SoC thoughts relevant to excessive high revs/power loss.

Discussion in 'Clarity' started by Clarity_Newbie, Feb 1, 2019.

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  1. Clarity_Newbie

    Clarity_Newbie Active Member

    For the purposes of this thread, I am going with the commonly held belief Honda has built in a 20% buffer on the bottom end and a 5% buffer on the top end based on HV max cell voltage (MXV) data offered through SGll. Debatable..sure. Mo’ data needed...sure.

    My goal remains to help find answers for the excessive high rev/power loss folks.

    Using SGll data, Kiwi4 data and thoughts on the State of Charge (SoC) issue are based on observations over a two month period...and offered up for discussion. It is based primarily on the performance of the Clarity I drive but also includes the data I have off another Clarity a friend drives...her data used primarily as a qualifier against my data.

    The SoC gauge on the instrumentation panel has 20 bars. I theorize each bar has a value of 5. 15 bars are displayed...that equates to a ~75% SoC. 8 bars displayed equals ~40%. During my observations, I compared to Hondalink SoC numbers. Amazingly, the numbers correspond very well to this measure. If Hondalink is showing 27% SoC...6 bars are displayed. At ~25% SoC shown on Hondalink...5 bars are displayed. SGll reflects similar it should since the source of the data is the same…(ie) instrumentation data.

    Nothing new or surprising I guess but supplied for context.

    When EV range goes to 0 there typically remains 2 bars on the SoC dash gauge. Correspondingly, Hondalink is displaying ~ 10% and SGll is showing ~10%

    It is possible these last two bars represent the remaining ~10% SoC which translates to usable programmed into the Clarity. Emergency back-up electrons?

    I have allowed the Clarity to go to SoC ~10% multiple times for testing and have noticed the Clarity seems to throw as much energy back into the traction battery to maintain SoC at ~10% as it possibly can. To my naked seems to throw energy back to the battery more often when at two bars than 4 bars. Can't quantify...but working on it.

    If the above theory is correct...that may translate to the Clarity as engineered to maintain SoC at ~10% at almost any cost in order to operate as designed or as “normal”. If this is proven true...then those two remaining bars have a meaning.

    Perhaps this translates to 4500 to 5500 RPM’s for whatever reason on some vehicles or “angry bees” as the noise is called.

    If it is engineered that way...that begs the question:

    To the Clarity owners who suffer from unexplained, excessive high revs...two bars, four bars is needed to assess at what RPM's this occurred and whether SoC as represented on the dash gauge is ~10% or less. Example...If 2 bars...what does Hondalink show as SoC? OBDll? Possible display error if SoC actually less the 5%?

    In my case...SGll SoC data has never dropped below 8.64% and 2 bars always remained. Hondalink never breached 8%. These minimum numbers stayed true regardless of speed/terrain etc.

    As for power explanation may be the SoC is 0 or certainly less than 5 in order for this to occur. It is entirely possible the SoC is significantly lower than 10% which causes absolute max energy to flow to the battery as the Clarity is programmed to do...hence mph reduction...rather then supply power to drive a 4000lb vehicle

    One unknown for me is if the SoC via dash gauge reflects 1 or 0 bars during these events.

    If in fact the dash gauge reflects 2 bars...then can't rule out display error...or software/hardware translation issues at this point. Computer/hardware malfunction(s) are just as possible and “providing” the Clarity with erroneous data even if the SoC is ~10. The Clarity may "think" it needs to send max power to battery when in fact it doesn't.

    Until more folks can provide data...I think it is a coin flip whether this unusual high revs/power loss is battery health related or a software/hardware issue. If it turns out to be proven it is not the SoC/battery health...that won’t bode well for many others if it is a software/hardware thing.

    Mo’ data needed to help figure it out.

    Food for thought.
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  3. petteyg359

    petteyg359 Well-Known Member

    When I drove mine home right after I got it, it was the typical empty battery and full gas tank (and the ever-so-proud salesperson telling you they made very sure the gas tank was full). It did drop to 1 bar on the display during that initial drive home, but I didn't think to look at the phone to see what percent it showed. The acceleration was pretty horrid; moving away from stop lights and just trying to get 0-30 without pissing off the person behind me was obviously taxing it.
  4. MNSteve

    MNSteve Well-Known Member

    Interesting comment because I had exactly the same experience, except that I think my battery charge display was showing zero bars. I was new enough to the car at that point not to realize that this was extremely unusual, and I have not seen it drop below two bars since. I don't know what the dealer did to get it down to zero, but somehow in their infinite incompetence they managed to do so. I also had a disappointing drive home, but again I was so new to the car that I didn't realize how disappointing it really was. I have noticed in this very cold weather that even with a full charge the car often refuses to operate in EV, and I can hear higher revs on the ICE than I would expect. But "expect" is the operative word there - when you don't expect it to be running at all then you're particularly sensitive to engine noise.

    I agree that there's a correlation between very low SOC and high engine revs, and I would add "very cold" to the low SOC cause. They operate much the same in the sense that in neither case can the system pull as much power out of the battery as it wants.
  5. Dan Albrich

    Dan Albrich Well-Known Member

    I agree with Clarity Newbie and others. At one point I was complaining in these forums that my clarity both couldn't hold SoC while in HV mode, and I still always get high-RPM sound when EV range goes to zero. A lightbulb went off in my head when KentuckyKen said that not only had he never had the high-RPM sound, but he'd also hit 0 EV range.

    i.e. to agree with what's been said, my mental model is that Honda did intend for the car to be able to drive as a normal hybrid (without any excessive noise or concern) even when EV went to 0 (i.e. the hidden 10% or whatever and designed to preserve) and go into equilibrium -- so while maybe not as comfortable as an EV only ride, very pleasant normal HV experience at worst.

    A few of us (including my Clarity) seem to be unable to drive pleasantly once EV hits zero. Could be a software glitch, could be less good traction battery, ..., don't know. I suspect its the big battery. And I hate to say it but I suspect that some Clarity owners maybe when they hit 5 years of ownership will see what I see today. i.e. difficult to keep EV charge, gotta be vigilant about hitting HV anytime one may exceed EV range, and having actual range that is generally lower than predicted.

    Anyway, at some point I'll do the OBDII thing and share my numbers. Also, since my cars reboot, it's been easier to drive it normally. I'm sort of basking in the glow of normal driving, and have become almost superstitious about angry bees. i.e. I half wonder that if I allow them to come out as much as they have in the past I'll go back to the poorer driving conditions I had. i.e. Sort of afraid to push it now that I've become better at managing it (and the car since reboot has been easier to manage).

  6. Groves Cooke

    Groves Cooke Active Member

    I have experienced the high revs and seeming power loss once. Battery was fully charged and I had just descended a long hill. The noise was disconcerting and instinctively I backed off the accelerator. Hence the seeming loss of power. If it ever happens again I hope I remember to do the opposite and hold the accelerator down or even press harder and see if I still have power. The situation I described above only lasted a few seconds and may not be what others have experienced.
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  8. LegoZ

    LegoZ Active Member

    I think we will see software patches to address decrease in pack capacity. I bet there are hard coded values right now for all this stuff. I think Honda underestimates, again, the incompetence of the dealers when it comes to maintaining the fleet of vehicles that sit on their lots.
    Last edited: Feb 2, 2019
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  9. Clarity_Newbie

    Clarity_Newbie Active Member

    I have had several pm's requesting I bulletize my points from the OP. I will in the next post.

    Below are 2 pics from yesterday after a routine drive using EV nothing special or planned. I checked the SoC gauge on the dash against the Hondalink SoC. The Clarity once again displays a tight correlation to the 5% per bar at the lower range. It appears the 5% per bar is more loosely correlated at the top of the scale.

    Again...more info off one Clarity. Pic/screenshot taken 10 seconds apart. IMG_20190202_144217.jpg Screenshot_20190202-144133.png
  10. ab13

    ab13 Active Member

    An interesting responsible be what HV charge mode looks like when driving. Seems almost like the issue are going into an HV charge type of condition.
  11. Clarity_Newbie

    Clarity_Newbie Active Member

    Bulletize info from OP as requested

    • EV 0 = SoC ~10% remaining

    • 2 remaining bars on SoC gauge on dash = SoC ~10%

    • Theory: At ~10% SoC remaining...the Clarity is designed/programmed to throw as much energy as it possibly can to the traction battery in order to maintain SoC ~10% (or as close as it can) so the Clarity can continue to drive as designed (aka as "normal" whatever that is). This would explain reports of various degrees of high revs on the Clarity...high revs happen by design to provide enough power to simultaneously operate the power train and main battery SoC ~10%.

    • Theory: For those who are experiencing high revs with power is plausible the SoC goes below say, 5%, thus the Clarity is programmed to enter low power mode (aka "limp mode" to some) in order to maximize power to the traction battery to build the SoC to ~10% or maintain at whatever level it is at to minimize potential damage to components.

      Caveat...Perhaps actual SoC remains ~10% but erroneous response from Clarity due to software/hardware issues = Glitch...which a reboot may/may not help. Unknown.

    • If the above is true...that means an absolute bottom buffer reserve is ~10% with the the next ~10% being the reserve SoC that should rarely be used...if ever...and controlled 100% by computer.

    • This still allows for the defacto 20% bottom buffer to be maintained while allowing for an emergency reserve of available electrons if a problem arises as detected by the Clarity software/hardware. This 10% SoC is not available for normal driving.

    Still to many unknowns to draw absolutes. I know folks will disagree about the 2 bars and the 10% SoC emergency electrons. That is what debates are about. My data indicates this a plausible scenario. Data collection continues.

    Last edited: Feb 3, 2019
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  13. Clarity_Newbie

    Clarity_Newbie Active Member


    Good point...HV charge mode may be involved some how. That is a variable I don't plan to introduce yet but might in the future.

    Like I keep telling' data.
  14. Dan Albrich

    Dan Albrich Well-Known Member

    One heartening thing for me (as I believe my car likely dips below 10%) and hence the sounds, is that my car can increase EV with long-press EV. In other words, even in a scenario where my car (perhaps abnormally) drops EV range in HV mode, I do have a way to regain EV even when there's no EVSE in sight.

    So yes, to a point I have to manage my car more than some would like. I make a point to flat out avoid 0 EV range, and in fact if it gets to say 6 miles of EV range, time for the long-press HV, and let it rebuild.

    My daily commute is unaffected. Even on a "bad" winter day I always get at least 26 miles of EV range, and my commute is fewer than 26 miles. So I go home, plugin and the car is ready for another day of EV-only driving. I only have to actively manage things when I go on a longer trip.

  15. Mark W

    Mark W Active Member

    I have a question. Is it written anywhere that the car should not drop EV range when in HV mode? I don't think that is necessarily abnormal. To me, HV mode is made to drive like a Hybrid vehicle. When you are driving a hybrid, the state of the battery charge will vary depending on driving conditions. I have seen at times when driving in HV mode that my EV miles may go down by about 5 miles during a drive, but usually it remains fairly steady.
  16. insightman

    insightman Well-Known Member Subscriber

    It is written:

    Owners Manual, page 16
    To enable HV, press the HV button. In HV, the engine may run at
    times to drive the generator so that battery charge levels can be


    I added the red underline and ellipse to emphasize what is written. Clearly, Honda could run the engine as much as needed to implement the charge-maintaining HV Mode described on page 16, but most drivers (me included) see the SoC decline when driving with HV Mode engaged. Why, Honda, why?

    I apologize for continuing to use the term "HV Mode" when the manuals say only "HV." HV and HV CHARGE are definitely modes, but the manuals reserve "mode" for ECON Mode, NORMAL Mode, and SPORT Mode.
    Last edited: Feb 4, 2019
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  17. KentuckyKen

    KentuckyKen Well-Known Member

    Ditto on @insightman’s evidence and comments. I’ll add that on one 500 mile round trip, I only lost 1 or 2 bars on each leg and at a fill up I forgot to press HV for a few miles. So mine pretty much holds SOC during HV driving at 55 to 70 mph with some steep inclines.
    You have to remember that factors like elevation changes, wind, traffic, etc. may have a significant impact on EV range. And that the EV range reported on the dash is just an estimate based on past driving. So to truly know how much SOC you may or may not be losing, you have to measure it on the same route going both ways under as similar conditions as possible and then average the results.
    SOC is a more accurate measure of how the Clarity is holding battery power during HV than estimated EV range. I wish Honda had included the SOC% next to the battery bars.
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  18. ukon

    ukon Member

    I believe Honda's issue is charge maintaining mode; there are instances where charge can increase substantially as against capacity. So they indeed need to establish buffer. For all the math, somehow they missed some situations where the charge is maintained and lost in some cases.

    I have driven clarity on rolling hills along pacific coast. The EV miles keep changing in HV mode but keep losing 1-2 miles every 50-75 miles. This sounds like miscalculated expectations on regen by Honda engineers.
  19. smith ho

    smith ho New Member

    I am looking to buy PHEV and the Clarity is on the top of my list. But holding off because of High revs / Power loss issue for security concern.
  20. KentuckyKen

    KentuckyKen Well-Known Member

    My best advice (and I freely admit I’m a Clarity fan boy after 1 yr and 7k miles trouble free) is to test drive one that has been charged up. Then drive about 30 to 50 miles depending on the temperature until it hits 2 battery bars and zero EV range. This will force it into HV with its minimum battery charge. If you don’t get the power loss thing then I would think that particular car’s OK. The vast majority of us are not having this problem and an even greater majority on this forum love their Claritys. My Clarity is the best car I’ve ever bought.

    I will say that most dealers are clueless and have little to no experience with servicing the Clarity so in that respect you will end up being an early adopter, if not beta tester, like the rest of us.
    Depending on your aversion to risk, you can lease for 3 years or buy and purchase a Honda Care 8 yr/100,000m warranty for $1,304.
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  21. Dan Albrich

    Dan Albrich Well-Known Member

    I have one of the less awesome Clarity's and still love it.
    5-days a week, for me my commute is fewer than 26 miles, so I'm all electric. Very quiet smooth and low-cost ride.
    Occasionally, I go on a long trip and have to be somewhat mindful to avoid 0 EV range. In my case (not all) I hear a high RPM sound if EV hits zero. To be clear, the car still has power and runs fine in my case, but I don't care for the sound. It sounds like someone driving in first gear beyond when they should shift.

    I admit, I've *never* experienced a significant power-loss. I mean when EV goes to zero, I hear the sound, and it's not quite as peppy but certainly no safety issue. i.e. I can still accelerate onto a freeway ramp or whatever I need to do.

    Also if you testdrive in the winter, and get something close to the rated 47 miles of EV range, that would seem to me to be a good traction battery. My Clarity with 32 degree nights and 50 by day doesn't generally see more than 32 EV miles of estimated range. I think folks who see 40's, high 40's or greater literally have a better battery than I do.

    But yes, if temps similar or colder, and you test-drive a clarity with say 40 or more miles of EV range this time of year, I'd say that's great.


    PS: In good weather my Clarity does see 47 estimated EV range (i.e. summer).

    Oh and one more thing: Ask the dealer to charge the car before you test-drive. You can't see the EV range I speak of unless the car has been plugged in.
    Last edited: Feb 4, 2019
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  22. smith ho

    smith ho New Member

    Thank you for your advice.
  23. The Gadgeteer

    The Gadgeteer Active Member

    When I test drove my Touring Clarity I didn’t know what I know now but I did notice it had no charge, zero bars. It was a windy cold 5F out so between the lack of charge, the heater on full, and the extreme cold the engine stayed on and at times the revs/sound didn’t reflect the slow residential speeds. In fact it got very loud and highs revs when I tried HV Charge. So I took it out of HV Charge. Anyway it still drove horribly but I knew that must be because of the drained battery. The base Clarity I test drove at a different dealership the week before was charged and drove beautifully. I did get the Touring with the drained battery but made the salesperson promise to charge it before I picked it up.
    Even though I have not had any issue since but I keep the battery charged. I cannot help but wonder if my Clarity battery was damaged or life shortened by a dealer that let it fall below 2 bars charge. I will have to test it at 0 miles EV range and see how it behaves.
    Last edited: Apr 14, 2019

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