Strange ICE behavior

[Rajiv Vaidyanathan]

I think this may have something to do with the problem reported by @bobcubsfan in another thread, but maybe not.

Several exciting things happened to me and my Clarity last week.

1. My EV range hit 50 miles for the first time ever. I found this very exciting (as background, I live in Duluth, MN and consistently got EV ranges in the low to mid 20s in my first several months of ownership).

2. Last week, with early morning temps in the high 30s (daytime temps in the low 60s), my ICE came on when I pulled out of my garage. My battery was fully charged as usual (see image below).


3. The ICE frustratingly stayed on for my entire drive to work (only a few miles) just like it was winter again.


4. Strangely, even after I came to a complete stop, and the engine was off (I couldn't hear it), the bar on the speedometer stayed white instead of turning to blue. This happened again two days later. Additionally, even though temps have actually been WARMER (in the 60s regularly), I have never hit 50 miles of EV again. So, it's not just ambient temps that affect it. See engine off but only white bar in picture below.


So, what does this mean (car has acted normal for the last two days)?

1. Why did ICE suddenly turn on and stay on?
2. Why no EV driving even when fully charged?
3. Why didn't EV capability come back on when fully charged and stationary?
4. What are all the factors that affect EV range beyond ambient temperature?

I'm finding both my EV and HV range to be extremely accurate. But then again, I haven't put gas in for a few months.

- Rajiv

 

[AGarg]

I have seen the ICE turn on when the battery is fully charged, the car is in Econ/EV mode, and the deceleration (minus) pedal is pressed. It's as if the battery cannot take anymore charge and the system defaults to ICE. I know it's weird but I am able to reproduce it consistently.

 

[bobcubsfan]

Total bunk. This "behavior" happens sporadically. With fully charged battery, sometimes ICE will come on at first stop sign about .3 miles from home. But not always. Has not done it for several days. But, stay tuned…

 

[KentuckyKen]

Total bunk. This "behavior" happens sporadically. With fully charged battery, sometimes ICE will come on at first stop sign about .3 miles from home. But not always. Has not done it for several days. But, stay tuned…

Not total bunk, Bob. Many of us have found AGarg’s scenario of ICE on when battery can’t take any more charge to be very plausible. Is it the only reason for ICE on for no apparent reason (like hills/max acel) besides the occasional System Check? Probably not, but it is a valid observation. May not happen every time, but for me I notice almost no regen taking place in this scenario so it seems a good explanation.
Also many have observed that when the ICE comes on it will not go off until it reaches a certain temp and EV mode will not come back without restarting.
As with any brand new application of tech, we are all still learning the ins and outs of the Clarity. As more and more post their observations we get a better understanding of what’s going on.
Please give us the details of the next time your ICE comes on and we’ll all try to help figure it out.

 

[bobcubsfan]

Sorry. What I meant was the behavior of the Clarity's computer is total bunk. This simply should never happen, period.

 

[Viking79]

Does this only happen charging over 120 V? I wonder if the car charges more over 120 V. Someone mentioned they usually saw 15 kwh from the wall with 120, don't think I have ever seen more than 14.5 kwh from the wall over 240 V. I don't think this would be the case, but trying to think of differences with why my wife has never seen this. She charges 240 V and burns gas regularly.

 

[bobcubsfan]

Only charging with 240v. No gas burned except for trip to Santa Barbara in early March. Oh, ICE burned some when it came on on its own.

 

[KentuckyKen]

Sorry. What I meant was the behavior of the Clarity's computer is total bunk. This simply should never happen, period.

No prob. I understand. Hopefully with more information on future occurrences we can figure it out.
I agree, Honda released the software before it was ready for prime time. Kinda makes us unpaid beta testers for Honda.

 

[Viking79]

Thanks, so unlikely tied to charging voltage, could be how frequently ICE is used. Hope we find more from Honda.

 

[Kendalf]

Does this only happen charging over 120 V? I wonder if the car charges more over 120 V. Someone mentioned they usually saw 15 kwh from the wall with 120, don't think I have ever seen more than 14.5 kwh from the wall over 240 V. I don't think this would be the case, but trying to think of differences with why my wife has never seen this. She charges 240 V and burns gas regularly.

Charging over 120V is slightly less efficient than over 240V, so that can account for the difference in power draw (all else being equal). This study showed Level 1 charging efficiency of 83.8% vs 89.4% for Level 2.

Also, if your EVSE allows changing the charge current, then it's possible that charging at a lower current may actually recharge the battery more than at a higher current. At least that's the case for small battery charging (eg. AA & AAA batteries) as the charger uses the voltage reading to determine when the battery is "full". Smaller currents while recharging cause smaller incremental changes to the voltage reading so the charger may continue charging the battery for awhile longer at the lower current level before it actually registers that the voltage is high enough to indicate that the battery is full.

 

[megreyhair]

I have similar issue. I floored the pedal too much and ICE kicked in while the engine was cold. It would turn itself off when the car was completely stopped and would kicked in again when the car started rolling. It did went back to EV mode after like 10 mins.

 

[Viking79]

@megreyhair That is normal if started by strong acceleration, it will run until fully warm, which is about 10 mins. Does this to reduce engine wear and tear.

 

[bfd]

It's normal behavior for a PHEV. When the battery has no more capacity to hold more electrons (according to its own algorithm, anyway) it "boils off" by defaulting to ICE. Happened ALL the time in the PriusPHEV. Some owners complained that because they had downhill travel out of their driveway, they were always getting kicked into HV mode after leaving home. Annoying, yes, but apparently a normal outcome of trying to put more electrons into a battery that's already full. Now, some of the other random firing of ICE should probably be explained in some white paper by Honda so that PHEV owners know what to expect from the Clarity PHEV system's "normal operating parameters".

 

[Kendalf]

Some owners complained that because they had downhill travel out of their driveway, they were always getting kicked into HV mode after leaving home.

This is why recently I've started setting the timer in my EVSE to recharge up to about 95-97% overnight so that the ICE doesn't get called on when I go down a slight incline after I leave the house.

 

[bobcubsfan]

It's normal behavior for a PHEV. When the battery has no more capacity to hold more electrons (according to its own algorithm, anyway) it "boils off" by defaulting to ICE. Happened ALL the time in the PriusPHEV. Some owners complained that because they had downhill travel out of their driveway, they were always getting kicked into HV mode after leaving home. Annoying, yes, but apparently a normal outcome of trying to put more electrons into a battery that's already full. Now, some of the other random firing of ICE should probably be explained in some white paper by Honda so that PHEV owners know what to expect from the Clarity PHEV system's "normal operating parameters".

Why doesn't happen all the time? Full charge. Leave home. Stop at corner. Stop again. Stop again. Sometimes ICE comes on, sometimes not. Inconsistent behavior.

 

[M.M.]

I haven't observed this behavior (although my ICE did come on a couple of times when sitting in park for a short period with plenty of battery--I suspect it was climate control related, since I haven't seen it happen since the weather got warmer). I can, however, offer a bit of technical commentary:

Also, if your EVSE allows changing the charge current, then it's possible that charging at a lower current may actually recharge the battery more than at a higher current. At least that's the case for small battery charging (eg. AA & AAA batteries) as the charger uses the voltage reading to determine when the battery is "full".

This is not accurate--a Ni-MH AA battery on a consumer charger has little to do with a multi-kWh Li-ion battery pack with active temperature management. Even a good AA/AAA charger will allow you to set the charge current to balance charge rate with total capacity, and the charge scheme with a large Li-ion pack is much more nuanced than that. Large battery packs with fast-charge capability (think 50kW Tesla chargers) generally charge at a high rate up to a point, then reduce near the top to charge fully, although if the Clarity stops far enough below 100% even that may not be necessary. And running at the max-possible 7.5kW charge rate, that's still less than a C2 charge rate on the Clarity's battery pack, which is plenty slow.

Bottom line, it's highly unlikely there's a difference between a 120V and 240V charge in terms of total capacity, and even if there was it would probably be too small to notice.

I have similar issue. I floored the pedal too much and ICE kicked in while the engine was cold. It would turn itself off when the car was completely stopped and would kicked in again when the car started rolling. It did went back to EV mode after like 10 mins.

This is unrelated, almost certainly by design, and makes some sense. Once the ICE has started for the first time on a drive, the Clarity's management system wants it to run for a while. This probably has to do with lubrication or temperature cycling or something. So once you've dropped out of EV mode due to hard acceleration, it will keep the engine on for a while (I think closer to 5 minutes, but could be as much as 10).

What other people are describing here is quite different.

It's normal behavior for a PHEV. When the battery has no more capacity to hold more electrons (according to its own algorithm, anyway) it "boils off" by defaulting to ICE.

This makes no sense to me whatsoever in a PHEV from an engineering standpoint. If the ICE is on, it is generating energy. That energy can go to the battery or the wheels, but there is energy going into the system that wouldn't be if the ICE was off. If the ICE is off, all energy is coming from the battery pack. Computers, power steering, power to move the car forward, climate control, etc.

So if you want to burn off energy in the battery pack, the last thing you want to do is turn on the ICE. You want it off, so you're consuming as much as possible.

More to the point, the only time at which there would be "excess" energy going into the battery pack is if you live at the top of a hill and charge fully before driving down the hill. There is overhead, but at some point the regenerative braking has put enough energy into the battery pack that it's not a good idea to add more.

The solution in this case would be for the car to stop regenerative braking. Which it can do--just change the pedal algorithm so it's only using the calipers, and disable the regen paddles. Again, though, starting the ICE would have the exact opposite effect--you now have an ICE hooked to a generator adding more energy, which you don't want. It should, if anything, refuse to start the ICE for the safety of the battery pack in that situation.

In a Clarity at highway speeds the ICE can be linked mechanically to the wheels, but even then all it's doing is reducing the draw on the battery. It could theoretically do engine braking with the ICE and the transmission, but it's a heck of a lot easier to just use the calipers.

 

[Jaketesla]

I agree with M.M. In the morning when I leave with a full battery I see that the needle doesn't go into the "charge" zone for the first 2 or 3 stops but the ICE never starts. If the battery can't regen the car uses the mechanical brakes.

 

[Kendalf]

This is not accurate--a Ni-MH AA battery on a consumer charger has little to do with a multi-kWh Li-ion battery pack with active temperature management... Bottom line, it's highly unlikely there's a difference between a 120V and 240V charge in terms of total capacity, and even if there was it would probably be too small to notice.

I figured there would be differences, but wanted to throw the idea out there still. I do most of my overnight charging at 240V & 10A, the lowest current allowed by my EVSE.

This makes no sense to me whatsoever in a PHEV from an engineering standpoint. If the ICE is on, it is generating energy. That energy can go to the battery or the wheels, but there is energy going into the system that wouldn't be if the ICE was off.

There has to be some engineering sense to this for both Honda and Toyota engineers to design the system this way. As mentioned by @bfd this behavior was commonly observed in the plug-in Prius. See this thread and this one from PriusChat for examples.

So if you want to burn off energy in the battery pack, the last thing you want to do is turn on the ICE. You want it off, so you're consuming as much as possible.

But an ICE can dissipate energy as heat, even if no energy is going into the generator or the wheels, and that seems to be how the system is designed.

More to the point, the only time at which there would be "excess" energy going into the battery pack is if you live at the top of a hill and charge fully before driving down the hill. There is overhead, but at some point the regenerative braking has put enough energy into the battery pack that it's not a good idea to add more.

The solution in this case would be for the car to stop regenerative braking. Which it can do--just change the pedal algorithm so it's only using the calipers, and disable the regen paddles. Again, though, starting the ICE would have the exact opposite effect--you now have an ICE hooked to a generator adding more energy, which you don't want. It should, if anything, refuse to start the ICE for the safety of the battery pack in that situation.

In a Clarity at highway speeds the ICE can be linked mechanically to the wheels, but even then all it's doing is reducing the draw on the battery. It could theoretically do engine braking with the ICE and the transmission, but it's a heck of a lot easier to just use the calipers.

Going downhill with a full charge is exactly the situation that several of us have described for when the ICE comes on for no other apparent reason. You do ask the question that's in my mind as well: why can't the system use the friction brakes instead of rigging up the ICE for engine braking? One guess on my part is due to safety and liability reasons. You can have the situation where someone lives at the top of a long hill (some Prius owners in Colorado esp. describe this as a common scenario). If the car only uses the friction brakes to burn off the excess energy, it's possible that the brakes could overheat and thus create a safety hazard. The car (and the engineers designing the systems) cannot know how long the hill is, they can only try to design for these potential "worst case scenarios", and the potential safety issue probably trumps the inconvenience of powering up the ICE and burning some gas for most other situations.

 

[insightman]

I'm trying to imagine how the Clarity can use the engine to "burn off excess energy." Could there be an energy-wasting mode where the motor/generator reverses it's torque and uses battery power to resist the torque from the engine it just started? There is no way I can see how the traction motor can use up electricity during deceleration, when it normally functions as a generator. Isn't the traction motor simply electrically disconnected when decelerating with a fully charged battery? I guess not if the car needs to do something to compensate for the excess energy being generated during deceleration when the battery is fully charged.

 

[bobcubsfan]

Maybe this is completely different, but our Nissan Leaf would go into regen mode as soon as the car was "coasting" or if brakes were applied even with a full charge.