Monitoring battery health

Discussion in 'Clarity' started by FrameFlipper, Dec 19, 2017.

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  1. FrameFlipper

    FrameFlipper New Member

    Like Viking79, I'm also seeing about 35 miles of EV range on the console at 100% charge -- outdoor temp is about 40F. (2018 Honda Clarity PHEV Touring)

    I don't see where Honda has included a means of gauging HV battery health. (Hopefully this is not a strategic omission.)

    I seem to recall Leaf owners in a forum discussing an aftermarket system from FleetCarma that plugs into a vehicle’s OBD-II port. I believe the idea was to collect & share performance data within the owner community.

    Question: has anyone identified options that Clarity-PHEV owners can use to monitor battery health/degradation over the lifetime of their vehicles? (Outside of Honda's computed range, and the actual EV miles driven per charge.)

    Obviously, this may present more of a concern for owners than lease holders.
    Tony Vo likes this.
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  3. Pushmi-Pullyu

    Pushmi-Pullyu Well-Known Member

    I think you'll find that no EV maker makes it easy to get that info, so probably no reason to think Honda is any worse about that than anybody else.

    Exactly what is it you are trying to measure? You can install a meter between your home's electric supply and the EV charger which will give you a true reading of how much electricity you're using to charge your car (including losses from charger inefficiency), so you could compare that to miles driven to get a true measure of miles per kWh.

    But trying to use, for example, a volt-meter to gauge a battery pack's state of charge is pretty useless, for various reasons. One reason is that charge does not drop off as a straight function of voltage; voltage stays pretty flat until the battery is almost exhausted, then it drops off a cliff. Another problem is that the battery's capacity varies by temperature... and it varies a surprising amount by temperature, not just a little bit!

    Some discussion of the issues on the Tesla Motors Club forum (link below), but to quote one of the posts: "It's very difficult to measure the true battery capacity."

    Of course this discussion is specific to Tesla cars, but if you do the research I think you'll find most of what they say applies to all plug-in EVs.
    Last edited: Dec 19, 2017
  4. JyChevyVolt

    JyChevyVolt Active Member

    The Guess of meter will change after a couple of charge and discharge.

    The Clarity PHEV uses 13.5kWh out of 17kWh. You'll be fine.
    Last edited: Dec 19, 2017
  5. Viking79

    Viking79 Well-Known Member

    What I do with my Volt is just monitor how many miles it drives in similar conditions with a full charge. I don't think it takes off battery bars or anything like the Leaf did. Given that it is liquid cooled and a modern battery I would hope it would last the useful life of the vehicle. Do we know who makes the cells for Honda though? I know any Volt failures have mostly been battery electronics or maybe a faulty cell, not failure due to degradation, and there are Volts with 2500 to 4000 cycles in their batteries.
  6. jaymac

    jaymac New Member

    The Clarity PHEV has liquid cooling for the battery ?
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  8. Viking79

    Viking79 Well-Known Member

    Yes, it has coolant loops for engine, HV Battery, and inverter. I think it was page 490 of full owners manual that talks a bit about the coolant loop for HV battery. It should be good for hotter climates, liquid cooling is better at removing heat than forced air.
  9. FrameFlipper

    FrameFlipper New Member

    Thanks to all for your posts. As a newbie PEV owner, I'm admittedly on a steep learning curve here.

    Viking79: yeah, I recall reading Leaf owners describe a built-in degradation measurement that Nissan provided,

    What intrigued me about this is that as a consumer, you've access to evidence that provides an approximate measure of battery condition at time of delivery, and throughout the battery pack's lifetime. The utility of this manufacturer-provided metric from a warranty and re-sale perspective seems significant.


    "Nissan LEAF Gets Replacement Battery After Mysterious 4-Bar Loss In 4 Months"
    (“Kudos to Nissan Motor Corporation for having the insight to create the paper trail that allows us to know the true nature of the battery’s health. It was the warranty history on the car that provided the proof to warrant the test needed to complete the escalation process.”)

    "A Second Life for Electric Vehicle Batteries: Answering Questions on Battery Degradation and Value"
    ("Installing hardware and software capabilities onboard the vehicle that can both estimate remaining battery capacity from in-situ measurements, as well as track average battery temperature over time, will thereby help facilitate the second use of automotive batteries")

    While I recognize we've come a long way from Leyden jars, I'm dubious about there's something so complex about modern storage cells that makes measuring battery degradation impractical. A PEV's embedded controllers have access to a wide array of data, including temperature and dynamic load characteristics.

    I admire Honda's commitment to quality and reliability. I am however, a little concerned about dealer PEV education, and their willingness to act on battery degradation issues down the road in the absence of a manufacturer-provided metric.

    In the absence of a manufacturer-provided measure of battery degradation, how does the consumer know:
    1) that a new PEV's battery is not defective or damaged (through improper storage/use prior to sale, etc.)?
    2) whether or not a previously sound PEV's battery is degrading prematurely and eligible for warranty action?
    3) whether a used PEV is worth it's price (a topic covered in the Lawrence Berkeley Lab article above)?

    Again, admitted PEV newbie here -- so sorry if I'm missing something fundamental, or previously covered in this forum.

    Attached Files:

  10. Pushmi-Pullyu

    Pushmi-Pullyu Well-Known Member

    Unfortunately, the short answer is: You won't know.

    Even if you went to a Tesla CPO store and asked for the info in the car's computer and/or BMS about how much the battery has degraded, I doubt they would give you access to that info. But perhaps they would tell you what the instrument panel reads as the range when fully charged.

    In other cases, buying a used EV... all I can say is Caveat emptor: Buyer beware!

    Nothing at all to apologize for. You have raised some very important questions, and ones certainly worth discussing. Unfortunately you are also opening one just one, but several cans of worms. The answers will not be straightforward, and even those with training and experience as electrical engineers may not agree on the answers.

    If you really want to dive into this subject, I suggest you start here:

    And if you are really determined to educate yourself thoroughly on the subject, you can read some or all of the hundreds of posts in the discussion here:

    Be warned that while Tesla Motors Club forum member "wk067" clearly has experience as an electrical engineer, he makes some assumptions about the way that battery manufacturers (in this case, Panasonic) rate (or measure) the capacity of their batteries. But it's quite likely that not all of his assumptions are correct, as you'll see if you read far enough into the discussion. So keep in mind that when he claims Tesla is misleading or even "lying" about the actual capacity of its battery packs... he's expressing his opinions as if they are established facts, which they are not.

    I apologize for all this being oriented toward Tesla's cars and not Honda's, but this is the info I personally know most about, and there is a heck of a lot more info available on Tesla's cars, and technical discussions of them, than there are about most other EVs. You might also do well to look at the archives on the forum, but I personally am not familiar enough with that forum to be able to easily find discussions on specific subjects there.
  11. FrameFlipper

    FrameFlipper New Member

    Pushmi-Pullyu, thanks for the helpful info!

    I'll gather up my courage for a deep dive into the discussion threads you provided. :)
    Tony Vo likes this.
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  13. JyChevyVolt

    JyChevyVolt Active Member

    Battery in PHEV and BEV are handled differently. Your really not discharging the battery fully since there's a significant buffer in the lower and upper region, in the PHEV. Honda is using 13.5kWh out of 17kWh.
  14. Pushmi-Pullyu

    Pushmi-Pullyu Well-Known Member

    Yes, he would do better to find a discussion at the GM-Volt forum covering the technical issues of measuring battery pack capacity, and capacity loss over time. As you say, discussion of Tesla's cars will concern only BEVs, which differ in some important ways from PHEVs.

    Is anybody familiar enough with the forum to point him to an in-depth and well-informed discussion of the issues?
  15. JyChevyVolt

    JyChevyVolt Active Member

    After doing the calculation, the Clarity PHEV uses 12 kWh out of 17 kWh. OP should not worry about battery degradation.

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