Just got my Clarity Plug-In a couple days ago and I have an efficiency question

Ken,

While I would agree with you that this is the general consensus, I disagree with that concept.

In any hybrid vehicle, there is a battery for storage of the energy recovered from slowing and braking. For instance, a Prius has a 0.9 kW battery. Without a battery, there would be no hybrid vehicles at all.

For the Clarity, those 2 bars that remain when the car changes to HV mode on its own are the "hybrid mode battery", for lack of a better term. The state of charge on the battery fluctuates when in HV mode based upon the state of charge and the power requirements. I have seen on many occasions when the state of charge has gotten down to 2 bars that the car will go into EV mode even though the EV range is zero. The blue bar will appear on the power meter but only extend up to the second large mark at about the 10 o'clock position. If I keep the power request within that blue bar, the car remains in EV mode. You can't accelerate quickly, but I have driven for over one mile with zero showing on the EV range and the blue bar slowly shrinking from 2 tick marks down to 1.

This is just how the battery works in a pure hybrid. No reason to think that the Clarity is any different when in hybrid mode.

Just my opinion.

 

Hark, yet another Clarity mode mystery (and my theory about what is going on): Iconless HV Mode.

You're cruising along with HV Mode disabled, proceeding under EV power. The EV icon is on and the ICE is off. Then the Clarity's EV range goes to zero and the battery gauge shows two bars. Refusing to delve into the forbidden two-bar zone, the Clarity starts its ICE in what I'm calling iconless HV Mode because the Clarity acts as if it was in HV Mode, but the HV icon does not appear.

As in the non-EV phase of HV Mode operation, the ICE starts and turns the starter motor/generator to both power the traction motor and recharge the battery. In this iconless HV Mode, as soon as the ICE has added a small charge to the battery--too small a charge to display a third bar--the Clarity switches back to EV drive mode. When the small charge is depleted, the ICE comes back on and this cycle continues until you select HV CHARGE Mode, find a steep hill to descend for some healthy regen braking, or plug in. That's how I've interpreted my experience--your experience may vary.

 

I don't really consider this a mystery. It might be a UI bug (or more likely just unclear design) in terms of what icons it shows, but all of my experience driving with an empty battery the behavior is as you described, which makes sense.

2 bars is "empty" as far as the car turning on the ICE goes. The deadband its battery management routine maintains is relatively narrow, such that if you regen a bit, or the ICE runs for a bit while at low speeds, you end up with a little excess energy in the battery, which will be used either when accelerating, or, if you baby it, to cruise at low speeds for a short distance. This is actually extremely similar to how a Prius or other mild hybrid works, you just don't see the battery state of charge in those vehicles so it's invisible.

It's possible your car is behaving differently from what I've observed, but assuming the behavior is similar you could think of it like this: The ICE has a minimum speed it can run, and therefore a minimum amount of power it can generate regardless of what the wheels are using. Additionally, it probably runs most efficiently, in terms of generating electricity, at some level above idle. Third, if it starts up and is cold, it will run for a minimum period of time to get up to temperature before it will turn off; I'm assuming though have not observed that there's some additional hysteresis such that if it turns on once warm it will stay on for at least some number of seconds minimum.

The car, therefore, presumably aims to run the ICE at an efficient point as necessary and possible. At highway speeds on a flat or mild-to-moderate uphill, this basically results in it linked to the wheels and running at a roughly constant speed. At slow or stop-and-go driving, this may result in the ICE running for a little bit, adding a few % charge to the battery along with regen braking, which then results in the ICE not necessarily turning on right away when you start moving again.

This all makes sense, works, and probably operates as designed, and becomes visible to the user through the blue area of the energy gauge moving around. But because you can't see precisely what the car is doing or why it's making its decisions, it appears somewhat random. The algorithm maybe seems clearer to me because I'm a power control systems programmer by trade, so I kind of have an intuitive sense of what it's doing behind the scenes.

I think a lot of what people perceive as "mysterious" is really a combination of unclear UI design (calling it "HV Charge" vs "Mountain Mode", having the white area on the power gauge indicate ICE start up in some modes but not others), providing a mix of too much and too little information to the driver, and people trying to overthink or second guess fairly complex energy management software routines that--if you ignore them--"just work". If the UI provided no information, you wouldn't notice--like a regular ICE or most mild hybrid vehicles. You'd just drive and notice the ICE did things. If it provided way more info, you'd know what was going on, but drivers who didn't care (my wife, say) would be confused and intimidated by it. Honda picked somewhere in between, which is enough to make me happy (though I really wish there were units of kW on the power gauge) but apparently is confusing for some drivers.

If we're talking about pure economics what you say is true--if you have really expensive electricity and really cheap gas, it might indeed be cheaper to run all-gas all the time. You should keep in mind that oil changes and engine service aren't free, so gas miles have additional costs past just the price of fuel. (As, technically, does EV if you factor in battery pack degradation, but then you'd need to factor in ICE wear as well.)

But for myself, at least, the ecological and noise benefits of running all EV outweigh the price advantage even if gas is cheaper, and it seems likely to me that is going to be the case for some fraction of people who have spent the money for a Clarity. If price were the only thing you cared about and gas were that cheap where you live, why the heck wouldn't you just buy a cheaper non-plug-in mild hybrid?

For me of course that's not the case anyway. Gasoline is well over $4/gallon and power at home during off-peak is under 10 cents/kWh, so EV would be way cheaper even if I didn't have solar (which I do, so as you mentioned the incremental cost of electric fuel for driving is literally zero).

 

Yes, I used the word "mysterious" because it's one of those situations where the Clarity's user interface isn't doing a good job to keep the driver informed. I wish Honda would let me pay hundreds of dollars for an optional total-information screen.

 

I think there's one more factor that triggers the ICE - temperature and/or need for heat in the cabin. This factor has been reported in a few other posts here, and today I experienced it for the first time. When I started the car this morning the ICE came on immediately. I had just disconnected the charger so the battery was fully charged, and I wasn't braking since I wasn't moving. But it was very cold; the car's temperature was about 10°F and the outdoor temperature was 0. I drove to my first stop about two miles away and the ICE ran during that period. When I came out of the store and restarted the car, the ICE came back on. Several minutes later it turned off and put me back into EV mode.

Then something happened that I've never before observed. I was sitting stopped at a traffic light and the ICE restarted. The display showed energy flowing from the engine icon to the battery icon. When the light changed and I started moving, after a minute or so the ICE turned off.

When I came back to the car from the second store, the car started up in EV, but about a minute later the ICE started. It ran for a couple of minutes then cycled on and off as I returned home. It turned off as I turned into the driveway and did not restart before I turned things off.

A possible explanation for this is the car deciding that it needs the waste heat from the ICE to heat the cabin rather than sucking energy from the battery. It could be restarting the ICE when the coolant temperature drops below some threshold. But as usual this is all speculation; maybe it was the relative humidity.

 

Me, too.

But I think the user interface is doing a fine job of keeping the AVERAGE driver informed. As others have said, they're trying not to overwhelm folks with too much information or too many options. But they're trying to hit the peak of the normal curve; some folks will still find the car overwhelming, and some folks like us will want every tiny detail.

 

Its not just about pure economics, if I use HV I get to run cabin heat too and be warm!

 

One of us (me) can't retain EV charge when in HV mode even on flat ground. It doesn't tick down quickly but it does on my car and it does not self-recover. This affect gets worse if the terrain is hilly. On the hills I lose even more EV range that doesn't self-recover.

So on my fairly routine 200 mile trip on flat ground, even with HV mode on from beginning, my EV hits zero unless I long press HV which does recharge the EV.
My mileage has been good (~40MPG) even with using long press HV to recover enough EV range to keep the car in 'normal' HV mode.

Anyway, if I do nothing and let things ride at 0 miles EV range, I get the high RPM sound (and it sticks on high and doesn't stop until I turn off the car or acquire more EV range by plugging in, or long-press HV). So my uses of long press HV is common. I don't think its a big deal. I do it mostly to keep the car sounding and feeling normal. i.e. driving with 0 miles EV range in my car also makes it a bit gutless. Not dangerous to drive, just less responsive.

So anyway, YMMV, but my whole goal is to always avoid 0 miles EV range. And, long press HV in my case is sometimes required to do that (based on trip-length).

 

So much variation in the way these cars operate is really strange. Certainly you should go to a dealer and see if they find anything wrong, although it seems unlikely they will. Certainly seems there must be a sensor malfunctioning or something.

 

Dan - Is this loss of EV range in HV mode all in one stint, or does it go down over the course of several trips? I ask because when I switch to HV mode it may lose 0 - 2 miles of EV range during normal driving. If I stop and shut down and come back and start-up and go in HV again, the EV range set point may be 1-2 miles less than it was when I started the previous stint. And over the course of a day in HV mode with several on/off cycles in between (yesterday for example), I can drop about 25-30% of battery (~10 miles of range).

Just wondering if that could mirror your observations, or are you seeing full EV depletion in HV mode without any on/off cycles in between.

 

Hi Ray, and thanks for you note. You ask:
"Dan - Is this loss of EV range in HV mode all in one stint, or does it go down over the course of several trips?"

The answer is both. What I mean is if I do a single 200 mile journey without stopping my EV range still goes from whatever I started at to zero. The progress downward in HV mode is slow, but predictable. So for example, if I start with 28 miles of EV range, say hit HV on the highway at 25 miles of EV range, I can get close to 100 miles before hitting zero EV range. And I mean without stopping. These are freeway miles at about 60-70Mph. I work around this by long-press HV, just to get the EV range above zero, maybe get 10 miles of EV range, then go back to HV mode.

Secondly, I also notice the effect you mention. Lots of short trips definitely makes this worse. The car will lose 2-3 miles temporarily and under certain conditions will regain a mile or 2 in HV mode, but if one stops right after losing 3 miles of range, that definitely stays "lost."

Also I do understand not all Clarity users see what I see. In my first example, I think many clarities would retain EV range on flat ground, even on freeway in HV mode-- just not mine.

My dealer is hard to work with. I've determined to mention this issue if I take the car in for anything including A01 maintenance, and mention I want the battery test done. I'm a little skeptical they'll do it. They told my friend who bought Clarity from same dealer that no such test exists, and everything that can be known about battery state is on the display. Obviously this is incorrect/untrue, but every interaction with these folks is a battle, and one must weigh the value of your precious life moments too. i.e. I presume even if I "go to the mat" for this, I may still not get a good outcome, at least not from my local dealer (which is only Honda dealer in the cities where I live - Eugene/Springfield).

-Dan

 

That's what I see, too. Certainly, Honda could have programmed the Clarity to maintain the battery charge at the level when you pressed the HV button: You press the HV button, the computer records the level of battery charge, the charge dips below that number, the computer raises the speed of the ICE to return the charge to the original level without affecting the Clarity's road speed.

The only justification I can imagine for allowing the battery charge to decay during HV Mode travel is to prop up the Clarity's EPA fuel economy rating. I don't believe HV Mode battery-charge decay is an indication of a problem that a dealer can address--it's the way the Clarity was designed.

 

HV mode is what their technical papers refer to as "Charge Sustain" (CS) mode, and they tend to show it being effective at holding the prescribed level of charge when it is activated. But I wonder if the CS system is only tracking use of the battery to run the car motor and engine as the only outputs and neglecting the use of the traction battery for the heater.

So I wonder if this "HV mode SoC decay" is a seasonal thing and less pronounced in moderate climates. I didn't use the HV mode very often in the fall, but I didn't notice a loss of EV range / SoC, but now it does seem to drop a little more consistently this season when I am using the cabin heat.

 

Another seasonal impact that could contribute to HV mode SoC decay is that regen seems to be a lot more variable in winter weather. Some times the regen chevrons blink and drop 1 or 2 of them while decelerating and even when it does operate at times the amount of recharge on the dial display is a fraction at what is observed on warmer days. Perhaps this plays a role as well.

Obviously the computer should only pay attention to SoC and run the engine to keep up and sustain the SoC and ignore these inputs and outputs, but just tossing it out there as another potential factor.

 

Dan, your car is definitely behaving differently from mine, and I think not as designed. While in HV mode on either highway or around town, mine will always retain charge. On interstate cruising through the mountains, the charge will go up and down a little, but seems to average at the 67% or higher mark. If I have more than 67% charge, it will very slowly lower to 67% on a long highway trip (usually, but not always). If I go into HV with less than 67%, it stays at that level (i.e. go into HV at 30%, charge stays at 30% forever). The only time it drops to 2 bars is when I (or family member) forgets to press HV after a pit stop.

I really wish Honda engineers had made a configuration setting that would keep car in HV while on a long trip. After a pit stop, the screen could flash up a message like "Extended highway travel detected, retaining HV mode, press "I" to disable".

 

Great idea. Meanwhile, I have a paper solution. I made this "HV" button and taped it over our Clarity's "D" button for our first long trip. It reminded me to press the HV button before proceeding further.

 

Or maybe the blood red wolf moon

 

Dan, my Clarity too will sustain the SoC on Long HV trips. I’ve only done them in the summer, but heavy AC use did not keep it from sustaining the charge.
I’m sorry yours isn’t and I’d be bummed out if mine was doing that. Maybe and hopefully it will be something that can be diagnosed like a faulty sensor or something.

Have you tried resetting the car by detaching the 12v battery cables and making it kind of start over? It’s a long shot but who knows?

 

I have a question now, and please understand I love all the help I received from these forums so just fishing for some good advice.
I unplugged the negative lead on my battery and let it sit about 30 seconds then re-connected. The car is in the process of rebooting? or has been since last night. I went to bed thinking messages would clear but have not.

I get system initializing... drive carefully. CMBS failed, TPMS reset required, and some others that flash by.
I know where the TPMS caliberation is so I went there. Each attempt at re-caliberate says 'failed to start'

The car when I turn it on, seems stuck at system initializing. Is this normal for pulling the 12v, or do I need do something else?

Hints/help at clearing alarms are appreciated.

-Dan

 

Sorry for the immediate followup to my own question. I decided to just drive the car around my own neighborhood. I figure if I have a more major problem just want to be close to home. All of the warnings seem to have cleared just driving it around. No clue what all this means but happy to have the car back in a normal state. Also when the warnings were showing I could not select modes like econ or sport. Just an observation.

-Dan