A real life example why charging to 100% is bad

Discussion in 'Clarity' started by oko, Jul 17, 2018.

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  1. oko

    oko Member

    Here's a nice article about a Tesla hitting 400K miles:


    Here's the relevant part:

    "Average battery degradation over the vehicle’s first 194,000 miles was around 6% with multiple Supercharger stops every day. Between 194,000 – 324,000 miles, the HV battery degradation was estimated at around 22%. According to Tesloop, this was likely due to the company’s practice of constantly charging eHawk to 95-100%, instead of Tesla’s recommended 90-95%".

    Note that they probably drive the car immediately after charging, so the theory "it is okay if you drive immediately after 100%" seems to be incorrect.

    I wish Clarity had the option to stop at 90%.
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  3. Odobo

    Odobo Active Member

    Comparing to charging to 100% instead of 95%, the multiple supercharge per day probably hurt it more. It's also interesting that the 2nd battery degrade more than the 1st one (22% compare to 6%).
  4. ClarityDoc

    ClarityDoc Active Member

    I don't know how the batteries might be similar or different, nor the details on how the Clarity manages charging above 90% of actual capacity. Do you?
  5. Hobbesgsr

    Hobbesgsr Active Member

    I thought Honda designed the battery management to not fully charge or deplete the battery.
    With this info, maybe I should lower the charge rate of my Juicebox to 24A.
  6. jorgie393

    jorgie393 Well-Known Member

    How do we know that the Clarity doesn’t already stop at 90%?

    I mean, the bars go to the top and the car stops accepting charge. But the engineers could very well have set that point to 90% of true battery capacity. Just as an empty bar with no more battery power available might not be 0% charge on the battery.

    Impression I had was that we knew at least on the bottom end the Clarity wasn’t using its full range, by design. Not sure about the top end, and I may have this wrong.
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  8. oko

    oko Member

    From all these discussions about ICE coming on when battery is 100% full, I assume that Clarity really charges up to 100%. Somebody tested this by driving down immediately after 100%, and he could consistently see starting the ICE.
    Kailani likes this.
  9. PHEV Newbie

    PHEV Newbie Well-Known Member

    You are right to want to do everything possible to increase battery longevity and keeping your charge within the 40-80% range is best so that means charging every chance you get instead of charging fully and then again after depletion. The reason is that the Clarity battery will degrade much faster than the Tesla. All Li ion batteries have a limited number of charge cycles. If the chemistry of the Clarity battery is similar to Tesla, you will observe the same degree of degradation at 30,348 miles as the S90D at 195,000. Why? Because the Clarity gets 47 miles per charge cycle (EPA # but we actually get more in real life!) while the S90D gets 302 miles per cycle. Thus, if you don't treat the Clarity battery well, your EV range will drop pretty quick. Don't feel too bad because this is a bigger problem for PHEVs with less range. There's a guy who's been chronicling his frustrations with the rapid declining range of his Outlander PHEV:

    He's pretty shocked but its really to be expected because he puts a lot of EV miles on his Highlander with a range that's much lower than the Clarity's (BTW, when he says 20 degrees, he means Centigrade so not very cold at all). This is relevant to anyone considering other PHEVs with limited range like the Prius Prime. Fact is that if you're able to stay EV most of the time and drive them a lot, the battery will degrade after a short amount of time.
  10. Viking79

    Viking79 Well-Known Member

    PHEVs and BEVs usually have different chemistries and design parameters. PHEVs are designed for many cycles of essentially DC quick charging and need to last thousands of battery cycles. A BEV might only need to last 1000 battery cycles so often charge to higher state of charge, etc.

    Charging to 100% is obviously bad, but no cars actually charge that high, most BEVs around 90-96% and most PHEVs around 80-85%. This in part is for above, the PHEV needs to last 5000 cycles or more, and also the engine when running can essentially DC quick charge the battery so it is best to keep it under a state of SoC where DC quick charging is safe when the engine is allowed to run. My i3 won't allow the engine to start until under 75% SoC as it can't sink that power anywhere but the battery or wheels.

    This is one of the better calendar aging studies I have seen for Li-ion: http://jes.ecsdl.org/content/163/9/A1872/F2.expansion.html
    And they indicate several other studies are flawed as they don't keep the SoC steady through the aging period (SoC changes as the battery ages). They show there are 2 distinct plateaus in aging, one below about 50-70% SoC (varies) and one above. This has to do with how the Lithium is stored in the cathode.

    Recommendations vary largely based on what your chemistry is. If you look at the results in that study and see dramatically accelerated aging for NMC stored above 95% and temps above 100F and then consider the Nissan Leaf used NMC chemistry, you might make a connection with Nissan Leaf Batteries in High Temp areas being problematic (and this study would predict that). Cars like the Volt use NMC as well, never charge above 85% and have shown essentially no degradation.

    An issue with not charging your car to full (Indicated 100%, not actually 100% in batteries) is features like cell balancing might not occur and those are critical to the performance of the battery. You might see temporary capacity loss if your cells never balance as you will be limited by the weakest cell. Some companies choose to balance at the top, others at the bottom, some do it during operation, but I think most cars only cell balance during the final stage of charging.

    My point with all this: Just charge your Clarity fully on a regular basis as the manual recommends.
  11. brady

    brady Member

    I charged my leaf everyday to 100% and after 3 years I didnt have any battery degradation that could be noticed on the dashboard or in my calculations. I figure that by the time we need new batteries they will be about 1/3 the price they are now. I will just buy a new one and go down the road.
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  13. KentuckyKen

    KentuckyKen Well-Known Member

    Amen, Viking.
    If you read that article carefully, you’ll see that the real problem with the accelerated deterioration was due to multiple Supercharger usage in the same drive cycle. Even Tesla cautions against multiple Supercharger charging since the battery management system can’t handle it. This is not an issue for our Claritys since our maximum charging is limited to a 32 Amp Level 2 EVSE.
    All I am doing after reading all the threads on battery life here is to schedule charging in the early morning to avoid charging a hot battery. And since almost all my driving is short hop local driving, I can almost always keep from running the SOC below 4 bars and not charge until I’m down to half set of bars.
    atr and Viking79 like this.
  14. oko

    oko Member

    Brady: Are you in cold climate? Have you used Leafspy to see the battery degradation? I guess having leaf 3 years and no battery degradation (even if you never did 100%) is something really unheard of (I am a 5.5 years leaf owner and have been active in Leaf forums for 6 years :)). My battery lost its first bar at only 18K.

    Also, have you seen the discussions over the Leaf forums about battery price? Nissan increased the price of the battery replacement recently.
  15. Atkinson

    Atkinson Active Member

    Driving long distances with multiple fast charges to the extreme end of battery capacity is hard on the chemistry.
    The only way to make that scenario worse is to do it in extreme ambient temps.
    Clarity's can't fast charge, but if you run hard in EV mode at the high or low end of the temp scale, you might reduce battery life.
    Without fast charging, you can't keep the abuse up all day (if that's what you do).
    There is a 2.5 hour cool down.
    Drive nice and the car will last forever.
    atr and dstrauss like this.
  16. dstrauss

    dstrauss Well-Known Member

    Folks, is there any proof, one way or the other, that charging to 100% of the dash scale is actually 100% of the capacity of the cells? I've read a lot of conjecture that the system itself tops somewhere north of 80%, with about a reserve for 20% during hybrid operation. The Tesla story really smells of charging too fast and too frequently. There are many cases of 200,000 mile plus Prii (plural of Prius) in personal and taxi service with very little battery degradation.
    insightman likes this.
  17. brady

    brady Member

    I live in Oklahoma, summers top 105 easy. No I didn't use leafspy, but my point is that I didnt have a noticeable drop in battery performance. At end of lease I had 28K and no bars dropped off the dashboard. I would suspect battery prices are going up due to all the people buying the older leafs for a song and upgrading the battery pack (supply and demand). Battery prices worldwide are falling fast overall. In as many years it takes for the clarity to need replacement the battery will be 1/3 (probably $1000) of what it is now ($3400 for 17kw @ $200 a kw).
  18. PHEV Newbie

    PHEV Newbie Well-Known Member

    The Clarity's battery warranty is 8 years/100,000 miles but Steven B notes that Honda doesn't consider the battery defective unless it is down below 25% of original capacity. That seems awfully low to me but it seems that Honda has determined that loss of 75% capacity is normal wear and tear after 100,000 miles.
  19. dstrauss

    dstrauss Well-Known Member

    What THEY consider a defect and what CUSTOMERS/COURTS consider defective can be two very different matters.
    lorem101 likes this.
  20. Pushmi-Pullyu

    Pushmi-Pullyu Well-Known Member

    That's the right question. Tesla's BEVs leave only a very small percentage of reserve at the top. (That is, the difference between full capacity and usable capacity.) I've seen a plausible claim for 4-6%; apparently some of Tesla's different sizes of battery packs are designed to have more reserve than others, for some strange reason; or at least that's what those analyzing Tesla's packs claim.

    All PHEVs should reserve considerably more than that at the top, and probably do.

    Keep in mind that when your instrument panel says the Clarity PHEV's battery pack is 100% charged, that's only 100% of usable capacity. It's not 100% of full capacity.

    Also keep in mind that the Clarity PHEV isn't the Tesla Model S.

    Anything else I'd add on the subject has already been covered very well by Viking79 in his excellent post #8 above; he covered the subject considerably better than I would have.

    Last edited: Jul 18, 2018
  21. Pushmi-Pullyu

    Pushmi-Pullyu Well-Known Member

    I don't know how much reserve the Clarity PHEV uses in the pack, but 20% sounds plausible. Some claim the Volt uses 30%, but after doing some research and math on that, I think that may be an exaggeration.

    Anyway, I doubt anyone here can "prove" that the Clarity PHEV does not allow the pack to be charged to 100% of what the cell manufacturer lists as name-plate capacity for the cells, but any EV engineer would be incredibly stupid to design any EV battery pack (BEV or PHEV... or heck, even non-plug-in HEV) to charge to 100% of name-plate capacity. Repeatedly charging to 100% and/or discharging to 0% wears out li-ion batteries quite rapidly indeed. Furthermore, A PHEV like the Clarity will have a greater percentage of reserve at the top than a BEV like the Model S, because a PHEV's smaller battery pack must withstand more frequent cycling. Viking79 talked about this subject in his excellent post above.

    So EV engineering principles and common sense says no, 100% of usable capacity is not 100% of full capacity. It has to be somewhat less. I can't prove it; EV makers keep details about their battery packs as trade secrets, so Honda isn't going to tell us, any more than Tesla or any other EV maker does. But I'm pretty confident that's true.

    rickyrsx likes this.
  22. Atkinson

    Atkinson Active Member

    Depending on the state your Clarity was registered and driven in the emissions warranty can be 15 years/150K miles
    Attached Honda warranty.
    In Mass (and all California Emissions states), the doc references a battery assembly warranty of 10 years/150K miles.
    This is the first I've heard of a 15 year/150K mile warranty on anything.
    Any California Clarity owners have details?

    Attached Files:

  23. bpratt

    bpratt Active Member

    Clarity and Tesla use different types of Lithium-Ion batteries and charge them differently. Tesla uses a Lithium Nickel Cobalt Aluminum Oxide battery which provides very high output per weight but has a low # of charge cycles life. It will also allow for a high charge rate. Clarity uses a Lithium Nickel Manganese Cobol Oxide battery which provides less output per weight but has about 4 times the # of charge cycles life. The Clarity battery does not allow for a fast charge.
    Most LI batteries have a maximum voltage charge of 4.2 volts. Tesla allows their battery to be charged to near 4.2 volts where the Clarity only allows the battery to charge to 3.7 volts or about 88%.
    One of the newest and safest LI batteries is the Lithium Titanite battery which has 3 times the charge cycles of the Clarity Battery and up to 14 times that of a Tesla. However, it has a lower output per weight than the Clarity or Tesla batteries, but it does allow for the fastest charge rate. It is currently used in the Honda Fit. The Clarity battery has a voltage range of 3.0 Volts to 4.2 Volts where the Fit battery has a range of 1.8 Volts to 2.85 Volts. If the voltage in a cell drops below that minimum range, the battery will be damaged. If the voltage rises above the maximum range, the battery could explode or catch fire.

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