can you force no drive-battery charging while driving?

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STS134 said:
What I do is I simply use Save mode on the freeway, and Normal mode or EV mode around town. It's not an efficient use of battery power to cruise on the freeway, as in addition to causing a very high DoD, it also drains the battery at a rather high C rate http://batteryuniversity.com/learn/article/what_is_the_c_rate which is also hard on the it. Driving at a continuous 65-75 mph consumes about 20-30 kW, which is quite a bit of sustained power draw for a small 12 kWh battery. It also generates a lot of heat (and although we do have a battery cooling system, it's still hard on the battery to discharge it so much so quickly).
It appears to me that you do not fully understand what Save mode is. You must have noticed that even in Save mode the engine turns off regularly?

In Normal mode, there is a hysteresis cycle (engine on / engine off) during which the SoC goes up and down between roughly 30 (the low water mark) and 32% (the high water mark). During the engine off part of the cycle, power consumption is, like you said, about 30 kW and DoD is about 2%. In Save mode, the exact same thing happens. Same power consumption, same DoD. The only difference is that the low water mark is not at roughly 30% but depends on the actual SoC when you selected Save mode.


STS134 said:
Meanwhile, the ICE is reasonably efficient at sustained cruise. That's why I got a PHEV. Let the ICE do what it does best (freeway driving), and let the battery do what it does best (around town driving).
An ICE needs a decent relative load in order to be efficient. Just propelling the car does not provide such a load. And we cannot shift to a higher gear in order to increase the relative load. So, instead additional load is created by the generator. In other words, the ICE runs more efficiently when it is not just propelling the car but also charging the battery.

When a high SOC is maintained (above 65% real or 50% on the gauge), the maximum charge current is reduced to protect the battery. The higher the SoC, the lower the maximum charge current. This causes the ICE to drop out of the sweet spot and run less efficient. With a reduced charge current, it will take longer to increase the SoC by 2% (from low to high water mark) so the hysteresis cycle is impacted: the duty cycle (% of time with engine on) will be higher. So, over the same distance travelled, the ICE will have made many more revolutions and you will have spent more fuel overcoming internal resistance of the ICE itself.
 
Woodman411 said:
jaapv said:
Woefully underpowered? I drive regularly on the German Autobahn, plenty of hills and my average speed is about 150 kph. No lack of power at all. Just keep the charge button down, 120 kW from the electric motors and another 30 from the ICE will keep you going nicely.

I'm sorry, I took it too far. I meant trash panda power :) Autobahn, 150 kph, hills, "no lack of power at all"... Anyone like to back that up? My BMW X1 sdrive28i struggles at 130 kph on hills, and that's signficantly lighter than the Outlander phev. Lack of power is almost universal with online reviews:

https://www.wheels.ca/car-reviews/review-2018-mitsubishi-outlander-phev "sluggish performance"
http://www.nydailynews.com/autos/latest-reviews/flash-drive-2018-mitsubishi-outlander-plug-in-hybrid-review-article-1.3785887 "What’s the crux of the issue? Lackluster performance... highway passing and uphill slogs easily overtasked the drivetrain – and that's with only a pair of people aboard"
http://www.hybridcars.com/2018-mitsubishi-outlander-phev-first-drive-review "ask the vehicle to pass, surge up a hill, or merge with highway traffic, and suddenly you find yourself searching for the afterburner button"
https://www.caranddriver.com/reviews/2018-mitsubishi-outlander-phev-test-review "isn't quick by any means"

Outlander phev has many strengths, but got the impression power isn't one of them.

Definitely the Outlander PHEV is a boring car for German Autobahn ...

Yes .. there are most of the time 120kw of power, sometime a bit more at higher speed ... as well power could be less when ICE is cold or speed is low ...
Still 120kw for 1.8 tons car is not much, especially since it has a massive profile and lot of energy lost at high speed due to air resistance.

On top the PHEV does only 170km/h (restriction by design) which for Autobahn standards can be relative slow

For cross Germany I prefer to use my old BMW 335i tuned with 400HP .. then it makes more interesting to cruise there .. interesting enough .. at 130km/h and above, the BMW consume less fuel then the Outlander (main difference is SUV vs Coupe)
I also had in the past a BMW X1 x18d ... which was relative slow for my feeling (but still a more agile and reactive car compared to my Outlander, even if on paper the BMW X1 was having less power then our PHEV) ... my previous BMW 320d (with a little tune) was quite fast and it was consuming almost nothing and it had only 169HP (with a cheap chip tune to maybe 190HP)

Anyhow ... the Outlander PHEV is a car mainly designed for daily commute .. with the option to tow , make a bit of off road, etc ... so a quite versatile car, with lot of cabin space ... still not the best for take German Autobahns

PS: If you need more fan from an PHEV SUV ... I guess it is needed too look for a Volvo, Porsche or RangeRover ... but ... the cost of these are way more then the Mitsubishi, and I'm not sure they are better then the Outlander in EV mode or in the economy of daily commute ... as far as I know .. the Outlander is the only PHEV with 4x4/AWD in pure EV mode ...

PPS: One of the influence in the speed/acceleration factor ... is the engine noise ... we are used to ear the engine to rev up on standard ICE cars ... in the Outlander when we accelerate "hard" the engine jump immediately at high rpm, and then it does not change the sound .. so psychologically we don't hear the acceleration
 
elm70 said:
.. interesting enough .. at 130km/h and above, the BMW consume less fuel then the Outlander (main difference is SUV vs Coupe)
Coincidentally, 130 km/h is about the speed at which the PHEV can no longer drive in EV mode. So, 130 km/h is about the speed at which the hysteresis cycle is terminated. This means the PHEV is no longer a hybrid vehicle when driving 130 km/h or faster. Charge current is reduced to 0. ICE drops out of sweet spot. Down the drain goes the efficiency .... more or less ;-)
 
anko said:
STS134 said:
What I do is I simply use Save mode on the freeway, and Normal mode or EV mode around town. It's not an efficient use of battery power to cruise on the freeway, as in addition to causing a very high DoD, it also drains the battery at a rather high C rate http://batteryuniversity.com/learn/article/what_is_the_c_rate which is also hard on the it. Driving at a continuous 65-75 mph consumes about 20-30 kW, which is quite a bit of sustained power draw for a small 12 kWh battery. It also generates a lot of heat (and although we do have a battery cooling system, it's still hard on the battery to discharge it so much so quickly).
It appears to me that you do not fully understand what Save mode is. You must have noticed that even in Save mode the engine turns off regularly?

In Normal mode, there is a hysteresis cycle (engine on / engine off) during which the SoC goes up and down between roughly 30 (the low water mark) and 32% (the high water mark). During the engine off part of the cycle, power consumption is, like you said, about 30 kW and DoD is about 2%. In Save mode, the exact same thing happens. Same power consumption, same DoD. The only difference is that the low water mark is not at roughly 30% but depends on the actual SoC when you selected Save mode.


STS134 said:
Meanwhile, the ICE is reasonably efficient at sustained cruise. That's why I got a PHEV. Let the ICE do what it does best (freeway driving), and let the battery do what it does best (around town driving).
An ICE needs a decent relative load in order to be efficient. Just propelling the car does not provide such a load. And we cannot shift to a higher gear in order to increase the relative load. So, instead additional load is created by the generator. In other words, the ICE runs more efficiently when it is not just propelling the car but also charging the battery.

When a high SOC is maintained (above 65% real or 50% on the gauge), the maximum charge current is reduced to protect the battery. The higher the SoC, the lower the maximum charge current. This causes the ICE to drop out of the sweet spot and run less efficient. With a reduced charge current, it will take longer to increase the SoC by 2% (from low to high water mark) so the hysteresis cycle is impacted: the duty cycle (% of time with engine on) will be higher. So, over the same distance travelled, the ICE will have made many more revolutions and you will have spent more fuel overcoming internal resistance of the ICE itself.

Yes - I used to drive a Volvo 245TurboR (only a few built, most Turbos were tamed down) that was limited to 250, in the past and a series of Jaguars. That taught me one thing: It is a stupid exercise to drive long distances in that style. You will arrived exhausted from the extreme concentration needed at such speeds and the time gains are marginal. Much better to drive with the flow, in the optimum average speed of 130 (many speed limits nowadays...) to 150, which is the sweet spot for the Outlander. Fortunately many German drivers have twigged to the fact as well, making traffic much smoother.
 
jaapv said:
Yes - I used to drive a Volvo 245TurboR (only a few built, most Turbos were tamed down) that was limited to 250, in the past and a series of Jaguars. That taught me one thing: It is a stupid exercise to drive long distances in that style. You will arrived exhausted from the extreme concentration needed at such speeds and the time gains are marginal. Much better to drive with the flow, in the optimum average speed of 130 (many speed limits nowadays...) to 150, which is the sweet spot for the Outlander. Fortunately many German drivers have twigged to the fact as well, making traffic much smoother.
Is this the right topic for this response?
 
jaapv said:
Yes - I used to drive a Volvo 245TurboR (only a few built, most Turbos were tamed down) that was limited to 250, in the past and a series of Jaguars. That taught me one thing: It is a stupid exercise to drive long distances in that style. You will arrived exhausted from the extreme concentration needed at such speeds and the time gains are marginal. Much better to drive with the flow, in the optimum average speed of 130 (many speed limits nowadays...) to 150, which is the sweet spot for the Outlander. Fortunately many German drivers have twigged to the fact as well, making traffic much smoother.

Comfortable speed ... is very subjective.

It is all about traffic, number of lines, and shape of the motorway

But, in general in Germany if there is no speed limit, the road allow to drive at high speed .. which in general is close to 250km/h which is the standard electronic speed limit in most of german cars

In my experience I can gain more then 1h driving at high speed, just a simple math .. driving at average 130km/h vs 200km/h ... 200km take 1h30min in first case, and 1h in second case .. so driving at 200km/h allow to win 30min time for each hour .. that is not little

Anyhow ... my comfort speed with BMW 320d, BMW 335i and Fiat Coupe LE (my 3 fast cars which I drove in Germany) ... is between 180km/h and 220km/h .. 180km/h is very relaxing speed .. 220km/h is very fine with low traffic ... but .. getting close to 250km/h is more demanding ... unless the motorway is straight and empty from traffic ...

Clearly weather condition need to be good (if not perfect)

PS: Fuel consumption at 200km/h it is not that bad either on the fast cars I have/had .. around 11L/100km (probably the 320d was even 10L or less)

PPS: The bigger stress factor on driving fast ... is to be careful on not missing any speed limit on the motorway ... I have seen places in Germany that from unlimited, it was going down to 80km/h only for few hundreds meters (sometime without any logical reason) ... it could be a challenge to explain to the police why car was flying at 220km/h when speed limit was 120 or 80km/h
 
anko said:
elm70 said:
.. interesting enough .. at 130km/h and above, the BMW consume less fuel then the Outlander (main difference is SUV vs Coupe)
Coincidentally, 130 km/h is about the speed at which the PHEV can no longer drive in EV mode. So, 130 km/h is about the speed at which the hysteresis cycle is terminated. This means the PHEV is no longer a hybrid vehicle when driving 130 km/h or faster. Charge current is reduced to 0. ICE drops out of sweet spot. Down the drain goes the efficiency .... more or less ;-)

Not really at any speed it is possible to press the CHARGE button ... and some extra load is added to the ICE , so in theory the ICE is running more efficiently .. and the main battery get charged while driving in 100% ICE mode.

Clearly it is needed to have an ending part of the trip at a speed usable in pure EV mode .. else it is a waste to produce electricity from fuel instead of using electricity from the network .
 
anko said:
jaapv said:
Yes - I used to drive a Volvo 245TurboR (only a few built, most Turbos were tamed down) that was limited to 250, in the past and a series of Jaguars. That taught me one thing: It is a stupid exercise to drive long distances in that style. You will arrived exhausted from the extreme concentration needed at such speeds and the time gains are marginal. Much better to drive with the flow, in the optimum average speed of 130 (many speed limits nowadays...) to 150, which is the sweet spot for the Outlander. Fortunately many German drivers have twigged to the fact as well, making traffic much smoother.
Is this the right topic for this response?
Why not? it is about efficiency, charging and speed demand, isn't it?
 
elm70 said:
anko said:
elm70 said:
.. interesting enough .. at 130km/h and above, the BMW consume less fuel then the Outlander (main difference is SUV vs Coupe)
Coincidentally, 130 km/h is about the speed at which the PHEV can no longer drive in EV mode. So, 130 km/h is about the speed at which the hysteresis cycle is terminated. This means the PHEV is no longer a hybrid vehicle when driving 130 km/h or faster. Charge current is reduced to 0. ICE drops out of sweet spot. Down the drain goes the efficiency .... more or less ;-)

Not really at any speed it is possible to press the CHARGE button ... and some extra load is added to the ICE , so in theory the ICE is running more efficiently .. and the main battery get charged while driving in 100% ICE mode.

Clearly it is needed to have an ending part of the trip at a speed usable in pure EV mode .. else it is a waste to produce electricity from fuel instead of using electricity from the network .
Agreed, by using Charge mode, load can be added and charging can take place, even above 130 km/h. As long as your battery is not full. Some would call that hybrid, I guess.
 
Higher speeds may save time on the motorway, but it trashes fuel consumption, meaning you have to stop way more often. At higher speeds, aerodynamic drag is the major factor, and this varies by the cube of the speed. So increasing your speed from 100km/h to 110km/h increases the drag by 33% and affects your fuel consumption accordingly.

CAR magazine did a trip down Australia in a Porsche Turbo when the road didn't have a speed limit for much of the way. Despite trying to "max" the car several times and running at high speeds, their frequent fuel stops meant that a standard car (Honda Accord, I think) kept overtaking them at petrol stations.
 
anko said:
It appears to me that you do not fully understand what Save mode is. You must have noticed that even in Save mode the engine turns off regularly?

In Normal mode, there is a hysteresis cycle (engine on / engine off) during which the SoC goes up and down between roughly 30 (the low water mark) and 32% (the high water mark). During the engine off part of the cycle, power consumption is, like you said, about 30 kW and DoD is about 2%. In Save mode, the exact same thing happens. Same power consumption, same DoD. The only difference is that the low water mark is not at roughly 30% but depends on the actual SoC when you selected Save mode.
Yes, I understand exactly what Save mode does. It simply does the same thing as Normal mode does, after the battery reaches 1 bar, except it maintains the SoC at a higher level than 1 bar. That's what I want to do. It avoids essentially having to deep cycle the battery just because I'm driving on the freeway. And when cruising near 75 mph, it's taking about 20-30 kW from the battery as well, which generates a lot of heat (since the amount of heat generated is something like quadratic in relation to the power), and even though we have a battery cooling system, it's not a good use of battery power to be doing this if I can just use the ICE instead.

anko said:
An ICE needs a decent relative load in order to be efficient. Just propelling the car does not provide such a load. And we cannot shift to a higher gear in order to increase the relative load. So, instead additional load is created by the generator. In other words, the ICE runs more efficiently when it is not just propelling the car but also charging the battery.
Sure. But the ICE rarely turns off when I am on the freeway. It typically runs continuously unless I have to interrupt my travel (some car cuts me off for example). And a lot of the time, I go over 125 km/h and the ICE would have turned on anyway, regardless of mode.

anko said:
When a high SOC is maintained (above 65% real or 50% on the gauge), the maximum charge current is reduced to protect the battery. The higher the SoC, the lower the maximum charge current. This causes the ICE to drop out of the sweet spot and run less efficient. With a reduced charge current, it will take longer to increase the SoC by 2% (from low to high water mark) so the hysteresis cycle is impacted: the duty cycle (% of time with engine on) will be higher. So, over the same distance travelled, the ICE will have made many more revolutions and you will have spent more fuel overcoming internal resistance of the ICE itself.
You're forgetting one important thing: that round trips through the battery cause about a 20% loss of energy. So instead of doing round trips through the battery when driving around town, it's way better to use the ICE to just generate the power and consume it immediately, whether in series hybrid mode, or in parallel mode where it's sending mechanical power from the ICE directly to the wheels. Either way, the losses are closer to 0% than 20%. And then I have plenty of battery power left when I exit the freeway and the ICE can turn off and stay off.
 
ThudnBlundr said:
Higher speeds may save time on the motorway, but it trashes fuel consumption, meaning you have to stop way more often. At higher speeds, aerodynamic drag is the major factor, and this varies by the cube of the speed. So increasing your speed from 100km/h to 110km/h increases the drag by 33% and affects your fuel consumption accordingly.

CAR magazine did a trip down Australia in a Porsche Turbo when the road didn't have a speed limit for much of the way. Despite trying to "max" the car several times and running at high speeds, their frequent fuel stops meant that a standard car (Honda Accord, I think) kept overtaking them at petrol stations.
I find that hard to believe. On Interstate 5 in California, I will typically get up to 90-105 mph and hold it there all the way through the San Joaquin Valley. In my previous car, this caused fuel economy to fall from around 37 mpg to below 30 mpg. But I still gained A LOT in time. Even if you assume that I have to make an extra stop to fill up the tank, driving at that speed easily cuts at least 30-60 minutes off the journey, if not more. Does it take 30+ minutes to fill a gas tank? Yeah, I thought so.
 
ThudnBlundr said:
Higher speeds may save time on the motorway, but it trashes fuel consumption, meaning you have to stop way more often. At higher speeds, aerodynamic drag is the major factor, and this varies by the cube of the speed. So increasing your speed from 100km/h to 110km/h increases the drag by 33% and affects your fuel consumption accordingly.
Fuel consumption * per hour * wil indeed increase with the cube of increase of speed. So, 1.1 * 1.1 * 1.1. But fuel consumption per kilometer or per mile only increases with the square of increase of speed. So 1.1 * 1.1 = 1.21.
 
STS134 said:
And when cruising near 75 mph, it's taking about 20-30 kW from the battery as well, which generates a lot of heat (since the amount of heat generated is something like quadratic in relation to the power), and even though we have a battery cooling system, it's not a good use of battery power to be doing this if I can just use the ICE instead.
Sorry, I thought you said you used Save mode to prevent the 20 - 30 kW power drain. And that would not have worked.

STS134 said:
anko said:
An ICE needs a decent relative load in order to be efficient. Just propelling the car does not provide such a load. And we cannot shift to a higher gear in order to increase the relative load. So, instead additional load is created by the generator. In other words, the ICE runs more efficiently when it is not just propelling the car but also charging the battery.
Sure. But the ICE rarely turns off when I am on the freeway. It typically runs continuously unless I have to interrupt my travel (some car cuts me off for example). And a lot of the time, I go over 125 km/h and the ICE would have turned on anyway, regardless of mode.
Indeed, going over 125 km/h, the ICE run all the time (as EV drive is no longer available). At the same time, charging will stop. Presumably because the car knows it cannot use the built up charge at that speed, so it does not make sense to build it up. So, if you do not want to use the battery at freeway speeds, driving faster than 125 is the way to go, not Save mode :D

But, like I said, also driving around at very high SOC will cause the ICE to run a larger percentage of time. Because the charge current is reduced, it takes longer to up the SoC with 2%.

STS134 said:
anko said:
So, over the same distance travelled, the ICE will have made many more revolutions and you will have spent more fuel overcoming internal resistance of the ICE itself.
You're forgetting one important thing: that round trips through the battery cause about a 20% loss of energy. So instead of doing round trips through the battery when driving around town, it's way better to use the ICE to just generate the power and consume it immediately, whether in series hybrid mode, or in parallel mode where it's sending mechanical power from the ICE directly to the wheels. Either way, the losses are closer to 0% than 20%. And then I have plenty of battery power left when I exit the freeway and the ICE can turn off and stay off.
I am not forgetting this. I am also not forgetting the power needed to crank up the ICE over and over again. But I am also not forgetting the fact that Mitsubishi made an effort to implement a hysteresis cycle. I cannot imagine they would have done that if the hysteresis cycle was less efficient than pure ICE operation. They cannot be that stupid :lol:

Maybe you are underestimating the efficiency increase of the ICE or overestimating the losses associated with the battery trips?
 
anko said:
Sorry, I thought you said you used Save mode to prevent the 20 - 30 kW power drain. And that would not have worked.
Well yeah, it *does* prevent 20-30 kW from leaving the battery. It prevents the battery from having to entirely supply that load. Since the ICE is running and is turning the generator, the motors are using the generated power instead of the battery power.

anko said:
Indeed, going over 125 km/h, the ICE run all the time (as EV drive is no longer available). At the same time, charging will stop. Presumably because the car knows it cannot use the built up charge at that speed, so it does not make sense to build it up. So, if you do not want to use the battery at freeway speeds, driving faster than 125 is the way to go, not Save mode :D
Well, sort of. My speed fluctuates, and sometimes goes under 125 km/h. In Normal mode, the vehicle would revert to EV driving until the battery is nearly exhausted. That's what I want to avoid.

anko said:
I am not forgetting this. I am also not forgetting the power needed to crank up the ICE over and over again. But I am also not forgetting the fact that Mitsubishi made an effort to implement a hysteresis cycle. I cannot imagine they would have done that if the hysteresis cycle was less efficient than pure ICE operation. They cannot be that stupid :lol:
It's not surprising. This is exactly how Toyota manages the batteries on its HEVs. And that's also why their HEV batteries last a LONG time. They keep them at around 60-70% SoC nearly at all times, and the only significant deviations from that level are when climbing steep hills or when descending steep hills. But they basically behave like our PHEVs with Save mode set at 60-70% SoC.
 
STS134 said:
Well, sort of. My speed fluctuates, and sometimes goes under 125 km/h. In Normal mode, the vehicle would revert to EV driving until the battery is nearly exhausted. That's what I want to avoid.
Okay, I see what you mean. But driving slower for longer periods of time with Save mode would not prevent EV mode from occurring. Driving faster for longer periods of time without Save mode would prevent EV mode from occurring. So, is it speed or Save mode that prevents EV mode? Also, if you allowed the battery to drain normally, to its normal low water mark, would the ICE not also keep running when you dropped below 125? Like we agreed, Save and Normal mode are exactly the same except for the position of the low water mark.

The DoD story is a different thing, of course. But I have never heard that hovering around 30% would be much worse than hovering around 60%. At least, not if you plan on fully draining the battery eventually, before reaching the next charge point anyway.

STS134 said:
It's not surprising. This is exactly how Toyota manages the batteries on its HEVs. And that's also why their HEV batteries last a LONG time. They keep them at around 60-70% SoC nearly at all times, and the only significant deviations from that level are when climbing steep hills or when descending steep hills. But they basically behave like our PHEVs with Save mode set at 60-70% SoC.
I think you cannot compare a HEV with a PHEV. Because, what an HEV does not have is a relatively cheap supply of grid power that you want to use up before you get home.
 
anko said:
Okay, I see what you mean. But driving slower for longer periods of time with Save mode would not prevent EV mode from occurring. Driving faster for longer periods of time without Save mode would prevent EV mode from occurring. So, is it speed or Save mode that prevents EV mode? Also, if you allowed the battery to drain normally, to its normal low water mark, would the ICE not also keep running when you dropped below 125? Like we agreed, Save and Normal mode are exactly the same except for the position of the low water mark.

The DoD story is a different thing, of course. But I have never heard that hovering around 30% would be much worse than hovering around 60%. At least, not if you plan on fully draining the battery eventually, before reaching the next charge point anyway.
Sure, *if* you are going to drain the battery to the point of needing the engine to come on, it probably doesn't matter too much (although I would it's still better to use the ICE on the freeway, because draining the battery on the freeway does it at a higher average power level and generates a lot more internal heat). But here's an example. My commute is about 16 miles, and 2/3 of that is freeway. So the idea here is that by going into Save mode, I prevent the battery from going into a high DoD at all. Typically, I can use only about 20-35% of the battery on my 16 mile commute (instead of 50-65% of it). And then I recharge at work. We've seen the effect of DoD on battery life (Table 2 on this page): http://batteryuniversity.com/index.php/learn/article/how_to_prolong_lithium_based_batteries.

The thing is, hovering at 30% isn't that much worse than hovering at 60%. But doing, say, 80% to 30% every day compared to 80% to 55% every day is going to kill your battery a lot faster. About four times as fast actually (you get double the number of CYCLES with half of the DoD, in other words, going from 100% to 50% twice as often as going from 100% to 0% means the battery lasts twice as long. But I'm not merely talking about doing half of the DoD twice as often per day, I'm talking about doing half of the DoD the same number of times per day, so we expect the battery to last 4 times as long, because it's only being used half as much, and the DoD factor doubles its life on top of that) Now if you compare 55% to 30% vs. 80% to 55%, that's where there's not much difference. The absolute SoC doesn't really matter too much, as long as it's below about 4.05V/cell, but the depth of discharge matters a lot.

anko said:
I think you cannot compare a HEV with a PHEV. Because, what an HEV does not have is a relatively cheap supply of grid power that you want to use up before you get home.
Sure, but I guess what I'm trying to say is that PHEV batteries are by far the most abused. PHEV batteries have usage patterns that tend to make batteries die very quickly.

HEVs have the benefit of holding the batteries at a pretty good SoC the vast majority of the time, and even though the instantaneous C rates at which they are charge and discharged are high, this typically does not last very long.

BEVs have very high capacities relative to daily driving. Think a 300+ mile Tesla or a 230 mile Bolt. How many miles does the thing get driven per day? Probably a lot fewer than the capacity of the battery, and hence, DoD is low. Because of this, many BEVs have a feature that allows the user to tell them to only charge to 80% or so, and to only go to the maximum that the BMU will allow before long trips. Also, because BEVs have such large batteries, they go through not too many cycles over their lifetimes. For a BEV with a 300 mile range battery, 100000 miles is only 333.3 cycles.

PHEV drivers on the other hand really tend to beat up their batteries. Because the batteries are smaller than those for BEVs, they not only discharge at high C rates for extended periods of time (like at 2C for if driving on the freeway in our Outlanders using 24 kW without using Save mode, while the huge size of the batteries in BEVs mean that even using 24 kW, you are only discharging the 100 kWh battery in a Tesla P100, for example, at 0.24C.), but they also are barely enough to supply power for our daily drives, and many times, not enough. Therefore, a lot of people drain the batteries to the maximum allowed, then charge them up to full, every single day, and sometimes multiple times per day. The BMU obviously tries to protect the batteries by only allowing discharge to 30% and stopping charging at around 85%, but there's really only so much you can do with a usage pattern like that. So by using Save mode on the freeway, I'm also trying to manage degradation in a way that preserves my battery for the long term. Yes, it's probably a little more expensive to use the ICE on the freeway compared with using electricity, but that neglects the cost of the battery itself. As a critical drivetrain component, as well as an expensive component to replace, I'd rather preserve it to do what it does best (powering the car on surface streets), and use the ICE during times it's reasonably efficient to do so. If you calculate the cost of battery replacement from allowing a high DoD every day, I suspect that the calculations would show that it's not worth it to burn electricity on the freeway.
 
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