Battery Save Works Until You Stop...

[Kaboom]

Hi All,

Ever noticed this?
You've got a long motorway journey ahead. You press battery save with 20 drive battery miles left.
You do a bit of overtaking and the range comes down to 16miles - but before it can recharge back up to 20miles you stop at the services.
When you get back in the car you can only save 16 miles - not the 20 you wanted.

Is this the same for all the PHEV models or just the 3?

Thanks

 

[jaapv]

All models. When you switch the car off (or just the Save button) it will forget the level it was saving to. Not a problem, you can charge up to 20 and then switch on Save.
Note that the mile indicator does not correspond 1:1 with the state of charge, as it takes power consumption history into consideration. The SOC is of course indicated by the bar diagram.

 

[gwatpe]

There is a work around.

You can still lock the PHEV with the car powered ON.

When you stop and park at the service, leave the PHEV powered ON. push the central lock button on the drivers door. this will lock all the passenger doors. Exit via the drivers door and use the manual key to lock the drivers door. Car is locked, but not alarmed from my test. The SAVE value will be preserved for the remaining drive home.

I had used this method on occasions, but my power ON in SAVE mode mod has freed up my driving style and now I just turn "OFF" SAVE mode when I want to use some battery. You are obviously using petrol on your drive, so pure EV operation is not an essential criteria.

As has been mentioned prior, you can have a go to use CHARGE to match the km estimated to the actual km needed to be driven, but unless it is imperative to return on EV only, it seems too much trouble.

I would not consider it a problem to arrive home with even a few km of battery remaining, by preserving a little more battery before the SAVE was turned OFF.

This will only benefit drivers who will by necessity need to use the petrol during their journey.

 

[maby]

There is a work around.

...
I had used this method on occasions, but my power ON in SAVE mode mod has freed up my driving style and now I just turn "OFF" SAVE mode when I want to use some battery. You are obviously using petrol on your drive, so pure EV operation is not an essential criteria.

As has been mentioned prior, you can have a go to use CHARGE to match the km estimated to the actual km needed to be driven, but unless it is imperative to return on EV only, it seems too much trouble.

I would not consider it a problem to arrive home with even a few km of battery remaining, by preserving a little more battery before the SAVE was turned OFF.

This will only benefit drivers who will by necessity need to use the petrol during their journey.

Fully agree - and we got caught out by this over the weekend - I forgot to press Save and let the battery run far lower than I like to see it. I really wish they would give us a Sticky Save option - or better still a Sticky Prius Mode - which moves the charge floor level up to something around 50%. As soon as you go far beyond the battery range, the running costs becomes dominated by the petrol consumption and there is little value in trying to tune the battery usage but letting it go flat does impact on performance.

 

[jaapv]

I still cannot replicate this power loss with a "flat" battery . My car seems to be happy to play with its power reserve.

 

[maby]

I still cannot replicate this power loss with a "flat" battery . My car seems to be happy to play with its power reserve.

But you do agree that even with a well charged battery, it will start the engine in response to a significant demand for power - climbing hills or accelerating off the lights? For maximum performance, it wants both power sources - run out of petrol, or run out of charge and you are left short of power. If you drive the car gently (and I know that hills are rare in your part of the world!) then you may not notice, but if you use it as a general purpose car, exploiting its potential power, you will find the battery depleting and engine revving high in response to significant power demands.

 

[Ozukus]

I find the only time the ICE cuts in when fully charged is if I'm in the passeger seat, missus tends to have a lead foot :?

 

[maby]

I find the only time the ICE cuts in when fully charged is if I'm in the passeger seat, missus tends to have a lead foot :?

Nah! She's just driving it like a car, rather than a milk float. Driving with a fully charged battery in Normal mode, I reckon on getting about 90% EV on the gauge.

 

[jaapv]

I still cannot replicate this power loss with a "flat" battery . My car seems to be happy to play with its power reserve.

But you do agree that even with a well charged battery, it will start the engine in response to a significant demand for power - climbing hills or accelerating off the lights? For maximum performance, it wants both power sources - run out of petrol, or run out of charge and you are left short of power. If you drive the car gently (and I know that hills are rare in your part of the world!) then you may not notice, but if you use it as a general purpose car, exploiting its potential power, you will find the battery depleting and engine revving high in response to significant power demands.

Yes of course - overtaking, red light sprints (somewhat rare with me) Motorway work (long and heavy will call for charge, I should think), all will lead to the ICE cutting in. It does not bother me, and in all these cases I do not notice a significant difference in performance by the SOC. Mountains are different, I drive the Alps regularly, but then I will use Charge and not Save.

 

[maby]

I still cannot replicate this power loss with a "flat" battery . My car seems to be happy to play with its power reserve.

But you do agree that even with a well charged battery, it will start the engine in response to a significant demand for power - climbing hills or accelerating off the lights? For maximum performance, it wants both power sources - run out of petrol, or run out of charge and you are left short of power. If you drive the car gently (and I know that hills are rare in your part of the world!) then you may not notice, but if you use it as a general purpose car, exploiting its potential power, you will find the battery depleting and engine revving high in response to significant power demands.

Yes of course - overtaking, red light sprints (somewhat rare with me) Motorway work (long and heavy will call for charge, I should think), all will lead to the ICE cutting in. It does not bother me, and in all these cases I do not notice a significant difference in performance by the SOC. Mountains are different, I drive the Alps regularly, but then I will use Charge and not Save.

My ICE is running a lot of the time since I regularly drive well beyond the EV range. Since all but about 20 miles of my journey are going to be done on petrol anyway, I choose to drive on Save until I'm close to my destination so that I have plenty of reserve in the battery whenever I need the extra acceleration. I do admit that I often arrive home with charge left in the battery, but this really does not matter - if I've done over 200 miles over a long weekend and arrive back with five or ten miles of EV range left in the battery, the impact on my running costs is minimal. Monday to Thursday I'm generally doing less than 10 miles per day and these are done on pure EV.

 

[anko]

Mountains are different, I drive the Alps regularly, but then I will use Charge and not Save.

So would I. But how far do you have to drain the battery before you really notice any difference in behaviour / performance in these circumstances? I think you said, you didn't notice any difference, right?

When towing my 1500 kg caravan back and forth through Austria the last few weeks, I have been in several occasions where I was towing the van up a motorway incline with a (according to the dashboard) empty battery. Lets say 4 - 5% @ 95 kph. The only thing I ever noticed is that the engine switches from parallel to serial mode when finally reaching 22 % SOC (and back into parallel mode when reaching 25% again). I have not noticed any reduced performance at any time.

I must say I have not tried to see what would happen if I would floor it at 22% SOC or below, because I wanted to prevent appearance of the turtle. But I wonder, even when not driving a PHEV as a milk float, how hard do you have to push it to get down to 22% solo? Even when there are some hills around?

@Maby, by the time you experience the reduced performance you talk about, have you seen the turtle?

 

[maby]

No, I've never seen the turtle - I take care to never let it get that low. But I have experienced high engine revs when accelerating hard or climbing a long hill - generally when the battery meter is reading completely empty - as in no bars showing.

Having experimented quite a lot, I've come to the conclusion that a lot of the problem with the over-revving engine is that the car gets into a state where it has difficulty switching from serial to parallel hybrid mode. With the battery close to empty, you accelerate hard and the engine revs have to go up high in order to compensate for the lack of power out of the battery. You get up to the speed where it could be switching to parallel mode, but the engine revs are too high to allow the clutch to engage and you can end up in a mode where you are running at 50mph in serial mode with a flat battery, screaming engine and unable to accelerate further. The car is unwilling to override the throttle position which would result in a momentary deceleration, so you can get stuck in this state. I have a long uphill out of our town and have experimentally forced this condition - if I ease off the throttle a bit, the revs drop, the car momentarily slows, then the clutch engages and I'm in parallel mode with power to carry on accelerating.

 

[jaapv]

If you lose the last bar you are under 27% and into reserve power. That means the car will still perform normally and it will attempt to run the charge up to 27/30% (or maybe 25% as Anko says). That works the same way as pushing the Charge button in other situations. Of course it will rev up the ICE then.
It also means you are demanding more power than it can deliver at that moment, otherwise you would not have pushed it this deep. I would say it is quite normal behaviour.
I do not believe that the engine can have "too high revs" to engage the clutch. The transitions are seamless, which means that the motor management is controlled by the computer that is aware of the transmission speed.
I think that you are seeing a car that is doing an emergency charge and as soon as you lift your foot off the accelerator the power balance shifts so it can switch to parallel.

My point is that in my experience there is no difference in car response whether one or all bars are showing (except of course regen, it cannot work with a full battery).

 

[maby]

....
I do not believe that the engine can have "too high revs" to engage the clutch. The transitions are seamless, which means that the motor management is controlled by the computer that is aware of the transmission speed.
....

My experiments indicate that you can get it into a state where it cannot engage the clutch. Get the battery close to empty and accelerate quite hard from stationary - up a long hill is easiest. It starts off in serial hybrid with the engine revving high to provide the power to the motors - there is no proper mechanical gearbox, so it can only engage the clutch when the engine revs match the road speed, but they never will - at 30mph, you are running with the engine revs that would go with 60mph. As you get up to the speed where it could transition to parallel mode, the engine is revving hare to produce the power that the motors are demanding and the clutch cannot be engaged - you are stuck in serial hybrid with the engine screaming and the speed creeping up as others have observed. It needs the counter-intuitive lift of the right foot in order to be able to continue to accelerate.

 

[anko]

I think that you are seeing a car that is doing an emergency charge and as soon as you lift your foot off the accelerator the power balance shifts so it can switch to parallel.

I think not.

I believe there are three reasons for the high revs:

1 - The following combination of factors
-- You are driving less than 40 mph
-- The battery is below 27% and / or you run save or charge mode
-- There is a somewhat larger power demand

As you are at a sub-parallel mode speed, the engine can and will provide all the power needed for driving the car, preventing the battery from being drained (further). Revs will go up and down with power demand.

When towing a caravan up a not to steep hill in charge mode, you will see that then engine is capable of charging the battery a little bit, until you hit 40 mph. Than parallel mode is engaged and the power output of the engine is strongly reduced. As a result, the battery starts being drained.

2 - The power demand is more than can be delivered by the battery (60 kW after losses) + what can be delivered by the engine in parallel mode. Serial mode will be engaged and you will see is that the battery output is strongly reduced as soon as the high revving starts. This is possible because the output of the engine is suddenly much higher.

Towing up hill at for example 55 MPH may show 100% engine load at approx. 2700 RPM + 20 kW from the battery. When you then hit the accelerator, this could easily change to for example 90% engine load at 4100 RPM + 10 kW into the battery. When slowly lifting the accelerator, the car will revert back to 100% @ 2700 RPM + 20 kW.

3 - What Jaap nicely calls "emergency charge" (let's keep that expression ). The emergency charge starts at 22% and does not stop until SOC is increased back to 25% (which is another threshold than the 27 or 30% threshold for automatically starting the engine at slow or high speed). Not even when you totally lift the accelerator. Only when it reaches 25% it will go back to parallel mode (as long as conditions for 1 and 2 are not met).

In this last mode, fluctuations in throttle position directly translate in fluctuations in battery (dis)charge. You can easily prevent going below 22% or you can even hover around 22%, as long as you are willing to play with the throttle as necessary. But you cannot stop the revving, other than by letting it get back to 25%. This is why I don't think Maby has encountered emergency charging in the situation he described.

For modes 1 and 2, I am rather convinced that battery output is not reduced. For mode 3, it is my personal experience that battery output is not reduced as long as you stay near 22% or above. This is confirmed by Mitsu documentation. It says:

At 22% A/C and heater are switched off
At 20% Power is reduced and a turtle is shown in the display
At 13% All comes to an end, if no fuel is available

 

[anko]

As you get up to the speed where it could transition to parallel mode, the engine is revving hare to produce the power that the motors are demanding and the clutch cannot be engaged - you are stuck in serial hybrid with the engine screaming and the speed creeping up as others have observed. It needs the counter-intuitive lift of the right foot in order to be able to continue to accelerate.

That cannot be right :ugeek:

In serial mode at 40 MPH (potential cutover speed), the engine can provide 60 kW of power to the wheels, via the E-motors (after conversion losses). This will require almost 100% engine load at 4100 RPM. But in parallel mode, engine speed will be reduced to approx. 1700 RPM and engine output to the front wheels will be reduced to approx. 30 kW at best. Even at 100% engine load. So, effectively power delivered by the engine to the wheels would be cut in half when the clutch would be closed. And this is why the clutch cannot be closed: it is not the revs that are to high. It is the power demand that is to high.

By no means can your car perform better in parallel mode than it can in serial mode at speeds below 75 MPH. Only at approx. 75 MPH and above will the engine in parallel mode (approx. 60 kW @ 3150 RPM, but no conversion losses) start to outperform the engine in serial mode (70 kW @ 4100 RPM, but with conversion losses) in terms of power delivered to the wheels.

You must have noticed that, when flooring it while cruising at speeds between 40 and 75 MPH, the engine will switch from parallel to serial mode. This is because it increases performance of the car at these speeds.

I am sure this line of thinking also explains why the engine will never run in serial mode above 75 MPH. Serial mode will only add conversion losses once you get to that speed.

 

[Grigou]

I agree with your explanation anko, and agree with you maby for your description of the phenomenon.
Like you, in the Alps when the revs are too high I slightly lift my right foot to let the system to switch in parallel mode. And after that, I can accelerate again (not too hard) and stay in this mode.

Like you maby, I think (in long uphill driving of course) that the engine's revs are higher when the soc is low, even with one bar on the gauge. I think that the system takes the soc into account to balance the power between battery and engine.

Since I go often in the Alps (second home), I think that one day I will write "I'am sure" instead of "I think"

 

[anko]

I agree with your explanation anko, and agree with you maby for your description of the phenomenon.
Like you, in the Alps when the revs are too high I slightly lift my right foot to let the system to switch in parallel mode. And after that, I can accelerate again (not too hard) and stay in this mode.

To this, I would agree. But Maby said, he had to lift his foot in order to engage parallel mode, before he would be able to accelerate again. As if acceleration in parallel mode would be better than in serial mode. And that is something completely different.

And may I suggest, this phenomenon is independent of SOC?

Like you maby, I think (in long uphill driving of course) that the engine's revs are higher when the soc is low, even with one bar on the gauge. I think that the system takes the soc into account to balance the power between battery and engine.

Since I go often in the Alps (second home), I think that one day I will write "I'am sure" instead of "I think"

I think I can easily explain why you are correct in your observation. The charge current the battery is willing to accept depends on SOC. The lower the SOC , the higher the max charge current. In order to provide this higher current, the engine needs more revs. Hence, more revs at lower SOC (in serial mode only, of course). The difference in max charge current between a near full and a near empty battery can easily be 15 or more kW, I believe.

I have mentinoned this several times, as I believe this makes the car more efficient: the higher the charge current, the more often the engine can be turned off. This is why I think using Save or Charge mode to much is a bad thing from an efficiency perspective.

But Maby claims low SOC makes the car mor sluggish. And that (although higher revs might make it feel that way) would again be a different thing.

BTW: I don't think there is any balancing going on. The engine provides power needed for driving and any reserves are used for charging, within the limit of what the battery is willing to accept. Until you meet the turtle, of course. Then, it is a different ball game

 

[Grigou]

For your first question anko, my answer is that you can suggest it, for me there is no difference.

For the further part of your post I could agree with your explanation, especially if you say that the difference of charge currents between an "empty" (1 bar or 0 bar) battery and an almost full battery can reach more than 15 kW.

So OK, probably there is not intentional balancing in the system, but the curve of charge power between an empty and full battery provides a factual balancing

 

[anko]

..., but the curve of charge power between an empty and full battery provides a factual balancing

A bit off-topic, I guess, but does it? If so, what is being balanced and over what?

Keep in mind, when the charge current increases, this does not mean that less power goes to the wheels. Instead, the total output of the engine increases. Or the other way around. A smaller charge current does not automatically result in driving faster. The output of the engine will be reduced instead. There is no trade off between power for driving and power for charging. There is power for driving plus more or less power for charging.

Again, until you hit the 22% mark.

If any balancing is going on, it is when the charge current is being reduced when more power is needed for driving, once the engine load has reached 100%. Or can be increased when less power is needed for driving. But, IMHO not as a result of changes in battery SOC.

If the latter was the case, a higher SOC would result in more engine power being available for driving and the Maby would be right again. And we cannot have that ...