Another 'save' question

[vs2]

In NZ where I live we have a lot of hills.

Tomorrow I'm going on my 1st out of town 400km trip.

If I'm driving in 'save' mode with battery at say 50% and I have just gone up a long steep hill and I start down the other side using b3-b5 and some brake pedal as well will the battery charge past my save setting to say 60%?, and if it does will that be my new save level or do I have to turn off save and set it again.

 

[JSC]

You'll need to switch save off, use the paddles to gain charge while you're going down hill and then re-select Save. If you leave it on, it will utilise any additional charge you build up and keep you at 50% SOC

 

[vs2]

Thanks. So as a rule of thumb push save at 50%, leave it there and try and use any battery you have left before you get to your next charge station.

 

[ChrisMiller]

If your objective in using Save is to reduce your fuel consumption, my experimentation suggests it makes no detectable difference. If you leave the car to do its own thing, it lets the battery state drop to about 15% and will then use the engine as necessary to oscillate about that value. Pressing Save simply instructs the car to do the same thing, but around whatever value of charge you set. So if you end your run on 'empty' having used Save on the way, you'll get almost exactly the same fuel usage as if you hadn't used Save at all. But if you have a bit of juice left in the battery, then that will have been 'wasted'.

I think the main value of Save is if you know there's a section of your journey ahead that is going to be severely congested, because of road works or urban conditions, and you want to be able to complete that section on battery power, either to improve fuel consumption or to avoid emissions around other people.

My opinion only - others (I'm sure) will disagree.

 

[vs2]

Good points. Thanks. For me I will probably try and save about 50% and not primarily for 'stop and go' traffic but more for keeping out precious dog heated/cooled whilst we are in a café somewhere.

Edit: And I know some of you do exactly this, as in leave car running with FOB in car and use key to lock.

 

[anko]

You'll need to switch save off, use the paddles to gain charge while you're going down hill and then re-select Save. If you leave it on, it will utilise any additional charge you build up and keep you at 50% SOC

Pretty sure this is not correct. The Save level is known to drift. It can drift down when you are driving uphill and the engine is not able to maintain SOC at the set level. If can also drift up when going down hill and you are regenning more power than what is needed to maintain SOC.

 

[anko]

Thanks. So as a rule of thumb push save at 50%, leave it there and try and use any battery you have left before you get to your next charge station.

If you mean 50% on the gauge, that translates to about 65% real. At that SOC, the max charge current is reduced a bit (to spare the battery) resulting in a slightly reduced overall efficiency. If it is all the same to you, I would keep it just below 50%

 

[anko]

If your objective in using Save is to reduce your fuel consumption, my experimentation suggests it makes no detectable difference. If you leave the car to do its own thing, it lets the battery state drop to about 15% and will then use the engine as necessary to oscillate about that value. Pressing Save simply instructs the car to do the same thing, but around whatever value of charge you set. So if you end your run on 'empty' having used Save on the way, you'll get almost exactly the same fuel usage as if you hadn't used Save at all. But if you have a bit of juice left in the battery, then that will have been 'wasted'.

I think it was Trex who has done the test for us, showing that there were substantial differences in efficiency between running a high SOC versus a low SOC. At least, when you consider a penalty of 5% or more substantial.

..., it lets the battery state drop to about 15% and ...

Lets hope not. At 15% the battery will probably die. Or risk be severely damaged. Depending on your speed, the low water mark is somewhere between 26 and 30.5%. Only when you are asking very much from the car with an already low SOC, it may go down even further. At 20%, output will be reduced and heater and A/C will stop to function. At 17%, your car will come to a halt.

 

[maby]

...

I think it was Trex who has done the test for us, showing that there were substantial differences in efficiency between running a high SOC versus a low SOC. At least, when you consider a penalty of 5% or more substantial.

....

Trex did run a series of tests which seemed to indicate a penalty of up to 8% for running in Save on full charge. But his numbers also indicated that almost all the difference in fuel consumption occurred between 100% charged and 50 or 60% charged - there was very little difference between 50% charge and 0% charge (all figures relative to the charge display, so 0% is still 20% more or less in absolute terms). For a long journey, possibly lasting several days, I generally run on "Normal" for a few miles to bleed off some charge, then switch to "Save" to ensure that I have plenty of reserve for acceleration boost.

That said, I have never been reliably able to detect any difference in fuel consumption related to SOC. Yesterday was a good example - I had to drive about 25 miles each way to Heathrow airport and back, and had forgotten to put the car on charge, so I did it on a totally flat battery. Temperature was about 16 degrees and traffic on the motorway was moderate most of the time. Over the round trip I averaged about 35 mpg - my experience of doing similar trips in Save on full charge would lead me to expect that, or better.

 

[anko]

Trex did run a series of tests which seemed to indicate a penalty of up to 8% for running in Save on full charge. But his numbers also indicated that almost all the difference in fuel consumption occurred between 100% charged and 50 or 60% charged - there was very little difference between 50% charge and 0% charge (all figures relative to the charge display, so 0% is still 20% more or less in absolute terms).

And this is why I wrote:

If you mean 50% on the gauge, that translates to about 65% real. At that SOC, the max charge current is reduced a bit (to spare the battery) resulting in a slightly reduced overall efficiency. If it is all the same to you, I would keep it just below 50%

For a long journey, possibly lasting several days, I generally run on "Normal" for a few miles to bleed off some charge, then switch to "Save" to ensure that I have plenty of reserve for acceleration boost.

I thought we had agreed that running a low SOC does not impact the cars ability to accelerate, but only reduces the amount of time spent in serial hybrid mode and thus reduce the occurrence of 'racing engine'?

 

[vs2]

Interesting stuff. It seems like a little bit here and a little bit there. I run a/c 90% of the time so I am not the best one to get amazing results. I am also not going to focus on pushing buttons on and off to save a few cents, but I will make the most of regenerative braking due to our hilly environment. I brought the car simply because I do 80% of my travels within 20km from home with the odd 400km away so the Outlander PHEV is perfect for me.

I've got a funny feeling after the novelty wears off people just drive in normal mode in 'D' (B2), use the paddles on hills, leave a/c on auto, try not to have the ICE start around town and try to remember to save some battery for stop and go traffic.

 

[HHL]

Interesting stuff. It seems like a little bit here and a little bit there. I run a/c 90% of the time so I am not the best one to get amazing results. I am also not going to focus on pushing buttons on and off to save a few cents, but I will make the most of regenerative braking due to our hilly environment. I brought the car simply because I do 80% of my travels within 20km from home with the odd 400km away so the Outlander PHEV is perfect for me.

I've got a funny feeling after the novelty wears off people just drive in normal mode in 'D' (B2), use the paddles on hills, leave a/c on auto, try not to have the ICE start around town and try to remember to save some battery for stop and go traffic.

That's exactly how I use mine, and you're quite correct, fiddling with buttons is not all that productive. The paddles are great for "engine braking" when required, but that's all. Actually, the car is giving better economy in hybrid mode city driving than my little i30 diesel did!
On longer runs I think it is best to hit save when the battery indicator is at about half, this allows for normal regeneration when braking or going downhill, and also gives it a bit of extra reserve to assist in hill climbing.

 

[anko]

Again, if you care about maximising efficiency (and if possible) try to stay away from 50% (65% real) SOC. Using OBD tools you can easily see that the cars behaviour changes at about that 50% SOC:

- Drive 60 - 70 MPH in parallel hybrid mode, using the CC
- Now check the exact instantaneous fuel consumption and / or engine load using e.g. Torque

When SOC is below approx. 50%, you will see both are very, very stable. Then car controls speed by playing with the charge current.
When SOC is above approx. 50% , you will see that they start fluctuating. The car controls speed by playing with the throttle.

Why this change? Above 50% the max charge current is reduced so much that the car can no longer control speed by just manipulating the charge current.

Personally, I think if controlling speed by means of the throttle was more efficient, the car would do that all the time, regardless of SOC. But more important, the engine load will (in average) be lower at higher SOC, which means fuel is burned less efficient. Think sweetspot.

 

[jaapv]

This also explains another behaviour of the car: If you drive long distances on the Motorway on ACC and have the car in Charge, there will be a speed at which the SOC starts falling. However, it will not flatten the battery: at a SOC around 50 % the drop will stabilize and the car will operate on a fluctuating SOC between low and 50%.

 

[anko]

Why would a reduced charge current cause the SOC to go down? As long as the allowed charge current is not negative, there is no reason for the SOC to go down .... Other then you asking more power than the engine can provide. But this does not depend on SOC.

 

[jaapv]

No-but it depends on the charge rate the car provides.

 

[anko]

There are two separate things:

- How much current can the engine provide?
- How much current is the battery willing to accept?

The first is related to speed and could cause the SOC to go down. The second is related to SOC. I don't see a clear relation between the two.

 

[Grigou]

....

- Drive 60 - 70 MPH in parallel hybrid mode, using the CC
- Now check the exact instantaneous fuel consumption and / or engine load using e.g. Torque

When SOC is below approx. 50%, you will see both are very, very stable. Then car controls speed by playing with the charge current.
When SOC is above approx. 50% , you will see that they start fluctuating. The car controls speed by playing with the throttle.

Why this change? Above 50% the max charge current is reduced so much that the car can no longer control speed by just manipulating the charge current.

....

I wonder if there is a relation between the speed and the SOC threshold which gives a lower efficiency.

Your measurement is at 60 - 70 mph, for a measured SOC threshold at about 50 %. OK.

But is it the same threshold at 120 kph ? The last post of jaapv seems to say "yes" ...

 

[anko]

....

- Drive 60 - 70 MPH in parallel hybrid mode, using the CC
- Now check the exact instantaneous fuel consumption and / or engine load using e.g. Torque

When SOC is below approx. 50%, you will see both are very, very stable. Then car controls speed by playing with the charge current.
When SOC is above approx. 50% , you will see that they start fluctuating. The car controls speed by playing with the throttle.

Why this change? Above 50% the max charge current is reduced so much that the car can no longer control speed by just manipulating the charge current.

....

I wonder if there is a relation between the speed and the SOC threshold which gives a lower efficiency.

Your measurement is at 60 - 70 mph, for a measured SOC threshold at about 50 %. OK.

But is it the same threshold at 120 kph ? The last post of jaapv seems to say "yes" ...

Apart from the fact that 70 MPH and 120 km/h are not that very different ( ), I don't think the threshold is affected by speed. Why would it be? It is the battery health that is a concern. Yet, at higher speeds, the engine load is likely to be closer to the sweetspot to begin with, so a smaller charge current would suffice to get to the sweet spot. And perhaps the reduced charge current at 50% and a bit is sufficient to achieve that. So, the impact of higher SOC on overall efficiency might be a tad lower at higher speeds.

But while discussing the effect of Save mode on efficiency, I do not think it makes a lot of sense to look at the effect of high speeds :mrgreen:

 

[Grigou]

Sorry, I really have read 60-70 kph where you had written mph... and I wrote mph too ! :lol:

Anyway, I see that we have the same reasoning