Battery Save Works Until You Stop...

[maby]

Hi Maby

Surely that means that pressing charge when in parallel mode will not "cost" any fuel as the engine will be directly coupled to the wheels via the CVT and the back EMF from the front motor is being compensated by the drive battery. So there must be an optimum speed/drag/SOC where the charge button works at its optimum charge level?

As has been pointed out by people here that know far more about the working of a petrol engine than I do, there is not a linear relationship between rpm and fuel consumption - if there were, then it would not cost any more to tow a caravan at 50mph in a conventional car than it does to drive the car without the caravan.

 

[Grigou]

"Surely that means that pressing charge when in parallel mode will not "cost" any fuel ..."

What's your pseudo ?
Oh : Neverfuel ? So I understand, now

Pressing Charge implies more load for the ICE, and it costs more fuel of course ... but less than at low speed in serie mode for example.

 

[anko]

I didn't think that the ICE could run the generator when in parallel mode. Otherwise there would be more than 147 kW available at maximum power (87 from ICE for the front wheels, 60 from drive battery for the rears).

Why would there have to be more? The amount of power available to drive the generator is the total amount of power provided by the engine - what is used for mechanically driving the front wheels. Together, these will never be more than 89 kW.

In the technical manual it looks like the ICE is disconnected from the generator when coupled through the CVT? :?

Newsflash: there is no CVT, at least not in my PHEV :idea:

As Maby said, the engine and the generator are always connected to each other, with a fixed gear ratio. When the engine spins, so does the generator. Pretty much like the alternator on a 'normal' car. Similar, the front E-motor and the front axle are always connected to each, with a fixed gear ratio. But the engine + generator assemble can be connected and disconnected from the front E-motor + front axle assemble by means of a (more or less) on / off clutch.

'Funny' enough, when coasting in parallel mode, power is fed from the battery to the generator and from engine to reduce drag from both.

 

[anko]

Hi Maby

Surely that means that pressing charge when in parallel mode will not "cost" any fuel as the engine will be directly coupled to the wheels via the CVT and the back EMF from the front motor is being compensated by the drive battery. So there must be an optimum speed/drag/SOC where the charge button works at its optimum charge level?

Once the car is running in parallel mode, you will always be recharging the battery, unless:
- Insufficient engine power reserve is available, due to strong acceleration, towing or climbing
- The battery is already full
- You have less than 5 liters of fuel in the gas tank (hang on, you cannot be in parallel mode at all when this is the case).
But in above situations, pressing the Charge button would not make a difference either. Hence: pressing the Charge button is of no consequence once you are running in parallel mode. So, although this is probably not what you meant, you were kinda correct: pressing the charge button in parallel mode does not cost any fuel

Since this is the technical Discussions forum, please allow me to point out one potential consequence: when you lift the gas pedal while driving in parallel mode with B0 selected, two things can happen:
- In Charge mode, the engine will keep generating force to charge the battery
- In non-charge mode the engine will sort of idle along. It keeps spinning but does not produce much power. It consumes about 1 or 2 liters of fuel per 100 km. I believe it does so to prevent it from slowing down the car.

As has been pointed out by people here that know far more about the working of a petrol engine than I do, there is not a linear relationship between rpm and fuel consumption - if there were, then it would not cost any more to tow a caravan at 50mph in a conventional car than it does to drive the car without the caravan.

When driving at a steady pace, it takes a certain amount of fuel per mile to maintain that particular speed. Even though the RPMs are fixed for this speed, the amount of fuel needed per mile can vary due to fluctuations in resistance that must be overcome:
- air resistance (drag)
- tire resistance
- resistance of internal moving parts in your car

The generator is a moving part that has a certain resistance. Once you put an electric load on the generator (because you start charging the battery), the resistance of the generator increases. And therfor, the engine must work harder at the same RPMs and more fuel is needed per mile.

 

[gwatpe]

Let me put it this way: if gwatpe could create a device that fires up Charge mode whenever a heavy trailer is detected, I would be more than interested

This would be possible.

My mod does this with drivers help. When trailer or van connected press and hold Charge button. PHEV will remember.this selection when powered down and will remain in Charge mode,even when powered down. And then powered ON again. When trailer no longer connected press and hold charge button to select Normal mode again.

Could be interlocked to a trailer plug. I just needed an option to get around the driver forgetting to press a button in a stop start journey and ending up with a depleted battery, when a battery reserve may have been needed at the end of a journey.

 

[anko]

Let me put it this way: if gwatpe could create a device that fires up Charge mode whenever a heavy trailer is detected, I would be more than interested

This would be possible.

My mod does this with drivers help. When trailer or van connected press and hold Charge button. PHEV will remember.this selection when powered down and will remain in Charge mode,even when powered down. And then powered ON again. When trailer no longer connected press and hold charge button to select Normal mode again.

Nice try. But obviously not what I meant

 

[Grigou]

../..
But in above situations, pressing the Charge button would not make a difference either. Hence: pressing the Charge button is of no consequence once you are running in parallel mode. So, although this is probably not what you meant, you were kinda correct: pressing the charge button in parallel mode does not cost any fuel

The most important words in this demo are "in above situations"

In other situations (ie cruising on roads and motorways) chargin the battery in parallel mode does cost fuel of course, but less than in serie mode under 65 kph
So, ideally the most efficient mode are probably EV at < 65 kph, and Save + Charge at > 65 kph (in solo I mean).

 

[anko]

You wrote:

Pressing Charge implies more load for the ICE, and it costs more fuel of course ... but less than at low speed in serie mode for example.

It looks like nose-picking to differentiate between "charging" and "pressing Charge", but I thought you were looking for the best strategy for driving in parallel mode. And with my response I tried to explain that you have no control over that. Not even by means of the Charge button.

Therefor, I tried to say:

In all but three specific situations you will always be charging when driving in parallel mode, whether you like it or not.
In these three specify situations you will never be charging, not even when you hit charge.

Add these two together and you can see it makes no difference whether you press Charge or not, once you are in parallel mode.

 

[maby]

You wrote:

Pressing Charge implies more load for the ICE, and it costs more fuel of course ... but less than at low speed in serie mode for example.

It looks like nose-picking to differentiate between "charging" and "pressing Charge", but I thought you were looking for the best strategy for driving in parallel mode. And with my response I tried to explain that you have no control over that. Not even by means of the Charge button.

Therefor, I tried to say:

In all but three specific situations you will always be charging when driving in parallel mode, whether you like it or not.
In these three specify situations you will never be charging, not even when you hit charge.

Add these two together and you can see it makes no difference whether you press Charge or not, once you are in parallel mode.

Does the Charge button not influence the rate at which it charges in parallel mode? I know that it will always drift up while in parallel mode, but I believe that it charges faster (and, presumably, burns more petrol) with the Charge button pressed.

 

[anko]

From what I have seen (and I can monitor fuel consumption and charge current in real time) it does not make any difference.

Except for, like it said, the behavior when coasting in B0. With charge active, the engine continues to charge. With charge inactive it idles at the expense of a little fuel consumption.

 

[Grigou]

You wrote:

Pressing Charge implies more load for the ICE, and it costs more fuel of course ... but less than at low speed in serie mode for example.

It looks like nose-picking to differentiate between "charging" and "pressing Charge", but I thought you were looking for the best strategy for driving in parallel mode. And with my response I tried to explain that you have no control over that. Not even by means of the Charge button.

Therefor, I tried to say:

In all but three specific situations you will always be charging when driving in parallel mode, whether you like it or not.
In these three specify situations you will never be charging, not even when you hit charge.

Add these two together and you can see it makes no difference whether you press Charge or not, once you are in parallel mode.

I think (but not sure) that I see where is the confusion : when I said "in parallel mode", I was including the periods when the system switches in EV, in Save mode, even above 65 kph.

 

[anko]

In that case, yes. That explains the confusion

 

[gwatpe]

Let me put it this way: if gwatpe could create a device that fires up Charge mode whenever a heavy trailer is detected, I would be more than interested

This would be possible.

My mod does this with drivers help. When trailer or van connected press and hold Charge button. PHEV will remember.this selection when powered down and will remain in Charge mode,even when powered down. And then powered ON again. When trailer no longer connected press and hold charge button to select Normal mode again.

Nice try. But obviously not what I meant

Would the PHEV make the decision as to how heavy the trailer was :?

Good luck getting MMC to implement a trailer detect system and offer it as a firmware upgrade. :lol:

I traveled to the city yesterday, a 250km round trip, in sticky SAVE mode. Had to stop, and power down many times, as well as multiple stops at traffic lights. Pressed SAVE twice in succession, back to NORMAL and then SAVE again, to stop ICE at lights when needed. This reset the SAVEed setting. Arrived home with 50% battery preserved, from a low of 5 bars at the top of the steep climb on the way home. Got back up to 50% after some steep downhill and the PHEV working back to the SAVEed setting. Prior to installing my mod, the battery would be drawn down close to minimum, while still in the city, and I would need to remember to press CHARGE to bring the battery level back up to a point that the PHEV would maintain parallel hybrid mode on the steep climb on the way home.

From a drivers perspective, it is a no brainer to leave the PHEV in sticky SAVE mode, and press the button to control use of the battery. Much easier than to try and predict what will be needed some way off, or correct a driver error of not pressing a button at the right time, and also reduces unnecessary larger battery increment cycling when driving.

I do get the MMC approach with the NORMAL to flatten the battery first for only urban, short trips. Just would be nice to have an option for times this is not the best mode of operation. I could expect the simple minded power ON programming for a small city hybrid buzz box, but the PHEV is a hybrid sports utility vehicle, and as such should be able to be programmed to remember a mode for the driving needs that are needed at the time. I have just made a mod, that suits my needs, where I control when the battery is used. Remember that my mod gives the driver power ON options, even including the factory, NORMAL option if desired.

BTW my mate with a PHEV that has my mod, who tows a caravan on holiday, praises the mod every time he powers his PHEV ON when he is towing.

 

[jaapv]

Arriving home with a 50% battery does not sound too efficient to me. I always strive to arrive at a charge point that I plan to use with an empty battery.

 

[anko]

I traveled to the city yesterday, a 250km round trip, in sticky SAVE mode. Had to stop, and power down many times, as well as multiple stops at traffic lights. Pressed SAVE twice in succession, back to NORMAL and then SAVE again, to stop ICE at lights when needed. This reset the SAVEed setting. Arrived home with 50% battery preserved, from a low of 5 bars at the top of the steep climb on the way home. Got back up to 50% after some steep downhill and the PHEV working back to the SAVEed setting. Prior to installing my mod, the battery would be drawn down close to minimum, while still in the city, and I would need to remember to press CHARGE to bring the battery level back up to a point that the PHEV would maintain parallel hybrid mode on the steep climb on the way home.

You know what I would be interested in? To hear how exactly your car behaves different when you go out now, allow the battery to drain and start the climb on your way home with a near empty battery. Especially, do you end up in Turtle mode?

I mean, by now we all understand what the mod does, how it works and how clever it is. I mean that. But personally, I am still wondering if there is much added value to having it. I believe there only would be added value, if it would make the difference between ending up near or in the Turtle Zone and not ending up near or in the Turtle Zone (which it could do on long haul tows). I think so, because I still believe that performance is only impacted when SOC drops below 20% and comfort is only impacted (by means of more frequent high-revving) when SOC drops below 22%. If you observe a real difference in performance between SOC >= 20% (as in "as empty as possible, but before you see the turtle Appear) and performance with SOC well above that or if you observe a difference in comfort between SOC >= 22% versus SOC well above that, I would really be interested in technical explanations for such difference.

How long / steep is that hill anyway? Is it a mountain?

, and also reduces unnecessary larger battery increment cycling when driving.

I am not an expert on batteries (far form), but would one larger cycle indeed be worse than many shorter cycles? I am genuinely interested in the answer to that question, as I have no clue. I am equally interested to learn whether cycles alternating around a higher SOC are better or worse than cycles alternating around a lower SOC.

BTW my mate with a PHEV that has my mod, who tows a caravan on holiday, praises the mod every time he powers his PHEV ON when he is towing.

I understand. And so would I. But what is his reaction to the mod when, on the first day of camping, he takes off with his PHEV (without caravan, I mean) to do some groceries and his engine wakes up for an unnecessary cold start, because he forgot to disable sticky Save or Charge?

Personally, I think that would annoy me more than manually starting Save or Charge of few km to (or is it too? ) late.

 

[maby]

Arriving home with a 50% battery does not sound too efficient to me. I always strive to arrive at a charge point that I plan to use with an empty battery.

That certainly makes sense if you are doing relatively short journeys - just beyond your EV range, but read gwatpe's post - he was doing 250km. Even if he could achieve the rather optimistic 50km EV range, that 50% of charge remaining is worth just about 10% of the trip and 10% of the fuel economy - 3 or 4 mpg? Not something that I would lose sleep over. Once you go far beyond the EV range, the battery becomes fairly irrelevant to fuel economy but if you believe that the car handles better with a moderate level of charge, it makes sense to retain it.

 

[jaapv]

Yes, and that is just the point, the car does not handle better with half-charge than it does at 30% AKA empty. You may need a power reserve later on, but that cannot be handled by automation.
He still wasted something like 25 km on the 250, which to me is a significant ca. 10% difference in economy.

 

[Neverfuel]

Yes, and that is just the point, the car does not handle better with half-charge than it does at 30% AKA empty. You may need a power reserve later on, but that cannot be handled by automation.
He still wasted something like 25 km on the 250, which to me is a significant ca. 10% difference in economy.

I have to admit - I don't get it. What is the point of having a PHEV, if you don't use all the available SOC to reduce fuel consumption? I also thought Gwatpe charged from Off grid solar / power storage, so the electricity used to charge up at home is free. It seems like he would be only able to charge 4 - 5 kW if he arrived home with 50% charge left. So - more fuel & less charging, sounds like a lot more expense to me!

 

[anko]

... to me is a significant ca. 10% difference in economy.

To me it is too. And the environment is not impacted by fuel efficiency numbers, it is impacted by burning liters of fuel. Why would you try to save 2 liters of fuel on a short trip and not on a long trip? It is the same 2 liters. I don't get that.

 

[maby]

... to me is a significant ca. 10% difference in economy.

To me it is too. And the environment is not impacted by fuel efficiency numbers, it is impacted by burning liters of fuel. Why would you try to save 2 liters of fuel on a short trip and not on a long trip? It is the same 2 liters. I don't get that.

Really? If I'm spending £20 on something, I will probably go out of my way to save £5. If, on the other hand, I'm spending £2000, then I'm not going to lose any sleep over £5 more or less - life's too short!

Follow up : OK, you are focussing on the environment, I'm focussing on running costs - but the same principle applies as far as I can see - if I'm worried about the environment, I should not have driven the 250km rather than being consumed with guilt about the 25km of EV I didn't use. If I am really worried about the environment, I would not have bought the PHEV at all - a Skoda Fabia would do everything I need and would be at least 50% less damaging to the environment.