things that make the engine start in econ mode

V

victor_2019

Active Member
so it's been happening lately that in econ mode my engine starts, which didn't happen before.

this bothers me because I have a very short commute so even if the engine shuts off after 5 minutes, that's like half my morning commute.

it's happening when the battery is fully charged.

first times it happened I figured out that it was likely because I was setting cruise control on while on the street, before reaching the highway, with the battery fully charged. I figured that when the car needs to slow down in cruise control mode it needs the regen so if the battery is full it won't be able to slow down so it start the engine.

so I stopped using cruise control until I get tot he highway, and by that time I've used enough of the battery to re-enable regeneration braking, and the engine stopped turning on for a while (a week or two).

however, yesterday it did it again.

once again I was fully charged and this time I didn't use cruise control, however I was going somewhere else so I entered the highway right away with a full battery and accelerated in econ mode to highway speeds (normal acceleration, I didn't activate kickdown switch), and then I noticed the engine was on.

while looking at the fuel consumption gauge, it was sitting pretty much at zero the whole time but the engine was running. so I guess it was just running idle.

I specifically use econ mode because it doesn't turn on the engine, but normally before I enter the highway I've traveled a few kilometers so the battery is not at 100%.

is there a reason the engine would turn on at highway speeds with a battery very close to 100%?

I may have pressed the brake when entering the highway to merge with traffic, but that was with the brake pedal not cruise control. could this trigger the engine?

I want to figure out how to avoid turning on the engine since as I said, I usually have very short drives and my battery is always sufficiently charged, I don't want to burn gas for no reason.
 
Pressing the brake pedal can trigger the engine to run. The brake pedal also uses regen for stopping. If you hit the brake too hard, it will especially trigger the engine to run.

During the winter I never had 'false' engine starts: Now that I am not using the heater, there are more engine starts. On cold mornings, the heater may turn on (without me noticing), and it helps avoid the engine starts.

I have not had my engine start while at highway speeds, but I have had it start when I tap the brakes because the car in front of me had to slow on the entrance ramp.
 
victor_2019 said:
my engine starts, which didn't happen before.
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victor_2019 said:
this bothers me because I have a very short commute.

I usually have very short drives and my battery is always sufficiently charged, I don't want to burn gas for no reason.
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Sounds like you may operate in EV mode a lot and, if so, the ICE may possibly have entered fuel/oil maintenance mode and be running due to inactivity. If this seems likely, a good drive in HV mode made be enough to silence it for a while.
 
It sounds like your commute is short enough that you don't need to fully charge? If so you can use scheduled charging. It doesn't have a way to charge to a certain percentage, but with a little practice it's not hard to estimate how much time it takes to charge to whatever percent you want, like 90% or whatever.

As ClarityBill said during winter you may not have the problem or at least not as often.
 
ClarityBill said:
Pressing the brake pedal can trigger the engine to run. The brake pedal also uses regen for stopping. If you hit the brake too hard, it will especially trigger the engine to run.

During the winter I never had 'false' engine starts: Now that I am not using the heater, there are more engine starts. On cold mornings, the heater may turn on (without me noticing), and it helps avoid the engine starts.

I have not had my engine start while at highway speeds, but I have had it start when I tap the brakes because the car in front of me had to slow on the entrance ramp.
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Are you sure it's from pressing the brakes? I know the regen paddles will trigger the ICE if the car has too high of an SoC; otherwise, the car will default to friction brakes until the SoC drops below the threshold
 
AlAl said:
Are you sure it's from pressing the brakes? I know the regen paddles will trigger the ICE if the car has too high of an SoC; otherwise, the car will default to friction brakes until the SoC drops below the threshold
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Pressing the brake pedal is almost completely regen, as can be observed on the power display on the instrument panel while using the brakes to slow down. However we believe a small amount of friction brakes are blended in for smoothness, and also the last few mph before coming to a stop uses only friction brakes.

There is a theory that with full battery stepping on the brakes will use friction brakes, but I don't know if that has been confirmed.

But you are right the full battery regen ICE activation syndrome can occur using the paddles also.
 
AlAl said:
Are you sure it's from pressing the brakes? I know the regen paddles will trigger the ICE if the car has too high of an SoC; otherwise, the car will default to friction brakes until the SoC drops below the threshold
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Absolutely you can get the ICE from a full SoC with just the brake pedal. I'll get it maybe one in four trips depending how I leave the subdivision in summer. I never use the paddles. My pet theory is that in certain circumstances, it decides to "pop the clutch" to slow down, directly coupling the wheels to the engine. Then, once the engine has turned over, it has to run until it's warm.

It's annoying, but doesn't burn a lot of fuel, in my experience. I still try to avoid it.
 
Happens to me more in the winter. I am always using the A/C in the summer. This may prevent it. I found that turning on the heat in the winter lesson the incidence.
 
In my quest to drive my Clarity like a full on BEV as much as possible, I have been very careful to observe and mitigate the ICE runs. Since I take few out of town trips, I’ve only pumped 17.2 gal in 11,000+ miles. Here’s what I found.

1 The unintentional ICE starts seemed more frequent when the car was new but that could be to my growing understanding or maybe the battery aging.
2. With no downhill close to my home, I have been able to virtually eliminate the ICE runs for limited regen with full battery by more gentle braking over a longer distance as opposed to hard braking right at the stop sign or light.
3. After greatly reducing the ICE runs for the limited regen/full battery, the System Checks are only happening no more than once a month and don’t even cause me to loose a single bar on the gas gauge over a year. So not enough gas usage to worry about and I don’t begrudge the algorithm keeping the ICE happy and ready to run.
4. I’m not sure if pedal vs paddle slowing makes any difference. I’ve found that 1 or 2 chevron regen doesn’t start the ICE but 4 chevrons caused it to blink and the ICE came on. So now I think it’s how much you go over the limited amount of regen that triggers the ICE.
5. Every time my ICE has started on its own (not going past click, not selecting HV, not getting to 0 EV), it has always turned itself off. In the summer it’s within 2 min and longer in the winter.

So I’m calling this normal behavior and am happy with how my Clarity behaves. I’ve only had the HV range update done and build date is 11/17, purchased 2/18.
 
I've become good at knowing how long to charge my car using the Hondalink app so as start off my day with no more than 90% state of charge. My ICE never comes on even when using regen as long as I don't have it charged fully.
 
2002 said:
There is a theory that with full battery stepping on the brakes will use friction brakes, but I don't know if that has been confirmed.
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I can confirm that when the battery is full and I press the brakes, the power meter will not show any kind of power going back to the battery.

it will only start showing charging when I've driven a kilometer or so. and just braking with a full battery at 50-60 km/h will not start the engine.
 
victor_2019 said:
I can confirm that when the battery is full and I press the brakes, the power meter will not show any kind of power going back to the battery.

it will only start showing charging when I've driven a kilometer or so. and just braking with a full battery at 50-60 km/h will not start the engine.
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Your experience seems consistent with the theory. Although I don't think we know why the friction brakes aren't enough in cases of normal braking going down a hill or coming to a stop and it sometimes has to start the engine to assist with braking in some still mysterious way. Maybe the friction brakes on Clarity are sized lighter than they would ordinarily be on a 4,000 lb car?
 
2002 said:
Your experience seems consistent with the theory. Although I don't think we know why the friction brakes aren't enough in cases of normal braking going down a hill or coming to a stop and it sometimes has to start the engine to assist with braking in some still mysterious way. Maybe the friction brakes on Clarity are sized lighter than they would ordinarily be on a 4,000 lb car?
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My working theory is that it's speed-related. At certain SoC, certain speed ranges, and certain levels of braking (paddle or pedal), then the car decides that it can "pop the clutch" to slow down. Then, once the engine has turned over, it will run until warm.

The speed component is one that I've not seen mentioned before on the forum. Since "gear mode" will only occur at certain speeds and loads, it seems possible that this behavior could have a speed component. Especially since the easiest way to engine brake is to engage gear mode (pop the clutch).

I've been trying to note my speed when this occurs, but it doesn't happen often enough for me to have a feel yet: I've come to a stop at the light. What's that noise? Sigh. How fast was I going when I started braking?
 
I have TorquePro logging most of the time, and was hoping I could shed light on this since the engine came on while my daughter was driving with me yesterday. I had turned off the AC, and *thought* the engine started when she braked fairly hard from 40 MPH for a light about 1/2 mile from our house. However, looking at the log it actually came on 20 seconds before that, while cruising at ~38 MPH. She doesn't *think* she pressed past the detent, and it came on a full 10 seconds after she had accelerated onto the main road so I don't think that was it either.

The power meter stayed white the whole rest of the 30 minute drive, but the engine stopped after 4 minutes (when the coolant reached 160 degrees) and never came on again and the EV light was on, including through dropoff without turning the car off and the freeway part of my commute. I've seen that before, and it could be the "System Check", but the manual implies the blue line will appear again when the system check is complete. Other times the blue line has reappeared after 10 minutes or so (with the engine off and EV light on before that) -- perhaps there are occasional system checks that don't require the engine on but take longer. Or there's a bug in the display logic.

I will look through my logs later to see when the engine had last come on before yesterday.
 
Since I bought in January I was doing my daily 40 mile commute to-from work almost entirely on EV mode (economy setting driving through streets). Every now and then I had the engine starting, specially after leaving work with a fully-charged battery. Then I did a long trip on HV mode like 6 weeks ago. No more "spontaneous" ICE ever since.
 
JCA said:
I have TorquePro logging most of the time, and was hoping I could shed light on this since the engine came on while my daughter was driving with me yesterday. I had turned off the AC, and *thought* the engine started when she braked fairly hard from 40 MPH for a light about 1/2 mile from our house. However, looking at the log it actually came on 20 seconds before that, while cruising at ~38 MPH. She doesn't *think* she pressed past the detent, and it came on a full 10 seconds after she had accelerated onto the main road so I don't think that was it either.

The power meter stayed white the whole rest of the 30 minute drive, but the engine stopped after 4 minutes (when the coolant reached 160 degrees) and never came on again and the EV light was on, including through dropoff without turning the car off and the freeway part of my commute. I've seen that before, and it could be the "System Check", but the manual implies the blue line will appear again when the system check is complete. Other times the blue line has reappeared after 10 minutes or so (with the engine off and EV light on before that) -- perhaps there are occasional system checks that don't require the engine on but take longer. Or there's a bug in the display logic.

I will look through my logs later to see when the engine had last come on before yesterday.
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Mine behaves exactly like this. For awhile I thought I could avoid the regen startup if I preconditioned the car while not plugged in before my drive, but that method failed me last week too. I’ve decided to just let the car do its thing and stop worrying about it.

With your meter you probably have monitored the RPMs after the regen startup. I can only monitor the estimated range, but after a regen startup it seems to mostly us EV miles even though the engine is running. Is it just idling until it gets up to temp?
 
How can regen be turned on/off at the whim of the car? Asking half out of academic curiosity in case anyone can provide an accessible explanation.

The traction motor is permanently connected to the wheels. As long as the wheels are spinning, so is the traction motor. This consumes energy during acceleration, and produces energy during deceleration. The energy it produces needs to go somewhere. It's fed back into the battery when it can safely accept charge.

But when the battery SOC is too high, I was under the impression the Clarity spun up the generator motor. In this scenario, the traction motor is acting as a generator, and the generator motor is acting as a motor. The generator motor is permanently connected to the ICE, so the ICE starts when the generator motor is spun up to serve as the load for the energy produced by the traction motor.
 
r1ptide64 said:
How can regen be turned on/off at the whim of the car? Asking half out of academic curiosity in case anyone can provide an accessible explanation.
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The traction motor is controlled by an inverter which decides what the motor is doing. The motor can accelerate, decelerate or coast, but all this is controlled by the inverter.

The car uses a permanent magnet motor which has a rotor containing magnets and a stator containing windings or coils, which are connected to the inverter.

If the inverter doesn't do anything the motor is coasting.

If the inverter creates a magnetic field in the stator coils then the rotor wants to align with that field which creates a force in the rotor (motor torque).

If the torque is in the same direction as the movement of the motor, then this is called motoring. It will create acceleration and will consume power.

If the torque is opposing the motor movement then this is called generating. It creates braking force and generates power which must go somewhere.

But the inverter doesn't have to create a field in the winding. The field is created by current flowing in the winding, if there is no current then there is no field.

The rotating rotor will induce a voltage in the stator windings but if the inverter doesn't switch the semiconductors on then there will be no current flowing.
 
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