SOLVED- Unexpected ICE Turns On

Discussion in 'Clarity' started by AnthonyW, Sep 25, 2018.

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  1. AnthonyW

    AnthonyW Well-Known Member

    I am pretty confident that I have discovered why the ICE turns on after a full charge and other situations such as going down a large hill. While waiting for flight this past weekend, I decided to take a look at Honda patents. I stumbled upon "US10011270B2 Apparatus and method of controlling vehicle".

    The short answer is that the car is protecting the battery when it is fully charged, or when the battery can't accept the amount of charge that is being generated at that moment in time, while still maintaining full use and functionality of the braking system. It basically dumps extra energy to the generator which tries to dissipate it as heat and if that is not enough, the generator powers the ICE. See the pictures below. The first two are from the patent and the third is from the document "Electric Powertrain System Desc 3107 :



    For reference, I believe that MG1 is the traction motor, MG2 is the generator motor and the engine is the engine. Below are two snippets from the patent explaining what is going on:

    ...In this system, in an almost fully charged state where the regenerative power cannot be returned to the battery, the drive motor generates heat from the generated power and consumes the power, thereby compensating for insufficient regenerative braking force...


    ...and an engine reverse drive unit (inverter controller) that drives the engine by supplying part of regenerative power outputted from the drive motor to the motor generator. The regenerative controller can continue the regenerative braking even when all the regenerative power cannot be charged into the battery...

    Disclaimer: I cannot specifically tie this particular patent to the Clarity, but it all sure adds up. Both the patent and and the Electric power train description are attached. Please feel free to look over and give your take on the information. Lastly if you want to look for patents yourself it is very simple:

    Go to:
    In the search box type: assignee:(Honda Motor Co Ltd)
    You can add a keyword in the search if you want. In this case I searched: assignee:(Honda Motor Co Ltd) lithium

    Attached Files:

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  3. David A

    David A Guest

    Atta Boy! I admire the "sticktuitiveness"

    Makes sense to me.
  4. AnthonyW

    AnthonyW Well-Known Member

    The frowny faces are not intentional. It is supposed to be the word "assignee", then a colon, then an open parenthesis with now spaces in between. Don't know how to stop the automatic conversion to the frowny face.
    Randy Stegbauer likes this.
  5. KentuckyKen

    KentuckyKen Well-Known Member

    AnthonyW scores again. I now confer on you the Order of Clarity Master.
    I think you have finally found evidence to substantiate @insightman ’s most plausible theory on this. Here’s the quote for @insightman: “power consumed by engine reverse drive”.
    @insightman is now awarded the inaugural Clarity Reverse Engineering Award.
    That second doc is extremely informative and will give us a ton of info on the drive train system.

    This also explains why the ICE doesn’t come on every single time you’re at full charge and have a downhill or significant regen due to braking.
    I would have never thought to search patents for this. Well played sir, well played. We all owe you one (more).
    Last edited: Sep 25, 2018
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  6. AnthonyW

    AnthonyW Well-Known Member

    Thanks KentuckyKen. Very kind words. :) I work closely with the R&D department at my company and the standard practice apparently when you have something new and cutting-edge you try to get a patent for everything. My flight was delayed a good while so I decided to just looking around. :)

    Sent from my iPhone using Inside EVs
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  8. AnthonyW

    AnthonyW Well-Known Member

    Wow. I have been behind on the blog so I missed insightman pretty much nailing it 5 days ago in the other post. He figured it out without having to read poorly translated patent documents (come on Google, step it up). :) Thanks KentuckyKen for giving credit where credit is due. Insighman is the man here. :)

    Sent from my iPhone using Inside EVs
  9. KentuckyKen

    KentuckyKen Well-Known Member

    So are you. It’s a team effort to figure out our Claritys.
    Many took the time to post their experiences giving @insightman the facts he needed to puzzle it out and then you did the detective work to find the proof for the theory and give us even more info.
    Honors to all!
  10. insightman

    insightman Well-Known Member Subscriber

    In the patent description, MG2 is connected to the wheels, so it must be the traction motor ("drive motor" in the patent) and MG1 the starter motor/generator ("motor generator" in the patent).

    The patent says MG1 (the starter motor/generator) is "powering the engine" under regenerative braking when the battery is fully charged. The engine is described only as a "load." There is no indication the engine ever starts during regenerative braking. There is no discussion of MG1 reversing its torque to resist the running engine. The only reversal discussed is the reversal of MG1 from operating as a generator to operating as a motor.

    So what I read was a description of what happens in the i-MMD Honda Accord Hybrids and Insight when the battery is fully charged. It could be argued that running the engine in the Clarity PHEV is just an exaggerated case of presenting a load to the starter motor/generator, but the starter motor/generator would have to behave differently to use up the power from the traction motor when the engine is running.

    Alas, I didn't find validation of my theory that the Clarity PHEV's starter motor/generator reverses the normal direction of its torque while operating as a motor to resist the running engine during regenerative braking when the battery is full.

    Still, a very interesting document. Thanks AnthonyW for your searching expertise.
    Elm likes this.
  11. jorgie393

    jorgie393 Well-Known Member

    Wow, this is amazing. I am applauding from the sidelines.

    There is still one baffling thing: , even if the engine is used as a friction load (and even if burning gas happens, and is part of the plan to provide even more “load”):

    In this particular case, when triggered in this way, there is no reason whatsoever for the ICE to keep running after the braking stops, and even after thencar stops (as bobscunsfan and others have reported).

    I am developing a suspicion that the engineers who designed this fancy braking, and the engineers who programmed the “once ICE starts, keep running it until it warms up” didn’t quite work out the communication. So when the ICE is triggered by braking on a full battery, it invokes the “keep ICE running and burning gas until it warms up” path, even though that’s not necessary here.

    [This would be a true glitch]—but 100% speculation .
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  13. insightman

    insightman Well-Known Member Subscriber

    I'd like to know if the engine runs the same number of minutes regardless of how recently it was previously running. I should time an engine run while the weather is warm so I can compare its running time when the weather gets cold.
  14. Carro con enchufe

    Carro con enchufe Active Member

    My experience has been that if you’ve warmed up your engine and return to EV, and then call for ICE again (i.e. flooring it), the ICE turns off immediately after it’s not needed. The times that I’ve accelerated hard to get on a highway - if the ICE wasn’t on it runs for 5-10 minutes after merging, but if the ICE already warmed up it turns off as soon as I release the pedal.
  15. Clarity_Newbie

    Clarity_Newbie Active Member

    Anthony W...congrats on the thorough research and write-up. Admittedly I understand about 60% of the charts and language...but do get 100% of the gist of the write-up.

    MPower likes this.
  16. KentuckyKen

    KentuckyKen Well-Known Member

    I’ve had the same experience in HV mode on a long trip as @Carro con enchufe reports when flooring it. Definitely tries to shut off as soon as it’s warmed up and not needed anymore. It’s a very smart algorithm and explains why the EPA #s are so good.
    Carro con enchufe likes this.
  17. Steven B

    Steven B Active Member

    Oh, but it is necessary. There is documentation somewhere that "keep ICE running and burning gas until it warms up" is required to meet emissions regulations.
  18. jorgie393

    jorgie393 Well-Known Member

    Great point...Well, if that is the reason it is set up to keep running, then that makes perfect sense for the common case of using the ICE for power.

    But I wish that in the engine-braking case, which has been afflicting bobcubsfan and others, they had set it to just freewheel the engine without fuel, providing friction resistance [and, per AnthonyWs patent document Fig 3 above, some deliberately wasted heat by running the MG1 electric motor, that powers the engine, inefficiently on purpose]. Then emissions would not be an issue, since there would be none.
    Last edited: Sep 26, 2018
  19. weave

    weave Active Member

    I've been concerned about flooring it and kicking on the ICE when it hasn't been run for a while. Doesn't that stress the engine? Isn't it like starting up a normal ICE car and then flooring it before it warms up?

    If I know I'm going to use the ICE (like on a freeway) I usually go up the ramp on EV and wait until I'm at cruising speed and on a flat bit before I turn on HV, hoping it will at least engage the engine initially without a lot of RPM required.
  20. Steven B

    Steven B Active Member

    For those who choose not to stop the charging session prior to 100% and for those who are always heavy on the brake, maybe an aftermarket fuel shutoff valve can be installed and they can manually control whether gas is fed to the engine when the vehicle triggers engine turn on.
  21. su_A_ve

    su_A_ve Active Member

    Impressive. Most impressive.
  22. neal adkins

    neal adkins Active Member

    For those who are obsessed with the ice not coming on, why not just get an ev. In the big picture it's beneficial for the ice to run periodically. If not the oil will oxidize in engine before it looses viscosity. Also gas will go stale in the tank. Like it or not the ice compliments battery longevity by sharing the load and reducing the discharge rate of the smaller ev battery used in a phev especially when driving more aggressively. I personally like the way the my car performs and I use the different drive modes regularly.
    Thomas Mitchell likes this.
  23. insightman

    insightman Well-Known Member Subscriber

    The 0W-20 weight oil Honda's been using for engines since the first Insight provides instant lubrication when an engine restarts. However, it is probably not up to the task of lubricating a cold, unfueled engine as the engine is being spun by the Clarity PHEV's starter motor/generator for long periods of time (eg. while descending a mountain). So it makes sense to start the engine to warm up the oil when the engine is being used to resist the starter motor/generator as the starter motor/generator expends the excess electricity from the traction motor that the fully charged battery cannot accept.

    In contrast, in Honda's non-plug-in hybrids the engines are always warmed up, so they don't have to start those engines to get the oil warmed up to prevent damage as they spin the engine to provide a load for the starter motor/generator.

    Also, a running engine can provide more resistance to burn up more electricity in order to provide more regenerative braking for this 4,000-lb car.

    I've completely convinced myself about this scenario, but don't see anything about a running engine in any of the scholarly papers or the patent AnthonyW discovered.
    Walt R likes this.

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