Honda Service Express Bulletins for 2018 Clarity PHEV

Discussion in 'Clarity' started by AnthonyW, May 31, 2018.

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  1. AnthonyW

    AnthonyW Well-Known Member

    I recently purchased a one day subscription to Honda Service Express ( and did some research on the Clarity. Not a lot of information outside of DTC explanations and fixes but more will come with time. Here are some of the more interesting bulletins I found.

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    zlscoolcody, RickH, Alx and 24 others like this.
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  3. iluvscuba

    iluvscuba Active Member

    Since I haven't been in this car for quite a few months now, may be my memory is a little fizzy. Anyway in the 'Electric Powertrain System Description' document, it said 'EV driving mode can be manually selected by the driver and is available based on current vehicle condition.' I don't remember as a driver you can select the EV mode as there is no such button to push. In ECON and Sport mode, the engine can still come on, is it not?
  4. bobcubsfan

    bobcubsfan Active Member

    Loads of modes. I would recommend downloading the manual. It is NOT organized very well, but there is SOME useful information. For example:
    There is NO EV mode as such. It would be nice if we could keep the ICE from coming on at all. I think Honda owes us all a gas card to compensate for the waste of fuel because the onboard computers are NOT programmed correctly
    hanman and glockgirl like this.
  5. Steven B

    Steven B Active Member

    The default startup is in EV mode. The third button (far right) in the magnified view above is the HV button. This takes the car out of EV and puts it into HV with a short press or into HV Charge with a long press. The EV mode qualifier "is available based on current vehicle condition" means that if vehicle's brain decides the ICE needs to run based on (1) how long it has been since it last ran, (2) based on certain environmental conditions the vehicle is in (extreme cold, heat, presence of heavy lead foot, etc), or (3) if the driver has fully charged the battery but asked for regenerative braking. In each of these conditions, the brain may decide to turn on the ICE and there is nothing short of leaving the gas tank empty that the driver can do to prevent this.
    hanman and KentuckyKen like this.
  6. bobcubsfan

    bobcubsfan Active Member

    I kiddingly asked the dealer to install a manual kill switch for the ICE. Then I could shut it off or turn it on when I feel like it. IBM = Is Better Manually.
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  8. iluvscuba

    iluvscuba Active Member

    bob, I was referring to the 3rd line of the document that said the driver can manually select EV mode. I am not sure how much I can trust Honda's service if their Service Express documentation describe something that does not exist in the production car
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  9. KentuckyKen

    KentuckyKen Well-Known Member

    Bob, I’ve kept careful records and in 2,100 miles over 3 1/2 months, my HV range has only gone down by 35 miles and I’ve only noticed the ICE turn on 4 times and each time was very brief and low key. So I’d have to say that’s not bad at all for a PHEV and seems to be programmed alright except for the occasional full charge/no regen ICE. I think StevenB nailed it in his post.
    gedwin and Jed like this.
  10. Sandroad

    Sandroad Well-Known Member

    Thanks! That's really cool. I appreciate your posting these. Some good solid information about the car!
    Jed likes this.
  11. bobcubsfan

    bobcubsfan Active Member

    Note the button is labeled ECON, not EV. It if were truly EV, it would be in that mode until the ICE took over when the battery ran too low, or the user selected Sport or HV mode. I guess an analogy would be a transmission with D (Drive) that picks a gear that the computer determines is correct for the current driving conditions. But if the transmission has manual gear selection, one could choose 3rd gear, for example, and it would stay in that gear whether or not it was correct. We should be able to disable the ICE if we choose to do so.
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  13. bobcubsfan

    bobcubsfan Active Member

    So, how does one select EV mode?
  14. M.M.

    M.M. Active Member

    Interesting documentation, although pretty broad. Based on the depictions of the climate control system, if what I've heard about the vehicle using a heat pump for heating while on battery is true, it looks like the car uses the same compressor for both air conditioning and heat-pump heating. Which I suppose makes perfect sense but initially caught me off guard since it's just using "AC" for it in the labeling. Assuming they haven't left anything out, this would confirm that both air conditioning and heat-pump heating run directly off the high voltage battery, and that there is no resistive heater available at all.

    Honda did a crap job of labeling drive modes and making clear what their use cases are, but I'm pretty sure if you asked one of their engineers they would tell you that any time you haven't selected HV or HV Charge modes, you've selected EV mode. Of course, since all three of the EV modes will turn the ICE on for max acceleration, and two of them will turn it on for unindicated amounts of moderate-to-hard acceleration, one could argue whether anything other than Eco/non-HV selected, or even that one, truly counts in the strictest sense.
    gedwin and Daniel M W like this.
  15. KentuckyKen

    KentuckyKen Well-Known Member

    It is somewhat confusing. Honda’s default is EV Mode, but the ICE can activate in certain conditions. You can control or mitigate but not totally eliminate ICE operation by selecting EV with Econ, plain EV, or EV with Sport in order of increased likelihood of ICE operation (unless you’re being very careful). If the very occasional and short ICE operation not due to traction/torque needs is abhorant to you, then you need a BEV and not a PHEV.

    I’ve been able to go 3 months/2,000 miles with no ICE usage (except for 4 short operations for System Check or battery mgt when fully charged) by driving in EV with Econ, moderate acceleration, speeds under 70 mph and no severe inclines.

    The other Modes are HV (again with Econ, plain, or Sport selected), and HV Charge which I have not used.
    Note that Plain EV amd EV with Econ will be remembered at next start up but Sport will not and will come up as plain EV at next start up.

    The Service Bulletins that AnthonyW shared were quite informative.
    I learned that:
    -the a/c compressor is a scroll type which is the most efficient type currently available.
    -the HV batteries are 168 3.7v Li-ion arranged in 12 cells in a pair of 7 modules with an out put of 311v
    -service can use an HDS to check the battery voltage and it’s deterioration status.
    -in engine drive mode, the ICE drives the wheels and the traction motor which charges the HV battery and the generator motor is not used.
    -not only the charging voltage, but also the battery output is limited in situations of excessive high or low SOC.

    I wonder if the last two could help explain why sometimes regen is limited and the ICE comes on right after being fully charged? M.M., can you use this new information in your hypothesis of how the regen works? It’s over my head.
    Last edited: Jun 1, 2018
  16. M.M.

    M.M. Active Member

    The interesting tidbit about it using the traction motor rather than generator for charging the battery while in engine drive mode is the only new thing, and thinking about it it does make sense to do it that way (it also implies that when the direct-drive transmission kicks in, it must decouple the ICE from the generator).

    My basic understanding of the logic holds; that the car considers 100% (as displayed in the app) pretty much a hard upper limit, so it will restrict regen somewhat at that point (probably to a current closer to what it is willing to put in at the tail end of the charge routine, to avoid too much self-heating), and will pretty quickly kick in whatever the ICE-braking routine is. It still seems a bit erratic as to exactly when it does this, and it's odd to me that they didn't leave at least a couple percent of overhead like the Volt does, but that seems to be the overall structure of what it's doing.

    I've got a question from the specs on gear ratios:

    Someone here commented that the Clarity PHEV uses a single fixed gear for the mechanical transmission. The specs show a gear ratio of 2.454, but then shows a final reduction of 3.421. I don't really know anything about automotive transmissions; can someone explain to me what that means, and why there are two ratios if it's a single fixed gear?

    This documentation doesn't look to explain the ICE+full-battery braking mode anywhere, which is what I was most curious about, but it does occur to me that if I'm understanding the math with the tire sizes correctly, the 14mph that I noticed an audible click and reduction in regen-paddle braking while in this mode would correspond suspiciously closely to an idle-esque 600rpm on the ICE; this could theoretically indicate that it's using the mechanical transmission to slow the car at that point. Or not. I don't really know what I'm talking about.
  17. LAF

    LAF Active Member

    modes seem pretty clear to me. around town don't do anything and the car will stay in EV as long as you have a charge, and when on the highway just push HV to keep charge the same so when you get to your destination you can drive locally in EV. If you find you didn't have enough charge on the battery on the road you can increase it by HV charge. Great flexibility.
  18. KentuckyKen

    KentuckyKen Well-Known Member

    M.M., if there were a Nobel Prize for reverse engineering, I’d say you were in the running for it.

    As we accumulate more observations of every day driving and more Honda sourced information like AnthonyW provided, I’m sure we’ll slowly but surely peel back the curtain on our wonderful Claritys. Wonderful because you can turn off your tech gene and drive it like any old car or go full geek and try to put the 5,000 piece puzzle together. Either way we’ve got a winner.

    So to paraphrase the Indy 500, “Gentlemen (and ladies), plug in your engines!”.
    clean.air@CA likes this.
  19. JimW

    JimW Active Member

    Typically, "final reduction" refers to the differential, the gear set that converts main driveshaft rotation to the half-shafts turning the front wheels, and allows them to turn at different speeds to navigate turns without scrubbing the tires. In the old days, you could select different ratios and could brag about having a "4.11 rear end" - the ratio is a tradeoff between acceleration and fuel economy.

    The other ratio is the gearbox which is lowering engine speed (and increasing torque) and sending power to the differential. These two gearboxes are in series, so you could multiply the ratios to get an overall ratio of engine speed to wheel speed.
  20. JimW

    JimW Active Member

    Thanks for posting these. I'm encouraged that it is so simple to remove and replace the center display. It would be great it they offered us an upgraded center display with faster performance and a volume control. Even better if they made it a free customer-satisfaction upgrade. This is honestly my only every-day complaint about this car. Is anyone at Honda listening here?
  21. AnthonyW

    AnthonyW Well-Known Member

    Yeah I agree that is pretty broad right now but it will get more specific with time. It seems that a lot of the info for a brand new car is patched together off of existing bulletins of the same type systems in other cars or previous year models. As time goes by, revisions are made and get very specific. I previously owned a 2006 Honda Civic Hybrid for 12 years and in the beginning I would go into the website once or twice a year and look for updated info. Reasoned that my cost of gas savings paid for the one day membership many times over.

    Agree with you on the no resistance heating at all, nor is any heat from the engine block utilized when the ICE is running and there is a call for heat.
  22. Viking79

    Viking79 Well-Known Member

    PHEV does not have heat pump, notice the diagram says for example only, parts may vary. Per my investigation here:
    It is clear it does not have a heat pump.

    It doesn't make sense for PHEVs to use heat pumps as it is cheaper to share coolant loop with ICE (as all heat pumps also need a resistance heater for low temperatures).
    KentuckyKen likes this.
  23. KentuckyKen

    KentuckyKen Well-Known Member

    I have to agree with Viking79 on this one. Per his research and this diagram from the Service Bulletins that AnthonyW. so kindly shared, it appears that the “electric a/c compressor” and the “electric coolant heater” are powered independently and separately from the battery heater (Canadian only) on the sub junction board. And besides, my heat comes on way too fast and hot to be delivered by a heat pump. So hopefully, and correct me if I’m wrong, we can lay the “US model has a heat pump” myth to rest.

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