Best speed to charge battery during long journeys?

[Steepndeep]

Hi

During long journeys, say more than 200 km, what is the best tactics for low fuel consumption? And let´s assume we apply obvious tactics as starting with full SOC and arriving with battery empty and also applying sensible speed and driving sensibly. If the journey is a combination of highway driving with no congestion and some city passthrough at low speed and stop and go traffic. Shall I just let the Outlander do its thing or shall I force charge at highway traffic and then run through the cities at pure EV? And if the latter what is the optimum speed to charge the battery?

 

[jaapv]

Stop in a parking spot and run charge. The least miles for the most charge :twisted:

 

[Grigou]

Hi

During long journeys, say more than 200 km, what is the best tactics for low fuel consumption? And let´s assume we apply obvious tactics as starting with full SOC and arriving with battery empty and also applying sensible speed and driving sensibly. If the journey is a combination of highway driving with no congestion and some city passthrough at low speed and stop and go traffic. Shall I just let the Outlander do its thing or shall I force charge at highway traffic and then run through the cities at pure EV? And if the latter what is the optimum speed to charge the battery?

Pure EV for low speed and stop and go traffic is always the best tactic.

At these low speeds you can drive, lets say, 40 to 55 km in pure EV : if it's enough, stay in Save during the rest of the journey (= higher speeds). If you must drive more than these 40 to 55 km at low speed, do not hesitate to pusch Charge for a while at higher speeds.
IMHO there is not a real "optimum" speed to charge the battery, if you are in parallel mode (> 70 kph).

 

[ChrisMiller]

I'm confused (not for the first time). The charge/discharge efficiency of Li-ion batteries is generally cited as 80-90%. So let's imagine I'm cruising down the highway with an empty battery and I know I have a section of urban driving ahead that will need 1 kWhr of electrical energy to get through it. I can either do nothing and let the engine cut in as required to supply the 1 kWhr only when it's needed, or I can press the Charge button and generate 1.1-1.2 kWhr of electricity so that I can get through town on EV only. The only way it can be more efficient to choose the second option (ignoring the fact that it may be 'kinder' to operate on zero emissions in town) is if there's some 'free' surplus power being produced by the engine that I can take advantage of to charge the battery. Does anyone know if this is the case? Or have I got it all wrong

 

[anko]

It is a trade-off between having the engine run longer at high speeds vs having the engine run longer at low speeds. The first can be done in parallel drive, eliminating the need for converting mechanical power needed directly for propulsion to electricity and back by means of generator and e-motors. The second eliminates the need to temporarily store electricity in the battery.

 

[ChrisMiller]

Thinking further about it, I imagine if there were any 'free' surplus energy available from the ICE, Mitsubishi would do their best to ensure they made use of it to increase the battery charge - it's fundamentally what the car is all about. So the only other advantage of generating charge from petrol in advance rather than 'on demand' is if there's a significant overhead involved in starting up the engine. I doubt this could be as high as the 10-20% efficiency loss resulting from storing the charge in the battery.

 

[Grigou]

I'm confused (not for the first time). The charge/discharge efficiency of Li-ion batteries is generally cited as 80-90%. So let's imagine I'm cruising down the highway with an empty battery and I know I have a section of urban driving ahead that will need 1 kWhr of electrical energy to get through it. I can either do nothing and let the engine cut in as required to supply the 1 kWhr only when it's needed, or I can press the Charge button and generate 1.1-1.2 kWhr of electricity so that I can get through town on EV only. The only way it can be more efficient to choose the second option (ignoring the fact that it may be 'kinder' to operate on zero emissions in town) is if there's some 'free' surplus power being produced by the engine that I can take advantage of to charge the battery. Does anyone know if this is the case? Or have I got it all wrong

You have to take in account the whole system's efficiency (engine efficiency + electronics + battery efficiency).

Charging and discharging later is not efficient from the electronics + battery's only point of view.
BUT the engine's efficiency in parallel mode when charging is significantly higher than the engine's efficiency in serial mode at low speed.
So globally, it seems to be better to charge at higher speeds and discharge at low speeds. But nobody, AFAIK, has measured the difference with a good scientific method .......

 

[anko]

You have to take in account the whole system's efficiency (engine efficiency + electronics + battery efficiency).

Charging and discharging later is not efficient from the electronics + battery's only point of view.
BUT the engine's efficiency in parallel mode when charging is significantly higher than the engine's efficiency in serial mode at low speed.

The engine's efficiency is not affected by the hybrid mode, parallel or serial . But as you said, you have to look at the whole system .

What is important IMHO is that the efficiency of the engine (kWh produced per liter of fuel) goes up when it is charging while propelling compared to when it is not charging while propelling the car. Apparently, the highest efficiency is achieved when engine load is around 75 - 805% (depending on RPM). And this is indeed why the car adds a charge load to the normal driving mode.

 

[ChrisMiller]

Thanks for all the helpful and thoughtful comments. I've got to go to Oxford twice this weekend (30 miles/50 km each way). So I'll try a bit of an experiment - one run leaving the car alone to do its own thing and the other using Save to keep some charge to tackle the Chiltern hills on my way home. I'll let you know if I see much/any difference.

 

[Grigou]

You have to take in account the whole system's efficiency (engine efficiency + electronics + battery efficiency).

Charging and discharging later is not efficient from the electronics + battery's only point of view.
BUT the engine's efficiency in parallel mode when charging is significantly higher than the engine's efficiency in serial mode at low speed.

The engine's efficiency is not affected by the hybrid mode, parallel or serial . But as you said, you have to look at the whole system .

....

I just wrote "in parallel mode when charging" vs "in serial mode at low speed"

 

[anko]

You have to take in account the whole system's efficiency (engine efficiency + electronics + battery efficiency).

Charging and discharging later is not efficient from the electronics + battery's only point of view.
BUT the engine's efficiency in parallel mode when charging is significantly higher than the engine's efficiency in serial mode at low speed.

The engine's efficiency is not affected by the hybrid mode, parallel or serial . But as you said, you have to look at the whole system .

....

I just wrote "in parallel mode when charging" vs "in serial mode at low speed"

I know.

 

[Bladevane]

I'm gradually forming the opinion that when driving normally in traffic the biggest effect on efficiency is by using B0 as much as possible. The inertia contained in the PHEV is massive and if you can cruise to a halt rather than brake (regeneratively or mechanically) it must be better from an efficiency perspective - of course whilst still driving with due consideration for other road users, specifically those behind you.

 

[greendwarf]

Thinking further about it, I imagine if there were any 'free' surplus energy available from the ICE, Mitsubishi would do their best to ensure they made use of it to increase the battery charge - it's fundamentally what the car is all about. So the only other advantage of generating charge from petrol in advance rather than 'on demand' is if there's a significant overhead involved in starting up the engine. I doubt this could be as high as the 10-20% efficiency loss resulting from storing the charge in the battery.

The car does generate surplus energy (albeit not "free") in normal use when using the ICE, which is why there are periods when the engine cuts out and runs on battery even in Save. Whilst there are fine distinctions to be made, no doubt, about the most efficient performance strategy, the answer also depends on your view on urban traffic fumes and whether you want to sit in slow moving traffic breathing in those you have generated or help us all by travelling in EV in built up areas :mrgreen:

BTW - unusually unhelpful response from jaapv to, presumably, a newbie

 

[ChrisMiller]

the biggest effect on efficiency is by using B0 as much as possible

Not if that involves speeding up, coasting for a while and then speeding up again - basic physics tells us that must be suboptimal. If you know you're going to have to slow down or stop at some point up ahead, and can time it to perfection, B0 may be an efficient way to do so - but I suspect (in my neck of the woods, anyway) such opportunities will be extremely rare.

 

[jaapv]

Thinking further about it, I imagine if there were any 'free' surplus energy available from the ICE, Mitsubishi would do their best to ensure they made use of it to increase the battery charge - it's fundamentally what the car is all about. So the only other advantage of generating charge from petrol in advance rather than 'on demand' is if there's a significant overhead involved in starting up the engine. I doubt this could be as high as the 10-20% efficiency loss resulting from storing the charge in the battery.

The car does generate surplus energy (albeit not "free") in normal use when using the ICE, which is why there are periods when the engine cuts out and runs on battery even in Save. Whilst there are fine distinctions to be made, no doubt, about the most efficient performance strategy, the answer also depends on your view on urban traffic fumes and whether you want to sit in slow moving traffic breathing in those you have generated or help us all by travelling in EV in built up areas :mrgreen:

BTW - unusually unhelpful response from jaapv to, presumably, a newbie

I'll keep my tongue straight in future...

 

[ChrisMiller]

FWIW (very little, I suspect) the results from my trips to Oxford were:

(a) no manual 'interference' - out: 155 mpg; back: 34.2 mpg; average : 56.0 mpg

(b) 'Save' once the motorway has been reached - out: 65.2 mpg; back: 49.2 mpg; average: 56.1 mpg

It's about 30 miles (50 km) each way, so the battery was exhausted by the time Oxford was reached on the first trip; use of 'Save' left about 7 miles in the battery. But on overall fuel consumption, there would appear to be very little in it.

 

[gwatpe]

I have also found little difference with returned economy for different operation modes. The benefit I find is the reduced series hybrid operation as a result of saving some battery. The lower cabin noise levels make up for having to press the SAVE button 100 fold.

 

[ChrisMiller]

The benefit I find is the reduced series hybrid operation as a result of saving some battery.

I would have thought that achieving similar fuel consumption equates to similar amounts of time with the ICE operating. What am I missing?

 

[gwatpe]

The benefit I find is the reduced series hybrid operation as a result of saving some battery.

I would have thought that achieving similar fuel consumption equates to similar amounts of time with the ICE operating. What am I missing?

I have a particular section of road with a transition from 80kph down a hill section to a 100kph section with an uphill grade, that I usually have SAVE mode engaged. My PHEV behaves the same as my mates, and drops out of parallel hybrid to series hybrid in the same way when the power is applied to accelerate in the 100kph section. ICE transitions from pleasant to drive, to ICE screaming.

My observations over almost 2 years ownership is biased with many tens of thousands of km with ICE operations. Soft pedaling at speeds under 70kph gives a quiet drive, when the PHEV operates series hybrid and parallel hybrid operation above 80kph has a similar quiet drive effect. I have found that consuming the electricity at high speed to deplete the battery, in NORMAL mode, leaves the computer less options for parallel mode operation at higher speeds [above 80kph], and the series hybrid kicks in for additional power needs, and this results in a less pleasant drive overall. There is not enough in it for economy savings for me to run with the depleted battery compared to keeping some additional reserve in it.

WRT best speed for recharging, 90-100kph, for the times I have needed to do it. Never tried to recharge at lower speeds, in series hybrid, as long journeys would typically be at higher speeds anyway.

 

[Steepndeep]

Thanks for all the replies

Looks like playing around with Save Mode gives little or no real fuel savings, so then there are the other benefits to look at.

1 For longer journeys when you have highspeed and some slow speed driving I will play with Save just to avoid running ICE when in cities.

2 Living in Sweden where it is actually very cold in winter (some times) you should never run the ICE for a short time after a cold start. If the ICE starts it should run at least 15 minutes or longer depending on temperature.