is such that we rarely need to use the ICE, so just stay in EV mode all the time. It's that one-or-twice-amonth that we drive a longer trip where we go outside our 45-mile EV range and will put it into HV mode to keep plenty of battery available for slow-downs on congested expressways or for the local driving when we get off. If you use "Auto EV/HV" on longer trips, it'll drain your battery really fast, and you won't have all the electric that you want when going slower later. As an owner of three Porsches over the years, I smile when I read people here liking to drive the RAV4 Prime in a sporty mode; for me, all the fun is when the ICE is off, not when it's on. :) (and P.S.: I'm not a slow driver :giggle:)
 

·
Registered
Joined
·
298 Posts
Another reason it's worthwhile to save EV for city driving is that EV mode will prevent the engine from turning on as much. Most city driving is stop and go, and sometimes leaving the car for 5+ minutes to run errands. If you can reduce the total number of warm ups the engine experiences, you're going to gain a lot of efficiency.
 

·
Registered
Joined
·
30 Posts
Discussion Starter · #17 ·
No, HV mode makes sense when you're on long highway drives, because it conserves the battery charge (more-or-less) while still allowing hybrid driving (with an emphasis on the ICE). I think that you may be correct about "Auto EV/HV" mode; I just never see a need to use it. Quite frankly, the electric motors alone accelerate enough for me to safely get on any expressway from on on-ramp, but if I need more, I'll switch it over to HV or (easier, because you don't have to look) I'll turn the mode dial to Sport. Our daily driving is such that we rarely need to use the ICE, so just stay in EV mode all the time. It's that one-or-twice-amonth that we drive a longer trip where we go outside our 45-mile EV range and will put it into HV mode to keep plenty of battery available for slow-downs on congested expressways or for the local driving when we get off. If you use "Auto EV/HV" on longer trips, it'll drain your battery really fast, and you won't have all the electric that you want when going slower later. As an owner of three Porsches over the years, I smile when I read people here liking to drive the RAV4 Prime in a sporty mode; for me, all the fun is when the ICE is off, not when it's on. :) (and P.S.: I'm not a slow driver :giggle:)
I suppose I don't see a reason to conserve battery charge on the highway, if you're on a long trip and will need to use the gas engine, and since it's a hybrid system with a gas engine, it's also less efficient on the highway than it is in the city since it regularly turns off in the city and charges the battery when not propelling the car. I like auto ev/hv on long trips because, as stated in the owner's manual, "avoiding driving in ev mode at high speeds or under hard acceleration will help prolong battery longevity" (paraphrased). In auto ev/hv mode, when in a situation that would normally put a high load on the battery, the engine kicks in to help out a bit, which is better for the battery.

Another reason it's worthwhile to save EV for city driving is that EV mode will prevent the engine from turning on as much. Most city driving is stop and go, and sometimes leaving the car for 5+ minutes to run errands. If you can reduce the total number of warm ups the engine experiences, you're going to gain a lot of efficiency.
It takes the engine a long time to cool down to a point where it really has to warm up again, much longer than 5 minutes even in the cold.
 

·
Registered
Joined
·
395 Posts
I suppose I don't see a reason to conserve battery charge on the highway, if you're on a long trip and will need to use the gas engine, and since it's a hybrid system with a gas engine, it's also less efficient on the highway than it is in the city since it regularly turns off in the city and charges the battery when not propelling the car. I like auto ev/hv on long trips because, as stated in the owner's manual, "avoiding driving in ev mode at high speeds or under hard acceleration will help prolong battery longevity" (paraphrased). In auto ev/hv mode, when in a situation that would normally put a high load on the battery, the engine kicks in to help out a bit, which is better for the battery.



It takes the engine a long time to cool down to a point where it really has to warm up again, much longer than 5 minutes even in the cold.
Sounds like good logic to me!
 

·
Registered
Joined
·
47 Posts
Has anyone measured/documented battery temperature while driving in EV at high speeds (freeway-up long hills)? There is a limited number of battery cells and the speed(stress) placed upon these limited number of cells may cause temperature increases beyond what one really wants for longevity purposes.
 

·
Registered
2021 Rav4 Prime XSE Pro Audio/Dynamic Nav/Weather Packages Build date: June 2021
Joined
·
1,115 Posts
Has anyone measured/documented battery temperature while driving in EV at high speeds (freeway-up long hills)? There is a limited number of battery cells and the speed(stress) placed upon these limited number of cells may cause temperature increases beyond what one really wants for longevity purposes.
I don't see this as an issue, using EV mode for freeway speeds at least in the 65-70mph range. It takes huge input of energy to accelerate to 65mph (compared to 0-30mph, about 4x more to go from 30 to 65mph), but maintaining that 65-70mph doesn't require all that much input--just observe the power meter on the left side of the display--it's typically right in the middle of the Eco range, at least on the relative level.
 
1 - 20 of 63 Posts
Top