Poll: Unexpected ICE Turn-ons with full battery?

[M.M.]

Based on a couple of other threads here with reports of Claritys unexpectedly turning on the gasoline engine when the battery is full, I'm hoping to gather a little more data about when this is happening. Some times it could be normal part of trying to do engine braking when the battery can't absorb any more regen, but reports seem to be indicating that the car is generating energy with the ICE when it shouldn't.

Replies appreciated! If you're one of the people who has had the car turn on the ICE with a full battery, if you can give specific detail as to what sort of drive this happens on it would be additionally useful data. (For example, "Totally flat residential road with stop signs.", "3 miles of slight downhill highway", "Steep 5 mile downhill at 35mph".)

 

[KentuckyKen]

M.M thanks for starting the poll and sharing some great info. Here are my details.
ICE came on twice immediately after a full charge just 4 doors down from my house. Slightly downhill, 70sF, no non-motive drain on battery, EV range in the 60s. Accelerated just a little to get going up to 25, then let off for curve, very limited regen (barely in the green and pedal doesn’t add any more) and ICE came so quietly that w windows up I only knew it was on due to energy display. Ran at what I would call a fast idle. Power meter turned white. Stopped car, turned off and was back in EV on restart. (Probably should have let engine warm up)
Third and forth times were about 1 mile from full charge leaving home and occurred after full braking (just short of ABS activation) due to cars pulling out in front of me. Same ICE behavior and conditions as above but these two times I let car do it’s thing. ICE ran for just a few minutes, turned off and EV came back by itself. Third time I pulled over and ICE exhaust manifold was hot but top and sides of engine were not. Fourth was at hwy speeds and ICE went on/off/on/off with power modes switching frequently. Still only ran for a few minutes (maybe 4-5).
I drive pretty conservatively (accel only to 12:00 on power meter) and all this occurred within first 1,700 miles (2months) of ownership. Only have had 1 trip over 50 miles and have only used 2 gal of gas. No angry bees/high revs ever. Have only depleted battery to around 2 bars on the 1 hwy trip (let car select HV mode) with no loss of power or high revs. All miles w just slight inclines. Also note that w full charge and no non-motive drain on battery, I have to drive about 5 miles to get regen to become normal again.

I’m assuming these instances were due to algorithm not allowing fully charged battery to accept any regen charge and somehow ICE is being used to brake and/or protect battery from over charge???? More info may answer this.

 

[PHEV Newbie]

ICE has never turned on in Econ mode but has come on in normal mode when I hit the accelerator a bit more than usual but without going pass the detent. You have to have a very light foot to keep the ICE off in normal or sport mode.

 

[Sandroad]

My ICE has started and run at idle with the HVAC off, outside temp at about 60F, with a full battery, in Econ mode, while driving slowly down my level driveway and residential street. Doesn't really fit any of the poll scenarios. I have no idea why it turns on by itself. After a very short while, it turns off and the car goes into EV mode for the rest of the trip.

 

[M.M.]

...ICE came so quietly that w windows up I only knew it was on due to energy display. Ran at what I would call a fast idle. Power meter turned white. Stopped car, turned off and was back in EV on restart.

It sounds like you quite definitively confirmed the ICE was running, but as a much more general note I thought I should comment that it's at least theoretically possible for the display to be lying about the ICE (I know early Volts would show the ICE running in some full-battery states even though it was not due to the display algorithm getting confused). Not saying this the case with the Clarity, just that it's something to keep in mind.

ICE has never turned on in Econ mode but has come on in normal mode when I hit the accelerator a bit more than usual but without going pass the detent. You have to have a very light foot to keep the ICE off in normal or sport mode.

I learned from the manual recently that the sort of solid/dashed line below the curve of the power gauge shows you where the car will kick in the ICE. So in Econ mode the dashed line starts over on the far right at the white point, which is the detent on the pedal; when I checked Normal mode it looks to be somewhere around straight up, Sport even farther to the left, and in HV mode it will move around constantly depending on speed and battery state of charge.

Personally I'd much rather it was always at the detent, but at least looking at the dashed line makes it feel less random. (Actually, I'd really rather it was more like the Volt and refused to turn the ICE on at all unless in HV mode, but oh well.)

Doesn't really fit any of the poll scenarios.

True; maybe I should have put a third option for "pleasantly warm outside" on there. Your case certainly sounds like a bug, since there's absolutely no reason for the ICE to come on if there's no regen happening, even if climate control is off.

 

[M.M.]

It occurs to me one thing that might theoretically be a factor in this situation is if the Clarity has an equivalent to the Volt's "maintenance" ICE run. In that car, if you drive pure EV all the time, after about 1 month it will tell you it needs to exercise the ICE for about 10 minutes and gives you the option to cancel if it's going to be a short drive or whatever.

I haven't had my Clarity long enough to know whether it's going to do this or not, but if there's a similar exercise mode in the car but it gives the driver no indication, the ICE come on at unexpected full-battery times. That would only make sense if it happened on an infrequent, regular schedule, like once a month. Seems like it would be less likely anyway, since all it takes is being overly aggressive on the accelerator once to get the ICE running for several minutes.

 

[AGarg]

I learned from the manual recently that the sort of solid/dashed line below the curve of the power gauge shows you where the car will kick in the ICE. So in Econ mode the dashed line starts over on the far right at the white point, which is the detent on the pedal; when I checked Normal mode it looks to be somewhere around straight up, Sport even farther to the left,

Slightly off topic but responding to the above comment from M.M. In my case, the length of the Blue solid line is same (far right) for both Econ and Sport mode (picture attached). I drive in Sport mode all the time and I'm always able to keep the car in the EV mode even when I accelerate fast. Do you all have a shorter blue solid line in Sport mode?

Also, yesterday the ICE started for no reason whatsoever, at full charge in Econ mode and the solid blue line turned to a dashed white line and the power flow monitor showed power being drawn from the ICE. The EV indicator turned off. I continued to drive (HV range dropped by a few miles) but after 5 minutes the EV indicator came back on and the power flow monitor showed the car drawing power from the battery. However, the solid blue line never returned and the gauge continued to display the dashed line all the way for the entire 180 degrees.

The whole system needs to be re-tested and fixed by Honda as it's not very stable/consistent.

 

[KentuckyKen]

It sounds like you quite definitively confirmed the ICE was running, but as a much more general note I thought I should comment that it's at least theoretically possible for the display to be lying about the ICE (I know early Volts would show the ICE running in some full-battery states even though it was not due to the display algorithm getting confused). Not saying this the case with the Clarity, just that it's something to keep in mind.

M.M., I can be sure when the ICE is on because I have installed an inductive pick up hour meter and check it at destination whenever I see the display light up the engine icon. So far it hasn’t given a false positive indication.

 

[insightman]

I'm still skeptical that running the engine can use up unwanted electricity. Normally, when the Clarity PHEV decelerates, the traction motor switches to generator mode and sends electricity to the battery. However, that cannot happen when the battery is fully charged.

When the Clarity PHEV is decelerating with a fully charged battery:

• The traction motor is not using electricity from the battery (or the starter motor/generator) to accelerate the car
• The traction motor is not generating electricity to recharge the battery
• The starter motor/generator (powered by the engine) is not generating electricity to recharge the battery

The starter motor/generator can consume a little battery power to start the engine, but then what happens if the deceleration continues for a long time, such as when the car is going down a long hill? What can the engine do to use up unwanted electricity?

 

[M.M.]

I'm still skeptical that running the engine can use up unwanted electricity. [...] The starter motor/generator can consume a little battery power to start the engine, but then what happens if the deceleration continues for a long time, such as when the car is going down a long hill? What can the engine do to use up unwanted electricity?

What the Clarity actually does I can't say. I have neither the detailed knowledge of its drivetrain nor that of the software that runs it necessary to understand that.

But the ICE most certainly could, at least in theory, be used to use up unwanted energy.

I assume you're familiar with engine braking. By removing most of the fuel flow into an ICE, the internal friction and passive air compression caused by it being spun uses energy, which (since the engine is mechanically linked to the wheels) slows the car. Essentially the kinetic energy is being converted into heat that is either dumped into the radiator or blown out the exhaust in the form of compressively-heated air.

So the Clarity has two different theoretical means of using the ICE in order to decelerate (I say theoretical, because in practice I have no idea which if either of these it does):

1. It uses the mechanical transmission to link the wheels to the ICE, puts the CVT at the correct point for the desired amount of decelerative force, and uses traditional engine braking to dissipate energy.
2. Instead of putting a load on the starter motor/generator that's connected to the ICE, thereby pulling energy from the ICE and converting it to electricity, it actually pumps energy into that generator, which forcefully spins the ICE and generates engine braking on the generator. This would be akin to running it as a starter for an extended period of time. It could then do regenerative braking with the main drive motor and send whatever energy it generated into the generator to waste in the ICE. This sounds nuts to me practically speaking, but technologically it's possible.

In either of these cases, note that the ICE needs to be turned on and engaged, but very little fuel should be going to it. As I understand it, the Prius Prime does roughly #1 above, while the Volt does neither--it uses the pair of motor/generators and the transmission to essentially waste energy in the electric motors, which is dumped as heat into the motor cooling system.

At this point I have no idea what choices Honda made regarding engine braking, only what they might have done. But any answers to this poll indicating that the ICE came on with a full battery with little in the way of downhill going on indicate that either the ICE is starting for some entirely unrelated reason (software bug regarding acceleration, unannounced exercise routine, etc) or that there's a programming error in the regen routine that is causing it to be way too aggressive with when it starts.

 

[M.M.]

M.M., I can be sure when the ICE is on because I have installed an inductive pick up hour meter and check it at destination whenever I see the display light up the engine icon. So far it hasn’t given a false positive indication.

That's even more thorough than I thought. Just to be clear, though, I wasn't doubting your analysis at all, just commenting more generally that a display bug isn't impossible.

 

[KentuckyKen]

What the Clarity actually does I can't say. I have neither the detailed knowledge of its drivetrain nor that of the software that runs it necessary to understand that.

But the ICE most certainly could, at least in theory, be used to use up unwanted energy.

I assume you're familiar with engine braking. By removing most of the fuel flow into an ICE, the internal friction and passive air compression caused by it being spun uses energy, which (since the engine is mechanically linked to the wheels) slows the car. Essentially the kinetic energy is being converted into heat that is either dumped into the radiator or blown out the exhaust in the form of compressively-heated air.

So the Clarity has two different theoretical means of using the ICE in order to decelerate (I say theoretical, because in practice I have no idea which if either of these it does):

1. It uses the mechanical transmission to link the wheels to the ICE, puts the CVT at the correct point for the desired amount of decelerative force, and uses traditional engine braking to dissipate energy.
2. Instead of putting a load on the starter motor/generator that's connected to the ICE, thereby pulling energy from the ICE and converting it to electricity, it actually pumps energy into that generator, which forcefully spins the ICE and generates engine braking on the generator. This would be akin to running it as a starter for an extended period of time. It could then do regenerative braking with the main drive motor and send whatever energy it generated into the generator to waste in the ICE. This sounds nuts to me practically speaking, but technologically it's possible.

In either of these cases, note that the ICE needs to be turned on and engaged, but very little fuel should be going to it. As I understand it, the Prius Prime does roughly #1 above, while the Volt does neither--it uses the pair of motor/generators and the transmission to essentially waste energy in the electric motors, which is dumped as heat into the motor cooling system.

At this point I have no idea what choices Honda made regarding engine braking, only what they might have done. But any answers to this poll indicating that the ICE came on with a full battery with little in the way of downhill going on indicate that either the ICE is starting for some entirely unrelated reason (software bug regarding acceleration, unannounced exercise routine, etc) or that there's a programming error in the regen routine that is causing it to be way too aggressive with when it starts.

Just had a thought regarding these 2 possible scenarios. In the first, if the mechanical linkage is used, would we see the gear indicator light up like it does at hwy speeds when physical linkage is implemented?
I think one of M.M.’s scenarios must be happening based on all the posts. When it happens mostly on a full charge and seems to happen too frequently to be a System Check, then it must be doing what we assume to be braking/battery protection.

 

[M.M.]

...would we see the gear indicator light up like it does at hwy speeds when physical linkage is implemented?

I've wondered that myself and was assuming that somebody would have noticed at this point, but maybe it's just that no one uses that cluster setup or pays attention to it. If those who are also interested and having unexpected behavior could pay attention that would be interesting to know.

When it happens mostly on a full charge and seems to happen too frequently to be a System Check, then it must be doing what we assume to be braking/battery protection.

I'm not willing to rule this out for at least some fraction of the reports, in part because it seems to be so erratic. If it were simply an overly aggressive battery protection routine, those who see it should see it every time they drive. The routine should be deterministic--the battery is always at the same state of charge when unplugging, and your route to work in the morning is the same, and the way you drive is going to be the same, so aside from traffic and outdoor temperature if it happens once it should happen every time.

If it's a bug being triggered by, say, some particular regen rate at above some particular state of charge--which sounds quite similar to your "slam on the brakes shortly after leaving home" case, but doesn't explain a bunch of other situations--then it would be more erratic, but that doesn't explain a bunch of other cases.

So if in addition to those the ICE has a fairly short exercise period then those who never use HV mode or are lead-footed enough to kick in the ICE for power might have it turning on once a week, or once a month, or whatever, which would seem totally random if there is no user indication. Of course, then you'd expect even more people to have it happen, and on uphills, so maybe not...

(Aside: In case anyone is wondering why I seem to be analyzing this so obsessively, I'm a control systems programmer for power systems, and spend a significant fraction of my workweek when I'm not working on my own stuff trying to figure out what someone else's code is doing wrong so I can either tell them to fix it, or work around it.)

 

[Viking79]

Happened to me today as well, reeks of a bug. I say that as it never exited that mode on a 20 min 10 mile drive, and said EV despite no blue bar. It acted like hybrid.

Interesting was I could put it in HV mode and use it all electric if I kept it in the short blue bar, but returning to Econ and it did the same thing. Started full charge. Cool day around 53 F, raining, auto heat and seat warmer. Engine started when I was braking.

Seeing it again today and it makes me recall that I saw this once during winter but didn't think anything of it since it was cold.

 

[KentuckyKen]

Here is another data point. 5th ICE:
Left home w full charge. Day, 88F, a/c set to 70. 2 miles from home on a medium downhill applied brakes (no regen) to slow down from 45 to 20 with moderate braking and ICE came on. Only stayed on for 1-2 min and power bar turned all white (dashed and solid same as previous blue). When ICE went off, EV and Econ were on but power bar stayed white with ICE not coming back on for remainder of trip. HV range went down 2 miles. Upon restart hours later, blue power bar back. Note that even w white power bar, when ICE turned off it drove like it was in EV mode. No ICE, no high revs.
All this occurred 2 days, 1 charge and 11 miles from previous ICE “unexplained” start #4 previously posted, so that sort of rules out a System Check in my mind.
Only common factors in all five instances seem to be immediate prior full charge (HV range in the 60s) and braking. About half within 300 ft of leaving home and half within 2 miles.
Never occurs when battery guage is less than all 20 bars.

 

[Kestrel]

It has happened to me five or six times now, each time in the morning after charging to full overnight. Temps generally in the low 60s F, but once a little colder and once a little warmer.

Exit my garage with a full charge. Slight downhill for about 2/10 of a mile to a stop sign, with several cars in front of me so lots of braking. Flat for <1/10 mile to another stop sign, still stop and go. Then about 1/2 mile, steep downhill between 30 and 35 mph, and it pops out of EV in that stretch. It has happened when I'm using only the brake pedal and when I'm using the paddles first, then adding the brake. From there, I head uphill and then onto the freeway. I cannot get it to go back into EV without pulling over and turning off the car--but doing that has solved it each time.

 

[KentuckyKen]

It has happened to me five or six times now, each time in the morning after charging to full overnight. Temps generally in the low 60s F, but once a little colder and once a little warmer.

Exit my garage with a full charge. Slight downhill for about 2/10 of a mile to a stop sign, with several cars in front of me so lots of braking. Flat for <1/10 mile to another stop sign, still stop and go. Then about 1/2 mile, steep downhill between 30 and 35 mph, and it pops out of EV in that stretch. It has happened when I'm using only the brake pedal and when I'm using the paddles first, then adding the brake. From there, I head uphill and then onto the freeway. I cannot get it to go back into EV without pulling over and turning off the car--but doing that has solved it each time.

Kestrel, similar conditions do it for me too. How long does your ICE stay on? Next time let it go and check if it goes off after a few min. Mine does this and power bar stays white but EV/Econ is on and car drives on battery as usual. So I quit pulling over and restarting.
Would appreciate if you would try this and post what happens so we can see if this is common.

 

[KenG]

My Car must be broken.... lol... my Ice never comes on?


Sent from my iPhone using Inside EVs

 

[Kestrel]

Kestrel, similar conditions do it for me too. How long does your ICE stay on? Next time let it go and check if it goes off after a few min. Mine does this and power bar stays white but EV/Econ is on and car drives on battery as usual. So I quit pulling over and restarting.
Would appreciate if you would try this and post what happens so we can see if this is common.

I will try that next time it happens. I haven't just let it go, since I'd read about this happening before I experienced it, and knew I could get it back into EV if I restarted the car. The first time I drove about 5 miles until I could pull over at a rest stop, and in that time the EV light did not come back on and the power bar was all white. Since then, I've stopped before getting on the freeway, rather than letting it run.

I will report back after it happens again.

 

[KentuckyKen]

Happened to me today as well, reeks of a bug. I say that as it never exited that mode on a 20 min 10 mile drive, and said EV despite no blue bar. It acted like hybrid.

Interesting was I could put it in HV mode and use it all electric if I kept it in the short blue bar, but returning to Econ and it did the same thing. Started full charge. Cool day around 53 F, raining, auto heat and seat warmer. Engine started when I was braking.

Seeing it again today and it makes me recall that I saw this once during winter but didn't think anything of it since it was cold.

Viking, did the ICE turn off during your trip?
Mine turns off but the white does not turn back to blue. Despite that it always drives fully on battery with no ICE restart despite the power bar not returning to blue until I restart at destination. See if yours does this next time and post result. So for me ICE turns off and I drive in EV mode just with a white power bar.