Hello and question about using ICE for efficient charging

[PaulRB]

Hello everyone, I have been driving my GX4h for just over a week now, lots to learn still, really enjoying it.

My daily commute is around 25 miles each way. Just over half of this is motorway, and much of that is slow and crowded with roadworks and 50mph limits. The remainder is twisting, hilly, country roads, finishing around 1,000 ft above sea level. I am fortunate to be able to recharge both at home and at the office.

In one direction, I can complete the journey on electric power with 1/4 charge to spare. In the other direction, I can't quite manage the full distance. The ICE comes on in the last couple of miles. This is the journey with much more uphill climbing, as you would imagine.

So my questions are:

Any tips for achieving the difficult journey without using petrol? Obviously I am aware, but probably still have much to learn, about regenerative braking, use of the paddles (I mostly drive on "B5" setting), driving cautiously and smoothly as possible etc.

If I need to burn a little petrol to complete the journey, which is the most efficient part of my journey to do this (motorway, country roads...)? Does it make little or no difference in practice?

Apologies if this is a well-worn subject.

Thanks,

Paul

 

[maddogsetc]

Hi Paul and welcome

I suspect you'll get lots of differing opinions on this one :lol:

Obvious things are minimal use of all accessories, especially AC (and heating when we get to winter) and use Eco mode at all times.

With lots of hills you might want to try the B0 (if you can find it?) coasting option vs. using B5 to maximize regeneration. One or two threads on here with a bit about that. Another popular idea (and one that most of us seem to agree on) is to use Save on the fast-moving motorway sections but only if you know that you won't be able to do the whole trip on EV mode.

My suggestion would be to try various different strategies, resetting the Manual data file on Trip/Eco Info at the start of each difficult leg. Make sure you record the results that you get at the end of each leg though because MMCS cannot be relied upon not to reset itself spuriously. Over 2 or 3 weeks you should be able to identify the pattern and see which strategy works best, if there is one. Truthfully I doubt you will be able to influence it that much and it might be best just to let the car do it's own thing.

 

[thegurio]

I suspect you'll get lots of differing opinions on this one :lol:

Ain't that the truth...

Obvious things are minimal use of all accessories, especially AC (and heating when we get to winter) and use Eco mode at all times.

One thing I have learnt within less than 24 hours of owning it, is that your inf on the hearing cost you 10k's (6.5miles) of range. However the seats barely impact at all. This I replicated a few times throughout the day...

With lots of hills you might want to try the B0 (if you can find it?) coasting option vs. using B5 to maximize regeneration.

I've found a combination of both worked today, got another 2 k's out of it today.

My suggestion would be to try various different strategies, resetting the Manual data file on Trip/Eco Info at the start of each difficult leg. Make sure you record the results that you get at the end of each leg though because MMCS cannot be relied upon not to reset itself spuriously. Over 2 or 3 weeks you should be able to identify the pattern and see which strategy works best, if there is one. Truthfully I doubt you will be able to influence it that much and it might be best just to let the car do it's own thing.

I've found today I was mucking around with things so much that I went from using 1.9l, to using 7.6 (my final result after charging and idling etc.) that if I left it alone it may well have been 4l (what I'm aiming for) so I've no idea...

 

[user 258]

Hi
Apart from not using a/c or heating and gentle driving, if you still can't complete that leg in EV mode the just run in save mode for a couple of k's on the motorway when your speed is at the highest you are likely to achieve and if you still have too much EV range gradually reduce the duration you use sabre mode. With a little practice you could have perfection.
Kind regards
Mark

 

[maddogsetc]

sabre mode

What model are you driving Mark! :lol:

Agree with all of the above though.

 

[thegurio]

sabre mode

What model are you driving Mark! :lol:

Agree with all of the above though.

Bahahaha.... I was thinking that - I didn't see that on mine as an option lol

 

[PaulRB]

Thanks for the replies everyone.

Eco mode at all times.

What does Eco mode actually do that you couldn't do yourself by driving more carefully and running the a/c or heating at minimum?

With lots of hills you might want to try the B0

I have tried it. I can see it would work great on roads that were hilly but straight. You could coast down one hill, building up speed to get you up the next hill easier. But my roads are winding and narrow with high hedgerows, many sharp bends and tractors lurking around blind corners. Even the bends you could take at higher speeds, its not safe to do so in case of traffic in the other direction.

use Save on the fast-moving motorway sections

This was my assumption too, and I have tried it and completed the rest of the journey on electric. However... are we making the assumption that this is the best time to do it, based on our old knowledge that conventional ICE cars are at their most efficient on the motorway? It this also true for the PHEV? When the ICE starts up automatically to recharge the batteries, it does not sound like it runs at high revs like it would on the motorway. Maybe it generates charge more efficiently at lower revs...

Another question then: Save or Charge when on the motorway? The aim is to exit the motorway with a certain level of charge in the batteries, but is it better to hit save as soon as the charge drops to that level, or allow it to drop further, then use Charge to bring it up again over a shorter period? Or is there effectively no difference?

My suggestion would be to try various different strategies, resetting the Manual data file on Trip/Eco Info at the start of each difficult leg. Make sure you record the results that you get at the end of each leg though because MMCS cannot be relied upon not to reset itself spuriously. Over 2 or 3 weeks you should be able to identify the pattern and see which strategy works best, if there is one. Truthfully I doubt you will be able to influence it that much and it might be best just to let the car do it's own thing.

I shall enjoy doing that, I am a geek. Must read the manual chapter on the Trip/Eco screens, I remember the sales guy demonstrating them. Is it possible to dump this data onto the SD card, in some format I could load into Excel? Or access it over Wifi?

I have also yet to get my smartphone paired up on bluetooth and connected on Wifi, and the PHEV app loaded.

Currently at almost 500 miles, around 1/8 - 1/4 tank used.

 

[PaulRB]

your inf on the hearing cost you 10k's (6.5miles) of range.

I assume you meant to type "heating" but what did you mean by "inf"? information?

I've found today I was mucking around with things so much that I went from using 1.9l, to using 7.6 (my final result after charging and idling etc.) that if I left it alone it may well have been 4l (what I'm aiming for) so I've no idea...

Lost me there. Are you talking litres of fuel? Over what distance?

Apologies on behalf of all us Brits. Still in the steam age with our miles and gallons! As bad as the Americans. (Different, but as bad. Think a mile is the same but a gallon isn't.)

 

[maddogsetc]

However... are we making the assumption that this is the best time to do it, based on our old knowledge that conventional ICE cars are at their most efficient on the motorway?

My belief is that the ICE will be at it's most efficient when operating in Parallel mode ie. when actually driving the wheels, not topping up the battery. In Series mode you have the losses associated with converting the energy an extra 2 times (kinetic to electrical and back again) and the power curve of ICE's (particularly petrol) means that proportionately more power is generated at higher revs.

So my aim, when I know I'm gonna have to burn petrol, is to use Save at the times when I'm doing at least 60mph. Theoretically only Parallel mode is possible over 70mph and I did have a feeling that it might be better to drive at 70mph to 'force' Parallel mode than at 60mph and let the car decide. However I tried this (in Save) yesterday and I found that even over 70mph it was still selecting Series mode when the load was not great ie. downhill, flat or very slight uphill inclines. As soon as the load increases though, it quickly switches into Parallel mode.

Regarding Charge - I cannot see any case in normal driving where this would be more cost efficient than just letting the car run with the battery depleted. The only reasons I can see for using it is when you know that the demands on the battery are going to deplete it very fast, potentially faster than it can be recharged from ICE, eg. driving in mountains.

I agree with your comments about Eco mode but on balance feel it's worth using. If nothing else it makes the car feel surprisingly sprightly when you forget to turn it on. Which is nice :lol:

 

[user 258]

sabre mode

What model are you driving Mark! :lol:

Agree with all of the above though.

Bloody auto correct! Wouldn't it be great to have a sabre mode though

 

[user 258]

So my aim, when I know I'm gonna have to burn petrol, is to use Save at the times when I'm doing at least 60mph. Theoretically only Parallel mode is possible over 70mph and I did have a feeling that it might be better to drive at 70mph to 'force' Parallel mode than at 60mph and let the car decide. However I tried this (in Save) yesterday and I found that even over 70mph it was still selecting Series mode when the load was not great ie. downhill, flat or very slight uphill inclines. As soon as the load increases though, it quickly switches into Parallel mode.
:

Hi
I agree with pretty much everything you say apart from the above as it is not the theory or what I experience with my PHEV.
The theory is that below 40mph ONLY series hybrid mode is available. Above 74mph ONLY parallel hybrid mode is available. Between 40 & 74mph either mode is available with parallel hybrid mode being the preferred option as it is more efficient, providing it can give the amount of power required from the engine since engine speed is dictated by road speed. Speeds are of course genuine speed not speedo speeds so 74mph may well be closer to 80mph indicated.
In practice, with my gentle driving style at least, when I accelerate and get to about 42mph it switches to parallel hybrid mode and pretty much stays there.
When you see it in series hybrid mode with a low load, could it be that it has actually turned the engine off or is the engine definitely still running?
kind regards
Mark

 

[maddogsetc]

In practice, with my gentle driving style at least, when I accelerate and get to about 42mph it switches to parallel hybrid mode and pretty much stays there.

Is that with Save on? Without Save most of my motoring is 100% EV up to say 60-65mph. With Save on it's a different matter of course as the system will be topping up the battery from time to time whatever the speed / load conditions.

When you see it in series hybrid mode with a low load, could it be that it has actually turned the engine off or is the engine definitely still running?

With Save on, I'm seeing it switch frequently between all 5 modes (pure EV, Series, Parallel, Parallel + charge; & Regen). So on a gentle downhill it might coast (hmm, for all 5 modes read all 6 modes. What have the Romans ever done for us...) or if I ask for slight acceleration it might be pure EV. As the road flattens out (or perhaps as the charge drops sufficiently for it to detect it needs a top up?) it'll switch to series. As we start to climb gently it'll switch to parallel but keep charging perhaps or maybe just run in parallel. This is all around 50-70 mph.

I thought the cut-off for Parallel only was 70mph - if it's 74mph that might explain why I've not been able to 'force' parallel mode.

On a related but different note, I was pondering yesterday whether running at higher speeds with a little a/c might actually be more efficient than running with the windows / sunroof open due to the increase in wind resistance? Certainly wouldn't apply at lower speeds but on the dual carriageway the difference might not be that great. There's another one to test

 

[maddogsetc]

74mph may well be closer to 80mph indicated

Missed that bit on my first read - it's a very good point.

 

[user 258]

In practice, with my gentle driving style at least, when I accelerate and get to about 42mph it switches to parallel hybrid mode and pretty much stays there.

Is that with Save on? Without Save most of my motoring is 100% EV up to say 60-65mph. With Save on it's a different matter of course as the system will be topping up the battery from time to time whatever the speed / load conditions

Yes, with save on. I think most of your problems, as you say, is that you don't use your engine much

On a related but different note, I was pondering yesterday whether running at higher speeds with a little a/c might actually be more efficient than running with the windows / sunroof open due to the increase in wind resistance? Certainly wouldn't apply at lower speeds but on the dual carriageway the difference might not be that great. There's another one to test

Yes. I've always used a rough rule of thumb that below 40mpg have the windows/sunroof open, above 50mph use the aircon as the open windows costs more in drag than the a/c uses. Between 40-50 do what you want

 

[user 258]

I forgot to add, that unless very warm outside I tend to have climate control ON, with A/C turned off. This gives decent airflow through the car without the noise of the windows being down and without the power consumption of the compressor.

kind regards,
Mark

 

[PaulRB]

My belief is that the ICE will be at it's most efficient when operating in Parallel mode ie. when actually driving the wheels, not topping up the battery. In Series mode you have the losses associated with converting the energy an extra 2 times (kinetic to electrical and back again)

I think you nailed it there maddog. That's the crucial rule to keep in mind. If you know you won't make it all the way in electric, Save is better than Charge and use the ICE to drive the wheels directly when you can. Every time we use this amazing machine to convert energy from one form to another (chemical, electrical, mechanical, potential) we inevitably loose a significant % of it as friction/heat. The Laws of Thermodynamics. You can't escape 'em!

and the power curve of ICE's (particularly petrol) means that proportionately more power is generated at higher revs.

That bit, not so sure. Just because an ICE generates more power at higher revs, doesn't neccessarily mean its doing it more efficiently.

 

[DavidEJM]

and the power curve of ICE's (particularly petrol) means that proportionately more power is generated at higher revs.

That bit, not so sure. Just because an ICE generates more power at higher revs, doesn't neccessarily mean its doing it more efficiently.

That's true, bhp is just a factor of torque and revs (power bhp = (rpm x torque) / 5252 apparently) so it would be better to look at the torque curve to see where the engine is running at its most efficient.

 

[PaulRB]

I am finding, as someone else mentioned earlier, that even above 50mph, if I switch to Save mode, I sometimes see the display indicating that the engine is charging the battery and the battery is powering the motors, ie. Series hybrid mode, when I would expect to see the engine powering the wheels directly and maybe also charging the battery, ie. Parralel hybrid. Using series mode when parralel could be used must be less efficient. The energy is getting transformed twice, with the inevitable associated losses.

Is there a trick to avoid this that anyone has discovered?

 

[user 258]

I am finding, as someone else mentioned earlier, that even above 50mph, if I switch to Save mode, I sometimes see the display indicating that the engine is charging the battery and the battery is powering the motors, ie. Series hybrid mode, when I would expect to see the engine powering the wheels directly and maybe also charging the battery, ie. Parralel hybrid. Using series mode when parralel could be used must be less efficient. The energy is getting transformed twice, with the inevitable associated losses.

Is there a trick to avoid this that anyone has discovered?

When the engine first starts, when you select save mode, the engine will run in series hybrid mode while the engine and catalytic converter warm up (to reduce wear and emmissions). Engine rpm being about 1500 during warmup.

Personally, I find that even under acceleration (but not rapid) as soon as the road speed gets to about 42mph the engine revs drop and parrallel hybrid mode is selected. It almost always then remains in this mode unless the car decides to run in pure EV mode to discharge some of the charge that has built up in the battery. If you floor it then it will move to series hybrid mode so it can rev the engine high to give you the power you need.

Could you be seeing series hybrid mode above 50mph only during warm up?

Kind regards,
Mark

 

[user 422]

So far I have done just over 1500 miles in 3 weeks - one journey every week 90% motorway of 240miles ( round trip ) with an overnight charge in the middle - all the rest are journeys of 25-30 miles round country roads...

Its my conclusion that I can't out guess the Vehicles Control system to get better MPG - Speed and excessive Acceleration equate to lowering the overall MPG...
I have tried almost every combination of Save & Charge and Eco during both the short and long trips and the best mileage figures come from leaving the Mode in NORMAL and being light on the pedals ( both Throttle and brake ).
The long motorway trips - let it use EV at the start and use it ALL ( unless you are heavy or know that you will be doing LONG steep hills somewhere - then drop into Save mode at approx 40% used battery) , best cruise speed is 64 MPH - pick overtakes well in advance to minimise braking or excessive acceleration, Cruise control up slopes, but if possible drop to coast for long down slopes to build up momentum ( if traffic does not allow this use B0-B5 to recover energy to battery on downslopes - I can get 56-58mpg over 120miles this way... If you want to drive around your destination town in EV go to charge mode for the last 15-20 min of motorway - but aim for only just enough charge to complete the town mileage.

round town - its normal EV and charge when ever needed from charge point. (if its free)

When in Charge or Save mode the system will decide from around 40 MPH whether to engage Serial or Parallel ICE mode...

The Paddles - B0 equals a normal car coasting with the clutch disengaged, B5 = enough regen brake to recover 95% of the energy used over 1 mile of steep climb - for example climb Ditchling Beacon to the car park would take the EV range from 22 to 17 - descend using ONLY regen braking to control speed around 30mph and the EV range goes back to 21.

The B1 to B5 settings just transfers what the Brake pedal does over the beginning of its travel to the OFF position of the throttle pedal - i.e. in B0 pressing the brake lightly increases the REGEN action and you can feel when you reach the actually Brake application as the pedal movement goes hard.

Just my 2pw