Hybrid Mode

If that was the case I think Prius Prime owners all over the world would be screaming.
HV mode basically runs like the traditional version of the Prius.
In that case (other than driver error) the Traction battery would not run down except in
rare situations like LONG uphill runs where the ICE can't handle the load itself and
depletes the battery before reaching the top of the hill. In that case you need to slow
down or pull over and let the ICE replenish the battery enough to continue but those
situations are rare. Plus you get a good portion of that back on the flipflop portion
of the trip during the downhill coast/regen.

 

What is your electricity cost?
What is your gasoline cost?

Thanks,
Bob Wilson

 

I can answer the opposite of that question: My brother drove his Prime until the battery fell out of EV mode then filled it up and drove to Lewiston, ID. (From Bellingham, WA) Getting home again he had used 7 gallons of gas (56 MPG) and now had 12 miles of EV charge from coming down the North Cascades highway.

So it can recharge the EV part of the battery in HV mode.

 

I have found it difficult to get confirmation on this, but my understanding is that in your example of climbing a hill in HV mode it will only use the HV portion of the traction battery, combined with ICE of course. If the HV charge gets depleted before you reach the top of the hill then you are on ICE alone, even if you have capacity available in the EV portion of the battery it will not use it. As you described this could mean that you may not be able to safely or at least easily continue up the hill in HV mode depending on how steep it is because ICE will be the only source of power with no assistance from the electric motor. As you said just like a regular Prius in that scenario. Of course you could switch to EV Auto mode at that time (assuming you have EV range available) and the car will then start using the EV portion of the battery, and if the hill is that steep it will probably kick on ICE as well. In fact even in regular EV mode it could turn on ICE in that situation.

Downhill is a little different because regen comes into play. From what I understand in HV mode ICE is never used to charge the EV portion of the battery, ICE will only charge the HV portion of the battery. However regen will charge the EV portion of the battery even in HV mode. Back to the scenario where you are in HV mode climbing the hill, and the HV portion of the battery is depleted, and either you remain in HV mode on purpose or you are out of EV range, so you complete the climb on ICE alone. When you crest the hill, on the downhill regen will first recharge the HV portion of the battery, then when the HV portion is "full" then regen will start charging the EV portion of the battery. Although I think I remember someone saying that in HV mode regen won't charge as much of the EV portion of the battery at it does in EV mode, but I don't know if they were right. Either way, whatever capacity is put back in the EV portion of the battery during regen will only be available the next time you are in EV mode, that capacity will not be available while driving in HV mode.

Anyway that's what I have been able to gather from various Prime owner's comments, unless someone has experienced something different.

 

I'm no authority but from reading and on multiple test drives I've come to the following deductions:

1) The first 20% of battery charge is for HV use. Anything over 20% is available for EV use. EV
usage will not invade the first 20% of the battery charge.
2) In HV mode (not EV auto) the battery will not charge above 20 % by the ICE with the exception of
regenerative power recapture (which really isn't the ICE doing it).

Ergo, to get the battery charged above 20% you need to plug it in or do some serious regenerative
capture (downhill coasting etc.) or put the car in "Charge Mode".

None of the dealers in my area with Prime's available for a test drive plug them in and every one
I've driven the battery charge level has been almost exactly at 20% when I start the test. The only
way I could get the charge above 20% was to use "Charge Mode". Here in the midwest aka flatland
there are few hills to test downhill regeneration.

These are my observations and won't feel bad if proven wrong.

J

 

Just a tiny nit to pick; No Prius charges the HV battery in N, so by 'coasting' you mean in D or B when going downhill. (I can't imagine anyone charges much in R)

 

HV portion & EV portion of the battery??? Huh?

Even if no charge is showing on the display, the battery has some. It'll use that when it wants to. Toyota has kept some secrets from us.

Just drive it. The system is smart. Plug it in when you can.

Drive safely.
Drive courteously.
Drive efficiently.

 

Correct no charging in N or R.

 

Sure that's the nice thing is that you can just drive it and still get great MPG. But I'm not sure if you are telling people who are interested in getting even better MPG to forget it? Some people like figuring out how to get a few extra miles per gallon (or kWh) just by making some minor adjustments to their driving or by pushing a mode button at certain points in their journey. But if that's not your cup of tea that's perfectly fine.

But for those who are interested there seems to be some reliable strategies for improving the already great efficiency, because although the system is pretty smart it doesn't know when you are about to get on the freeway, or when you are about to go uphill (or downhill) or how much farther you will go before charging, etc. etc. One day I'm sure hybrid systems will communicate with the Nav system and know all of that, probably around the same time that they figure out how to get the Nav clock synchronized with the dash clock But until then the driver knows some things the system doesn't and can make choices that can improve efficiency. But only if they first understand how the system works. Which is what this discussion is about.

For everyone else, drive on!

 

There are several incorrect statements in the paragraph quoted above, Since2002.


First, I'll answer the OP's question, which was "if I drive in hybrid mode all the time with the traction battery fully charged, will the hybrid mode eventually drain the traction battery? Or does the hybrid mode only use the blue part of the battery? ", because it will help point those statements out (and make you feel way more confident than you are, Since2002, in the way the Prius operates)


To answer the OP's question...
1) There's just one battery, and there is no "EV portion". There is no "blue part of the battery" - that's just a visual indication of when the battery level is lower than the amount that the Prius computers have determined would allow for less than 0.1 miles of EV only operation.

2) One is *never* on ICE alone in a Prius Prime. One is *never* on ICE alone in any Prius. Ever. And the battery *never* runs out. Yes, *never* runs out. I'll say it a third time - The traction battery will never get drained. The car won't let it happen. The ICE can't physically turn the wheels in a Prius without one of the electric motors (MG1) applying force against the sun gear in the power split device (MG2). Therefore, answering the original question, if one drives in hybrid mode all the time with the traction battery fully charged, the hybrid mode will never fully drain the traction battery.

3) Have you ever put your Prime in "HV Mode" when, say, there are 20 miles of EV range left? Notice how the Prius lets the battery fluctuate in a range between, say, 18 and 22 miles of range left, with the car magically re-centering it to around 20 miles of range left over time? Well, when the EV range goes from 0.1 miles left to none (looks like --.- miles left on the display), it does the exact same thing -- it is fluctuating in a range centered on the amount just under "0.1 miles of EV left" -- with the "little EV"

Now, moving on to Since2002's thoughts about going up hills:
The scenario you're thinking of where the EV miles run out while someone is going up a hill, and immediately the engine is using ICE only (stated by you as "If the HV charge gets depleted before you reach the top of the hill then you are on ICE alone") is false. See 2) above. What you're really observing, in my opinion, is a driver going up a hill in EV mode, with the engine never having been on during a drive, and the EV-only miles drop from, say, 25, down to 0.1, and then from 0.1 down to "--.-". At that moment, the Prime's ICE is going through its "engine warm-up cycle", where it is focused on heating itself up to minimize emissions -- and it's not actually driving the car for the first minute or so while it focuses on warming itself up***. That feeling of "oh, no, the battery is gone" that you have is really quite the opposite - it's the battery continuing to push your car up that hill until the engine is warmed up.

So, therefore, Since2002 - you can put your mind at rest: If the Prius is able to travel up a hill in EV mode, it will safely continue to let you travel up that hill when your EV miles run out, and will continue to do so until you run out of gas. And it will *never* run out of battery (though you won't be able to drive it once you run out of gas )

Now, as to some of your comments about downhill - I'll copy your quote, and add my comments in bold
"From what I understand in HV mode ICE is never used to charge the EV portion of the battery, ICE will only charge the HV portion of the battery." -Incorrect - there is only one battery, and there are no separate "portions". The ICE will charge it with its excess engine capacity when it is efficient to do so. The Prime also has a mode called CHG mode (engaged by pushing and holding the HV/EV button) which will more aggressively let the ICE charge the battery - all the way up to the point from "no EV miles left" to "around 20 EV miles left" - just like regen does on a huge downhill.

However regen will charge the EV portion of the battery even in HV mode. Regen will charge the battery. There is no "EV portion"

Back to the scenario where you are in HV mode climbing the hill, and the HV portion of the battery is depleted, and either you remain in HV mode on purpose or you are out of EV range, so you complete the climb on ICE alone. When you crest the hill, on the downhill regen will first recharge the HV portion of the battery, then when the HV portion is "full" then regen will start charging the EV portion of the battery. You're just seeing the effect of additional energy being put into that single battery. Although I think I remember someone saying that in HV mode regen won't charge as much of the EV portion of the battery at it does in EV mode, but I don't know if they were right. They were not right. Either way, whatever capacity is put back in the EV portion of the battery during regen will only be available the next time you are in EV mode, that capacity will not be available while driving in HV mode. Not true - in HV mode, the car will use that extra battery charge from the regen from the last downhill portion.

Since2002 - I'm *not* trying to pick on you - hopefully that will help with your quest to help you guide your car when you stated "But until then the driver knows some things the system doesn't and can make choices that can improve efficiency. But only if they first understand how the system works. Which is what this discussion is about."


***The Prime doesn't do that good of a job showing you the warm-up cycle when it has -.-- miles of EV range left, but you can see it happen if you turn on HV mode with, say, 20 miles of EV range left -- you'll notice for the first minute or two that the EV range goes down to, say, 18 miles while the engine is on -- that's because the engine is focusing on heating itself up, and not driving the car. Eventually, the engine will be warmed up, and it will use excess engine capacity (along with re-gen from the brakes, etc.) to re-charge the battery up to 20 miles of range when it is efficient to do so if you continue to drive in HV mode.

 

The two points that seem to be the bulk of your reply are already so well known and discussed here so many times that I didn't bother to mention them again, although based on your reply I guess I should have. So I will clarify those points here, then reply to your comments in a separate message.

The traction battery never goes empty - Yes we all know that, maybe not the OP so I probably should have mentioned it again, that for battery life the system does not let the capacity drop below a certain percentage. Assuming that is what you are referring to. It just complicates every discussion to keep mentioning all the time that when someone says "run out" of EV range that they mean run out of what the system will allow you to use. But for the rest of my post I will state it so that it is not unclear.

There is only one traction battery - well the OP seemed to understand that, at least I assumed that from their statement about the "blue part of the battery" that they were referring to what I have heard many times that although there is only one physical traction battery, the software considers a certain amount of charge as being available for use in HV mode and the other "portion" as it is sometimes referred to as being available only for EV use. The evidence for that idea I assume being that people have learned that they can switch to HV mode and preserve their EV range for later use. Of course physically it's all just one big available charge, just like you have a certain amount of money in a bank account but via the ATM you can only access a portion of it on any one day, say $300. It's not like the bank has physically set aside $300 in currency with your name on it, rather it's all about accounting, which essentially is what the "division" of the traction battery represents. Or perhaps a better example is a partitioned hard drive, that's all done in the OS as logical drives, it's not like half of the disk is physically set aside for a particular drive letter. And yet from the users point of view it behaves as if they were separate physical drives which can be accessed independently.

Charge mode - a separate mode that doesn't factor into a discussion about what happens in HV or EV mode which is why I didn't bring it up.

 

So back to the uphill scenario, if prior to reaching the hill you have already depleted the EV range (i.e. the amount of charge that the system will allow you to use in EV mode) it will have already switched to HV mode and run the warmup cycle even before you get to the hill. If you then start up a long hill climb at a relatively high power demand (i.e. driving a normal speed not crawling, and maybe doing some passing) then it will use both gas and battery charge at whatever rate is needed to provide this power. The system has no idea if this is a mountain pass or just a freeway overpass, so it will give you the power that you are requesting. However if this continues for any length of time it will eventually deplete whatever is left of the amount of battery power that the system will allow you to use. Maybe when that level is approaching it will first reduce the rate of battery discharge, which I haven't heard it does but I could imagine it might as a way of extending things a bit further. Which of course would be perceived by the driver as a reduction in available power. But even at a reduced discharge rate if you keep it up it will eventually run out of the amount of battery charge that the system will allow you to use. Maybe that is rare, especially for people in geographic areas that don't have long hill climbs. But when it does happen then only the ICE will be available to climb the hill.

However you say this is wrong, that "One is *never* on ICE alone in a Prius Prime". If that is true then what happens in the scenario that I describe above, if you have already used all of the battery charge that the system will allow you to use, where can it get power to continue the uphill climb other than ICE?

As for battery "portion" you say that this is wrong there is no such thing it's all one happy battery, and that the system treats it as one battery. If that is what you are saying then is different than what I have repeatedly heard. Although as I mentioned I have not been able to get it confirmed. I will add yours to the opinions that I have been listening to, although you are the first that I can remember saying it doesn't work that way. But that doesn't mean that you aren't correct.

 

if it used up the wall charge in hv mode, what would ev auto mode be for?

 

I have a Scangauge on my Prime. The SOC(state of charge) gets down to about 12-13% before it kicks it out of EV mode to hybrid mode/ ICE. Maximum charge gets up to 82% when plugged in.

EV auto or EV mode will not come on when the battery is used up. It will only run in hybrid mode.

 

ev auto just allows the ICE to kick on to supply extra power when needed. in EV only mode, even when floored, the ice won't kick on while you have charge remaining.

 

While I take pleasure in manually controlling my Prime, I started to let the car drive it because it often drives more efficiently than I do hypermiling. This has been proven by my wife who just drives it obtaining better Eco scores and MPG figures in distances well beyond EV range (150-200) 75% hwy on mostly flat terrain. I also find the Prime better than I driving long decent. I set DRCC at a speed and just steer. We have an amazingly smart car.

Posted via the PriusChat mobile app.

 

i was not saying that it would. i was asking what use would ev auto mode be, if hv mode, when used with a full charge, used up the wall charge. isn't that what ev auto does? decide when to use ev and when to use hv until the wall charge is gone?

that is my understanding as well. so if hv mode used up the wall charge, wouldn't it be the same as ev auto?

 

EV Auto gives priority to EV, basically attempting if possible to run only EV, and only using ICE under heavy power demands like hard acceleration. Although people report that even in EV Auto mode ICE rarely comes on, if ever, probably depends on the driver. Whereas HV mode is like a regular hybrid and will use whatever combination of gas and electric is most efficient at the moment.

However the other part of your question "if hv mode used up the wall charge", if HV used up the wall charge then people would not be able to preserve EV charge for later use by switching to HV mode, and yet that is widely reported as working very effectively.

EDIT - of course clarifying again that inside the battery there isn't a sectioned-off area for "wall charge" but the system certainly knows how much of the traction battery's charge came from plugging in, and thus in the software it can essentially keep that amount of charge separate and not available in HV mode, which is what I have heard people say how it works. However breakfast says that is not the case that the system accesses the entire charge no matter what mode it's in.

If that is the case, HV obviously uses battery charge at a much lower rate than EV, so even if HV does use the so-called "EV charge" it will do so at a much lower rate, so in that sense you would still be preserving EV charge by running in HV as compared to running pure EV (or EV Auto). For relatively short periods, say fifteen miles cruising at freeway speeds it could give the illusion that the entire charge is being preserved, which could be why people say it works that way, when it fact EV charge is being used but at a lower rate. However that would only work for so long, on a longer highway trip the EV range would eventually be depleted, and yet I thought I have heard of people preserving EV on trips until they arrive at their destination so that they can use it for in town driving. Perhaps it all depends on the length of the trip and other driving conditions.