Clarity 2021 engine over-rev and battery below “2 bars”

[F.Roy]

Hi all,

I have had the unpleasant experience twice now of having to stop by the side of the road due to the gasoline engine over-revving to the point where the car was unable to maintain hwy speed. Here were the conditions prior to the over-revving happening:

-Driving on highway at 55-60 mph (90-100 km/h) in hilly terrain (from 500ft to 2000 ft approximately)
-only 2 people on board. Light luggage
-outside temperature of 50-60 F (12-15 deg C)
-EV and ECO mode were selected
-EV range eventually decreased to 0 which has always coincided with indication of battery charge down to “2 bars”.

The issue started when for whatever reason the charge level of the battery was allowed to drop to “1 bar” only. This was followed by an increase of gasoline engine RPM to a level unknown since there is no RPM gage, however with 45 years of driving experience on standard transmission It felt like I had downshifted to 3 gear; I had to let go of the accelerator and was unable to maintain my speed; the over-rev was just too much.

There were no indication/lights/warning at all. I stopped, switched to HV mode, waited for the battery to charge up to “2 bars” again and went on my way without further issues.
However, This exact same scenario happenend again in the same stretch of Hwy about 2 months later. I took the car to the dealer that time. No codes were on. Car appeared normal on all aspects to the mechanic. He was supposed to call Honda Canada, investigate and call me back since this dealer sold very few Clarity and he admitted they did not know the car very well: It’s been a month and I haven’t heard back.
Anybody else experienced this over-revving after the battery charge was allowed to drop to “1 bar”?
Thanks in advance.
François Roy

 

[MrFixit]

@F.Roy

There is nothing wrong with your car. This behavior is 'normal' when the HV battery is depleted and the vehicle is stressed (particularly with sustained uphill grades). If you search this forum for "Angry Bees" you will find a LOT of information / discussion about this.

On the positive side, you can avoid the "Angry Bees" almost entirely by being knowledgeable about your driving scenarios and making sure that you don't operate in stressing scenarios with a depleted HV battery. When I go on a long trip (longer than the EV range), I always switch to HV mode with around 50% remaining on the HV battery. If, during the long trip, the HV battery level drops, I will use HV charge to boost it back up again. once I reach a point where I can make it back home (or to a planned charger) on the remaining EV miles, then I switch back to EV and use the rest of the battery charge while completing the trip.

We rarely hear about complaints with the "Angry Bees" any more because most have learned how to avoid them (and it's really not hard to do so).

 

[JFon101231]

You indicated it was "unable to maintain highway speed" but it sounds like you let off the accelerator from the wording.
So at a reasonable accelerator angle could the car not keep up highway speeds, or did you let off (due to the sound perceivably being an overrev situation in your view)?

Depending on your answer, and admitting its never happened to me (or at least a sound so loud/high revving I deemed it concerning/bad for the car), I think frankly it is within the operating specs of the car as designed hence why no lights or flags for tech. If i know I'll deplete Ev range on any given longer distance trip I try to go to HV once I'm around 60% SOC and then go back to EV at my estimate of mileage remaining to end at zero to avoid this.

 

[pigrew]

If everything is working as designed, it did not over-rev... in fact, I doubt that the engine can over-rev since there's only a single gear ratio between the engine and the wheels (or maybe you'd have to be going excessively fast, like 100+ mph).

The engine is more efficient at high-revs, so that's where it naturally will set itself to. When it's doing that, it's using the excess power to charge the battery (to prepare for the next hill you'll be driving up).

 

[Landshark]

If everything is working as designed, it did not over-rev... in fact, I doubt that the engine can over-rev since there's only a single gear ratio between the engine and the wheels (or maybe you'd have to be going excessively fast, like 100+ mph).

In the described scenario from the OP, the engine was at least 99.99% likely to be running as a generator, with no direct connection to a transmission and the wheels. It was making electricity which was driving the electric motor to the tune of about 60hp. As stated the engine is unlikely to “over-rev”.

Best bet when in that pickle is to put the car in HV Charge until the SOC gets up to 50% or so and then keep it in HV until there’s 10-15 miles to go on the trip.

 

[StickWare]

I would try to Goto HV at three bars to prevent this.


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[Dan Albrich]

I do wish Honda would of made the HV button sticky, instead of the "econ mode" button which is sticky. My wife and I usually drive fewer than 35 miles a day (all electric). When on any trip that exceeds EV range, we just get in and press HV right away. We doggedly protect the electric charge. If by chance or conditions we drop to where EV estimated range hits or goes below 10 miles, we press and hold HV (to get HV charge mode) which gets it back up to a little above 1/2 estimated EV range.

Anyway, once you know this and stay dedicated to it, the car works perfect all the time. I normally don't lend cars, but sometimes do with family. If they need my car, I literally put a sticky note on the "D" button that says "HV?" -- the meaning is to remind them to just hit HV first 100% of the time. There's no need to maximize efficiency in such situations and its way simpler. And like I say, I wish Honda would of permitted the HV setting to be sticky for ease of use. But such at is it is, you just hit it any time you *might* exceed EV range, and all is well.

I only ever have "problems" with my Clarity if I let the EV range go to zero, so I just never allow that.

-Dan

PS: In my case the only "problem" I've had is the high rev sound (angry bees). I don't like it, so I don't ever let it occur. The sticky note idea came from another member of these forums. The sticky note works well.

 

[PHEV Newbie]

Even in hybrid mode, the car is constantly recharging the battery and discharging the traction battery to maximize mpg. Lithium ion batteries always do best (charging, discharging, and storage) near 50%. Thus, I always switch to HV mode on longer trips when the battery is near 60%. That also leaves me with a significant reserve for extended uphill driving and for EV mode in stop and go traffic. The BMS seems to be programmed with that in mind. Early on, I wanted to keep a big reserve (about 90%) on a road trip. The battery would not hold at that level and drifted down to stabilize at about 70% where it stayed for many hundreds of miles. That could be just my car but it always does that. That is also likely the reason charge mode tops out at 58%. Engine charging is pretty quick so the BMS likely is doing that to protect the battery.

 

[insightman]

Even in hybrid mode, the car is constantly recharging the battery and discharging the traction battery to maximize mpg. Lithium ion batteries always do best (charging, discharging, and storage) near 50%. Thus, I always switch to HV mode on longer trips when the battery is near 60%. That also leaves me with a significant reserve for extended uphill driving and for EV mode in stop and go traffic. The BMS seems to be programmed with that in mind. Early on, I wanted to keep a big reserve (about 90%) on a road trip. The battery would not hold at that level and drifted down to stabilize at about 70% where it stayed for many hundreds of miles. That could be just my car but it always does that. That is also likely the reason charge mode tops out at 58%. Engine charging is pretty quick so the BMS likely is doing that to protect the battery.

That HV Charge limit is the only hint that Honda's engineers didn't want drivers always trying to keep their batteries fully charged.

I don't know why the Claritys of some forum members rigorously maintain the HV set-point while other forum members report their HV charge level slowly drops from the initial set-point. Perhaps the latter might be preferable because forum members whose Claritys maintain the set-point are tempted to leave the car on during a bathroom break simply to avoid having to accept a lower set-point after restarting.

 

[Landshark]

That HV Charge limit is the only hint that Honda's engineers didn't want drivers always trying to keep their batteries fully charged.

I don't know why the Claritys of some forum members rigorously maintain the HV set-point while other forum members report their HV charge level slowly drops from the initial set-point. Perhaps the latter might be preferable because forum members whose Claritys maintain the set-point are tempted to leave the car on during a bathroom break simply to avoid having to accept a lower set-point after restarting.

My belt and suspenders theory on the HV Charge limit of ~60%, is that the charge rate appears to be considerably higher than the L2 charge rate of 0.4C, possibly in the neighborhood of 1C. While that isn’t an alarmingly high charge rate for lithium batteries, it may be one that the engineers didn’t want to allow above 60% SOC. Who knows?

The manual does recommend fully charging the battery prior to each trip, which is certainly different from trying to keep the batteries fully charged at all times. That would be an indication that the engineers weren’t particularly concerned about fully charging the batteries on a daily basis, for those who drive the car every day. We’ve maintained a rigorous protocol over the past 3 years of fully charging the battery after each trip, so that it is ready for the next trip, whenever that may be.

Our car happens to be one of those that only loses 2-3 bars of charge on long road trips, even with a couple of fuel stops.

 

[Dan Albrich]

In case helpful to others (and I've reported my story some years back so a bit duplicative): Got clarity new October 2018, mine manufactured June 2018. First trip with wife was to crater lake. Long drive, and mountainous, and the rim itself is a lot of up and down. Knew nothing about the car then, prior to reading this forum. Car went to 0 EV range, and did some angry bees. They have a free L2 charger at Annie Creek, so I tried that. It seemed to be charging while we went for a hike. Came back tried to start car. Got a ton of system power degraded type messages. Found out later there's a software fix for what we experienced.

After night fall it gets cold on the rim and we wanted to drive home. Car was showing tons of warnings which I ignored. I figured there's a chance we'd be stranded on the side of the road on the way home. For those that don't know this area is fairly remote and not a lot of services. Wanted to get the car down the mountain to hwy 97 and over to population in case we got stranded. There's very few services at the rim itself.

Drove all the way home (about 3 hours I think) to Eugene hearing angry bees. Turning off the car and back on again didn't dismiss the error messages. During the following next day, driving the car around the block, the errors cleared. I had made an appointment at the dealer but had to wait a couple days. By that time it was more or less normal.

Drove the next few months with constant angry bee sounds, anytime the gas engine turned on. Our commute is fully EV, so not often. Also when driving in HV mode, even if start in HV with full EV, car would lose range to EV=0 within 100 miles. Very consistent problem. Didn't know some folks press HV and the EV state is maintained-- my Clarity doesn't do that.

Kentucky Ken in these forums suggested I reboot my car by removing 12v terminal, and replacing. I did so. After some more scary warnings that self-clear my car came back to normal. i.e. just drive 10 miles or whatever small amount, and the warnings go away. Car started performing normally (no angry bee sounds) anytime EV range not equal zero. It still slowly loses EV range even when I don't stop, but over 100 miles I lose about 12 miles of EV range. When the EV range gets to about 10, I press HV charge and re-build. Been driving the car this way ever since. Interesting to note, my car does not make angry bee sound, ever, in HV charge mode. It only exhibits the extreme high-rev sound if EV=0. So HV charge is my friend, and I use it routinely on long trips. Other than that my car runs great. Day to day, my EV driving is usually fewer than 30 miles, so I don't need to drive in HV except on longer trips.

Still love the car, not complaining, but I've never seen my car sustain EV range when in HV mode. I learned in these forums that this is normal behavior, but I never see that. One wonders out loud if my ill-fated charge at crater lake caused some other problem. I don't think I'll ever know.

But the car became reasonable to drive again in HV mode after the reset.

-Dan

PS: I don't recommend "normal" clarity owners do the 12v reset. I had some problems others in this forum don't see. i.e. reason I did it. Not that it will hurt your car, but I wouldn't do it trivially either. I do believe experience from Clarity to Clarity can vary. Lots of folks handing out driving advice, but I know for sure my car doesn't maintain HV charge period, no matter how I drive. I got "over it" a long time ago.

One last detail (edit): I sort of privately (not willing to argue the point) believe that it isn't safe for anyone to run Clarity when EV=0; I say this because I am not willing to force my Clarity to EV=0 even just for data gathering sake. I simply don't care about that, and want to keep it running smoothly. Its function (even if not normal) is fine for my uses.

 

[Landshark]

Wanted to get the car down the mountain to hwy 97 and over to population in case we got stranded. There's very few services at the rim itself.

Drove all the way home (about 3 hours I think) to Eugene hearing angry bees.

Mostly unrelated, we’re headed to Springfield/Eugene on Thursday for a few days to visit friends and scout a couple of RV parks for a Rally that we’re co-hosting next June. We did most of the rim on our bikes, until we encounter a snow bank and bulldozer a few years ago.

We had our car delivered to Brookings from Eureka, with 0 EV miles. Drove it to Medford on 101/199/I-5 in HV with no issues. Then, a few days later, I proceeded to drain the battery going up Siskiyou pass in EV, drove through Trinity-Shasta, past Redding and somewhere in the San Joaquin valley I decided to try HV Charge and got the batteries up to ~50%. Did all that hilly N Cal terrain with 0 EV range. Sure, the engine buzzed a bit, however there was no loss of power, no warning lights and after years of riding high performance motorcycles with 10,000+ rpm engines, the noise didn’t bother me a bit. The only disconnect is the rpm v acceleration that we’re all familiar with. Of course, now I know better than to deplete the batteries when demanding conditions lie ahead.

 

[Dan Albrich]

Yes and thanks for the pic of the rim. I've ridden my bike on the rim on one of the days where its closed for just bikes (save to park). I think I made it about 1/4 way around as I'm not in super-good shape. My friends have done the whole thing, but the up and down is a killer. I also used a steal frame mountain bike from 30 years ago, not a modern light weight one. Not sure I would of made it even so, but I think the newer bikes are lighter. I love crater lake.
BTW- for those curious, if you get the opportunity to stay at the lodge as I did last July 4th weekend, the lodge completely lacks air conditioning. Sort of an "authentic" if not comfortable experience. Read I didn't sleep at all (too hot in the rooms). I did do some fun night photography though (basic delayed shutter stuff). My pics have some foreground over-exposed which is easy to do for beginners.

And to save this post from being completely off-topic-for ev, Landshark's point about saving EV charge for hills is spot on. The electric motor is more powerful than the gas one which can be counter-intuitive for the uninitiated. I do find it simple to plan, but I absolutely plan for the hills and mountains saving EV charge for them. If you find yourself in super-hilly country where you cannot avoid running EV to 0, one can safely, and for hundreds of miles run in EV charge mode. I do it about once a year. Now I'm sure gas mileage takes a hit doing so, but its absolutely possible even in continuous hills to keep some EV charge.

One last thing for the benefit of the thread. I am familiar with the EV range going to 66% even under ideal conditions. My Clarity continues to drift downward, and would drift all the way to zero. And no, even not including stops where the set point gets reset -- which happens to everyone. At least one Clarity (mine) absolutely loses EV range in HV mode no matter the conditions including below 40% (or any arbitrary point you name). It absolutely does not stabilize EV on its own, ever. I can (and do) press and hold HV to go into the charge mode, and must manually do so to retain EV when in HV mode. No other way to retain EV range on my car. Anyway, not arguing a point, other than to say not all Clarities behave the same-- or mine doesn't anyway. My dealer is aweful to work with, and there's no chance to describe any subtle issue to them or have them care about it.

 

[BCharge]

Something I have noticed in my 2018 touring during highway driving in HV is that I gradually lose EV range and battery bars when also in Econ mode at the same time, until EV range goes to 0 and bars drop to 2. When in HV and no Econ mode battery bars remain stable and the EV range estimate will vary within +/- 3 miles or so.

Just got home after a weekend trip through eastern PA, 5hrs round trip. Outbound, I turned on HV once I got to the freeway and EV was about 15 miles. With Econ mode off EV went as low as 13 when maintaining 70mph cruising through uphill terrain, and then EV went back to 15 when terrain leveled off. On the return trip I drove the whole way with battery on 2 bars and Econ mode off, and only got high revs for a couple minutes going up a particularly steep grade.

As a habit I only use Econ mode while driving in EV, and switch off Econ whenever in HV. I enjoy how the car responds on the open road.


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[gedwin]

As a habit I only use Econ mode while driving in EV, and switch off Econ whenever in HV. I enjoy how the car responds on the open road.

Interesting, I’ve never played much with the economy mode button. (Always leave it on.) I’m curious, do you have any sense of the mpg penalty for turning it off when on the open road? I realize that may be hard to answer, but, let’s put it this way: do you still generally get 40+ mpg on average with Econ off?



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[MrFixit]

do you still generally get 40+ mpg on average with Econ off?

I have no experience with non-Econ operation, but this is all that it says in the manual:



"Less" control over temperature with the climate system would seem to have little impact. Behavior of the seat heater would have no impact in the summer, maybe a minor impact in the winter by encouraging less use of cabin heat. The behavior of the accelerator / engine starting would have no impact when on the open road and travelling at a relatively constant speed.

My guess is that Econ mode has an imperceptible impact on fuel economy when on the open road in HV mode. Perhaps there is a minor impact around town and maybe a little more in the winter.

 

[BCharge]

Interesting, I’ve never played much with the economy mode button. (Always leave it on.) I’m curious, do you have any sense of the mpg penalty for turning it off when on the open road? I realize that may be hard to answer, but, let’s put it this way: do you still generally get 40+ mpg on average with Econ off?



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It is hard to tell what impact driving with Econ off has on overall economy based on my driving habits. I suspect I might lose a couple miles of EV range and a couple mpg in HV, but I haven't tried any head to head comparisons with different settings in similar conditions. As MrFixit says, I suspect it is quite negligible with consistent highway travel. Travel sports will be ramping up for the family again in a couple weeks, so this string tempts me to do some experimenting. I'm also about to replace the OEM tires after almost 32K, thinking about the CrossClimate 2 based on other posts on this forum, and am very curious about the impact of different tires on mileage.

 

[Roy2001]

When battery soc is low, you will completely rely on the 1.5L small engine and it struggles during freeway passing and hill area. So switch to HV mode early.

 

[Johnhaydev]

I replaced the OEM Tires with cross climate 2 tires a few weeks ago. On the original tires, I could barely make the 46 mile round trip to work from home only using the traction battery. After replacing the tires, the gas engine starts at about 4-6 miles before I get home. So you do seem to lose a significant amount of mileage based on my experience.

 

[Dan Albrich]

Cross Climate 2 seem like good tires (good traction). It's a trade off between low roll resistance (which is what the car ships with) and better traction.
So yes, range takes a hit, and they seem to be nice tires.