Did Mitsu confuse "Save" Mode and "Charge" Mode Above 78 mph (125 km/h)?

[STS134]

I was going down the freeway at a continuous speed of about 85-95 mph (136-153 km/h) yesterday for about an hour, and I noticed some VERY strange behavior from my vehicle.

ABOVE 78 mph/125 km/h, the behavior is as follows:
Normal mode: Vehicle uses clutch to connect engine directly to wheels. Generators and motors do nothing.
Save mode: Vehicle uses clutch to connect engine directly to wheels. Generators generate power and store it in the battery.
Charge mode: Vehicle uses clutch to connect engine directly to wheels. Generators generate power and store it in the battery.

Both Save mode and Charge mode appear to behave identically above 78 mph! In fact, I fired up PHEV Watchdog and looked at the amount of power that was being generated and stored in the battery and it seemed to range from 0 to around 17 kW, depending on instantaneous power demands. And that power did not change when I switched between Save and Charge modes, but it did drop to zero when I entered Normal mode.

BELOW 78 mph/125 km/h, the behavior is different:
Normal mode: Vehicle will use up the battery first, then when the battery hits 1 bar, maintains battery level by either using Series mode or Parallel mode and a hysteresis cycle.
Save mode: Vehicle maintains battery level by using either Series mode or Parallel mode and a hysteresis cycle. The hysteresis cycle appears to be narrower than that used during Normal mode, if the battery level is already depleted.
Charge mode: Vehicle runs the engine and dumps any extra power generated into the battery to charge it.

Anyone else see this happen? It's very strange, but with the current programming, in order to actually MAINTAIN the battery at its present level, I'd have to put the vehicle in Save mode under 78 mph, and then take it out of Save mode and put it in Normal mode whenever I exceed 78 mph, and monitor when I cross that threshold and manually toggle it every single time. If I keep it in Save mode continuously when I am above 78 mph, what happens is that the vehicle keeps charging the battery, and then if I drop under 78 mph for whatever reason (traffic, taking a ramp from one freeway to another, etc.), it will then consume all of the energy that it added to the battery down to the level at which I last placed it in Save mode -- even if it's literally added 6-8 bars, or even charged the battery up to full if I've been doing above 78 mph for long enough.

The whole point of Save mode isn't to charge the battery, or consume battery power, it's to tell the car to keep it at its present level. And when I use Save mode above 78 mph, it fails to do so. I'm wondering if Mitsu actually tested their software at all before pushing it out the door.

 

[littlescrote]

Seems normal to me. There's only so much power available from the ICE, and if you are using a large proportion of it to go so fast, how do you expect to get much charge out of it?

 

[STS134]

Seems normal to me. There's only so much power available from the ICE, and if you are using a large proportion of it to go so fast, how do you expect to get much charge out of it?

Huh? I understand that any charging that occurs at this speed will be somewhat slow. But the issue is that it's actually charging the battery when it's in Save mode -- it shouldn't be doing that at all. Furthermore, its behavior in Save mode is identical to the behavior in Charge mode. And the way to stop it from charging the battery is...to put it in Normal mode.

So say I'm driving on the freeway and I've got 50% (8 bars worth) of battery I want to save for driving in the city. I estimate that I'll need 6-7 bars worth of battery before I can get to a charger. How do I keep this energy stored? Put it in Save mode, right? Well no...if I do that, it will actually keep charging it all the way up to 14-15 bars, if my speed remains continuously above 78 mph. I could use Normal mode, if I am sure my speed will remain above 78 mph the entire way there, but if traffic is such that I drop below that speed, it'll consume the battery power instead and I'll no longer have sufficient energy when I get there. The workaround is seemingly to use Normal mode whenever I go above 78 mph and Save mode below this speed, and keep switching between the two whenever I cross that speed threshold, which seems like a serious software flaw in this vehicle.

 

[kpetrov]

Littlescrote, he is saying exactly the opposite. He is complaining that in very high speed the SAVE is constantly charging the battery.

I can't confirm STS134 findings since never had the urge or necessity to push it over 125mk/h but probably over the observed threshold the engine produce excessive power that the computer find is better to be harvested even in Save mode.
Since the electric power is obviously not enough even in Save mode the engine is staying online all the time and the excess power if any is dumped in to the battery. Seems right to me.
The only think I don't understand is "Normal mode: ABOVE 78 mph/125 km/h generators and motors do nothing"!!! Absolutely nothing?
If that's correct there it is. Normal mode is your Save mode in high speed.

:lol: :lol: :lol: we were writing in the same time, same conclusion.

 

[STS134]

Littlescrote, he is saying exactly the opposite. He is complaining that in very high speed the SAVE is constantly charging the battery.

I can't confirm STS134 findings since never had the urge or necessity to push it over 125mk/h but probably over the observed threshold the engine produce excessive power that the computer find is better to be harvested even in Save mode.

I have little doubt that putting extra power into the battery improves the overall trip fuel efficiency. Since the car lacks a traditional gearbox and the RPM/wheel speed ratio is fixed, it cannot vary RPM while keeping power constant. If you are driving on flat terrain and do not require acceleration, this puts the car in an inefficient spot on the consumption map -- to the right and below the "sweet spot". Here's a typical consumption map:

The only thing it can really do is vary the load, i.e. power output, while keeping the RPM constant, which means using the generator to dump excess power into the battery. That's like moving upward on the above chart to a more efficient operating region. Except that's really irrelevant when the user has specifically told the car to keep the battery level where it is. Once that direct request from the user comes in, it should simply run less efficiently, regardless of the reasons why the user wants to do this (in my case, to avoid stressing the battery). Hence my original question: didn't Mitsu even test this stuff before pushing it out the door? I've seen this happen before, as my battery gained about 4 bars while in Save mode on another long trip. But I never fired up PHEV Watchdog before to confirm what I was seeing, or tried toggling the different modes while driving at high speed to see what would happen.

We're obviously aware of the hysteresis cycle that occurs when the car is on the freeway in Normal mode, where it will operate both engine + generators and charge the battery, then shut down the engine entirely and consume the power that it pushed into the battery. It does this because it's more efficient from a trip fuel consumption perspective to operate the engine in an efficient region, then shut it down entirely. But the issues here are:

1. It can't do a hysteresis cycle when the speed is continuously above 78 mph because the engine can't ever shut down, thus charging the battery continuously (and in my case, it did this to the extent of literally filling an empty battery halfway!)

2. It actually doesn't charge the battery in Normal mode, which is backwards. Normal mode, as far as I'm concerned, is basically telling the computer to pick the operating regime. If anything, Normal mode should do this, but Save mode should not.

 

[greendwarf]

Never noticed this when bombing down French auroroute to South of France at 80+mph (130kph) in my 2014 version - so may be later model/US specific. However, maximum speed limit in Japan is 75mph (120kph) so perhaps you are right, because the Japanese could not imagine anyone ever driving faster than this! :lol:

 

[kpetrov]

Littlescrote, he is saying exactly the opposite. He is complaining that in very high speed the SAVE is constantly charging the battery.

I can't confirm STS134 findings since never had the urge or necessity to push it over 125mk/h but probably over the observed threshold the engine produce excessive power that the computer find is better to be harvested even in Save mode.

I have little doubt that putting extra power into the battery improves the overall trip fuel efficiency. Since the car lacks a traditional gearbox and the RPM/wheel speed ratio is fixed, it cannot vary RPM while keeping power constant. If you are driving on flat terrain and do not require acceleration, this puts the car in an inefficient spot on the consumption map -- to the right and below the "sweet spot". Here's a typical consumption map:
The only thing it can really do is vary the load, i.e. power output, while keeping the RPM constant, which means using the generator to dump excess power into the battery. That's like moving upward on the above chart to a more efficient operating region.

Since you already know that the only thing it can really do (in fixed gear ratio) it to use the generator to dump excess power into the battery, why you have doubt that putting extra power into the battery improves the overall trip fuel efficiency? There isn't any other option.

Except that's really irrelevant when the user has specifically told the car to keep the battery level where it is. Once that direct request from the user comes in, it should simply run less efficiently, regardless of the reasons why the user wants to do this (in my case, to avoid stressing the battery). Hence my original question: didn't Mitsu even test this stuff before pushing it out the door? I've seen this happen before, as my battery gained about 4 bars while in Save mode on another long trip. But I never fired up PHEV Watchdog before to confirm what I was seeing, or tried toggling the different modes while driving at high speed to see what would happen.

We're obviously aware of the hysteresis cycle that occurs when the car is on the freeway in Normal mode, where it will operate both engine + generators and charge the battery, then shut down the engine entirely and consume the power that it pushed into the battery. It does this because it's more efficient from a trip fuel consumption perspective to operate the engine in an efficient region, then shut it down entirely. But the issues here are:

1. It can't do a hysteresis cycle when the speed is continuously above 78 mph because the engine can't ever shut down, thus charging the battery continuously (and in my case, it did this to the extent of literally filling an empty battery halfway!)

2. It actually doesn't charge the battery in Normal mode, which is backwards. Normal mode, as far as I'm concerned, is basically telling the computer to pick the operating regime. If anything, Normal mode should do this, but Save mode should not.

Regarding the second part I agree. If your observations are indeed correct then Normal and Save should act exactly the opposite way.
By my opinion since the engine can't be stopped at those speeds the excess power if any should be always dumped in to the battery regardless of mode selected until the BMU decide not to.
If Your main goal is to reduce the stress on the battery, how you achieve that in lower speeds outside the battery range? Save will cycle the the battery charge anyway.

 

[STS134]

Since you already know that the only thing it can really do (in fixed gear ratio) it to use the generator to dump excess power into the battery, why you have doubt that putting extra power into the battery improves the overall trip fuel efficiency? There isn't any other option.

I think you missed the part where I said I have "little doubt" that this is the case.

Regarding the second part I agree. If your observations are indeed correct then Normal and Save should act exactly the opposite way.
By my opinion since the engine can't be stopped at those speeds the excess power if any should be always dumped in to the battery regardless of mode selected until the BMU decide not to.
If Your main goal is to reduce the stress on the battery, how you achieve that in lower speeds outside the battery range? Save will cycle the the battery charge anyway.

Save mode does cycle the battery, but haven't you noticed how the hysteresis cycle is much smaller in Save mode than it is in Normal mode, when you have a depleted battery and it's down to 1 bar? Save mode actually prefers series mode much more than Normal mode, and tries to generate electricity as it's used, and runs the engine at whatever RPM is most efficient for generating that amount of power. I see it doing the hysteresis cycle when in Save mode primarily after I have to brake, when it shuts down the engine and then consumes the (small) amount of power that it regenerated. Then it turns the ICE back on. And in any case, the vast majority of the time I'm on the freeway, I do not have a fully depleted battery, so Save mode does protect the battery from being discharged at a very high C rate and decreasing its lifespan.

 

[kpetrov]

Save mode does cycle the battery, but haven't you noticed how the hysteresis cycle is much smaller in Save mode than it is in Normal mode, when you have a depleted battery and it's down to 1 bar? Save mode actually prefers series mode much more than Normal mode, and tries to generate electricity as it's used, and runs the engine at whatever RPM is most efficient for generating that amount of power. I see it doing the hysteresis cycle when in Save mode primarily after I have to brake, when it shuts down the engine and then consumes the (small) amount of power that it regenerated. Then it turns the ICE back on. And in any case, the vast majority of the time I'm on the freeway, I do not have a fully depleted battery, so Save mode does protect the battery from being discharged at a very high C rate and decreasing its lifespan.

What do you mean by "Save mode actually prefers series mode much more than Normal mode"?
If your engine is already running there is ONLY a series mode or the more efficient parallel mode over 65km/h.
Normal prefer pule el. propulsion, Save is ruining series or parallel mode in intermittent manner, Charge in constant manner.
Looking how to reduce the currents in an electric propulsion vehicle while driving fast is an lost cause for me.

 

[STS134]

What do you mean by "Save mode actually prefers series mode much more than Normal mode"?
If your engine is already running there is ONLY a series mode or the more efficient parallel mode over 65km/h.
Normal prefer pule el. propulsion, Save is ruining series or parallel mode in intermittent manner, Charge in constant manner.
Looking how to reduce the currents in an electric propulsion vehicle while driving fast is an lost cause for me.

I mean that if your speed is below 78 mph, Save mode will keep the system in series mode even during times that if it was in Normal mode, it would be running in Parallel mode and dumping extra power into the batteries. Save mode reduces the amount of hysteresis that occurs -- even if it's enabled when the battery is fully depleted.

 

[Amalia]

Hi all,

I am new here, I have my car since January bought from a Mitsubishi dealer, used car.
Lots of technical words here on the forum...I am a bit lost.
I had no home charging possibility so I charge it at the fast charge stations at the moment, 3 times so far. I noticed that the battery drains very fast, double fast actually with no AC or lights on.
When I connect the charging cable it shows that it starts to charge from 25% but my battery is completely empty and goes only to 80% and stops charging. So theoretically I have only a 55% charged battery. I thought that this car can run on a battery for about 28 miles. After I charge my battery it shows that I can run 16 miles. I drive about 5-7 miles (in the city, not highway) and it's empty.

I wrote to the dealer and he keeps telling me that after I have my home charging cable (normal power socket, as I have no driveway) the battery will charge better. The battery is consuming its power too fast! How a cable will change the faultiness of the battery?
I asked for a battery check but I had no answer.
Please advise, but ... not too many technical explanations as is Chinese for me (or should I say Japanese? )

 

[AndyInOz]

There's a few different things muddled together here.

1. IIRC Fast charging is limited to 80% to protect your battery. You can overcome this by unplugging and then starting the charge a second time.
(But it will damage your battery if you do this)
2. I can't think of any circumstances that would cause your battery to discharge faster when you turn off the air-conditioning and heating, but, if you are somehow disabling battery cooling or heating, that could cause your battery to behave differently.
3. The main factors that determine the amount of distance that you get from a charge are:
(a) The temperature of your drive battery;
(b) How fast you accelerate;
(c) Your top speed;
(d) The load you are hauling;
(e) Headwind; and,
(f) If you have stuck brakes (emergency brake or stuck calipers).

You can check for the last one by walking around the car after you arrived at your destination, and see if any of the wheels are hot.

 

[jaapv]

There's a few different things muddled together here.

1. IIRC Fast charging is limited to 80% to protect your battery. You can overcome this by unplugging and then starting the charge a second time.
(But it will damage your battery if you do this)
2. I can't think of any circumstances that would cause your battery to discharge faster when you turn off the air-conditioning and heating, but, if you are somehow disabling battery cooling or heating, that could cause your battery to behave differently.
3. The main factors that determine the amount of distance that you get from a charge are:
(a) The temperature of your drive battery;
(b) How fast you accelerate;
(c) Your top speed;
(d) The load you are hauling;
(e) Headwind; and,
(f) If you have stuck brakes (emergency brake or stuck calipers).

You can check for the last one by walking around the car after you arrived at your destination, and see if any of the wheels are hot.

This!

 

[greendwarf]

Amalia, you should find this helpful about charging etc.

https://www.electrifying.com/blog/knowledge-hub/10-charging-facts-that-every-electric-car-owner-should-know

 

[ThudnBlundr]

Have a look at Section H of Richi's FAQs. The rest of it is well worth reading too...