Tesla battery article with info/tips on battery longevity

Discussion in 'Clarity' started by KentuckyKen, May 31, 2019.

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  1. KentuckyKen

    KentuckyKen Well-Known Member

    Here is an article I ran across on Tesla’s advantage in Li-ion batteries.
    It has a great graph on how temperature and depth of discharge affects battery longevity (# of cycles and capacity loss).
    The take home is that not letting your battery sit around for long periods at 100% is bad for battery health. Also, temperature extremes and depth of discharge are not conducive to battery longevity.

    I’m already using scheduling to complete charging just before I leave to next day to reduce the amount of time the battery sits at 100% SOC. Also I cleaned out the garage which along with many other benefits let’s my Clarity avoid some of the temperature extremes. And I don’t charge every night if I have enough range for the next day without going below 20% SOC. Probably not possible for you working or commuting stiffs. It’s a trade off between depth of discharge and time spent at 100% SOC. I wonder where the sweet spot is.

    Boy, I really wish Honda gave us the software option of charging to a specific % SOC for when we don’t need the whole range. For me, there are a lot of days I could get by with only charging to 80 or 90%.

    I’m curious what others are doing to try and keep their battery healthy with the least amount of degradation and range loss while still maintaining their needed range. Any other suggestions?


    Also attached as a PDF in case link goes down.

    Attached Files:

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  3. Clarity_Newbie

    Clarity_Newbie Active Member


    Typically my daily drive takes me down to 20-25% SoC.

    I default to a 9 hour charge cycle which translates to 85-95% max SoC most days.

    Occasionally I purposely run to SoC 0% and set charge time for 12hr 50 min which ensures 100% SoC. This allows for cell rebalancing etc.

    Essentially variable charge levels based solely on the previous day's driving. Effectively maintains additional buffer majority of the time. I don't stress about going to SoC 0 if my travel routine varies...if so that means I start with ~75% SoC the next time I drive. No worries.

    At 85-95% SoC I typically see
    40 to 45 EV mi in winter (40 degrees +- 10 degrees)
    52 to 58 in summer (80 degrees +-10 degrees)
    100% SoC sees
    42 to 48 winter
    60 to 65 summer.

    The Clarity gets driven ~two weeks a month on average.
    Last edited: May 31, 2019
  4. Sandroad

    Sandroad Well-Known Member

    But.......has anyone established for certain that the battery management system in the Clarity in fact has charged the battery to its full capacity when it stops charging. Or discharges it to 0 before the engine turns on. I think this linked article just revives the many threads/posts on here about what Honda did with the battery management system. And, yet another 3rd party "authority" writing in a web site what they think Tesla does with their battery management system, but not information directly from Tesla. Is this valid and reliable information? I'm as eager as anyone for information about the Clarity battery management system, but I still just plug in my Clarity when I'm done for the day and unplug it the next morning when I fire it up again, so to speak.
    MichiganClarity likes this.
  5. KentuckyKen

    KentuckyKen Well-Known Member

    AFAIK, no EV will allow itself to actually charge to 100% total SOC and discharge to actual 0% SOC since that would destroy the battery in short order.

    We can say that our Clarity’s BMS is protecting our battery from this since the most anyone has reported charging from the wall is around 14.1+ KWhs. So assuming the charger is around 92% efficient, that works out to about 76% of the 17kWh battery capacity. In other words, the BMS is reserving around 24% of the total capacity. We just can’t say for certain the split between top and bottom.
    I just wanted to know how many of us are trying to add a few % to these buffers to try to be even more kind to the battery and how it’s working for them.
    ken wells likes this.
  6. insightman

    insightman Well-Known Member Subscriber

    I drive. Then I plug-in (our Clarity, not me).

    Perhaps my the-battery-should-do-its-job attitude is responsible for my Insight's sad plight:
    I found out today my dealer will replace the HV battery in my beloved gen-1 Insight for just $4200. The AC compressor died over the winter, too: $1200. The stiff shift linkage: Honda no longer stocks the shift-linkage cables for this 13-year old car--"try a 'recycling' yard"! Next week I'll be ordering a Bumblebee HV battery and then contacting a "recycling" yard for both an AC compressor and shift-linkage cables. I am now going online to seek out and contact "recycling" yards. Oh look, a used AC compressor goes for just $70-$161.

    More shocking: My dealer replaced the two HV batteries in a 2014 Accord Hybrid (a model not sold in the mid-west AFAIK) for $17,000! Just the battery shipping was $1400!!! The 4-foot high battery crate from Honda also contained a set of special battery-replacement tools! The phrase "diminishing returns" comes to mind (only for the Accord, I'm too stubborn to abandon my Insight).

    You'd think that after burning through two IMA batteries in 13 years I'd be more anxious to treat my Clarity's battery with kid gloves, timing the individual time-to-recharge for 2 bars, 3 bars, 4 bars, 5 bars... and protecting the battery from fully recharging. Nope, too much trouble--the battery should do its job!
    Last edited: Jun 1, 2019
    Texas22Step and MPower like this.
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  8. 2002

    2002 Well-Known Member

    Yeah how neglectful. If only you didn't wittingly abuse your poor Insight battery by enjoying the car without thinking about the helpless fragile battery that was depending on you for its well being. If only you had treated said pitiful battery with more respect you probably would have used up only one IMA battery in those thirteen years instead of two. Meaning by simply thinking of someone (or I should say something) other than yourself you would have saved $4,200 in those thirteen years. Which works out to $323 per year, or $27 per month, or ..... hey wait a minute, I know people who spend more than that each month on popcorn at the movie theater. Nevermind, continue enjoying your car.
    Texas22Step, MPower and insightman like this.
  9. MrFixit

    MrFixit Well-Known Member

    Well, I hope there is enough production volume for the Clarity so that the 3rd party suppliers become interested in producing parts (including things like A/C compressors and traction battery replacements). Dealer pricing for parts (even with high volume vehicles) has always been outrageous and will likely continue to be.

    This is my biggest fear with the Clarity. When production stops (could be sooner rather than later), parts will be unavailable from a practical standpoint, and what little availability exists through the dealer will be totally unaffordable. Many repairs will essentially "total" the vehicle from a cost standpoint.
  10. insightman

    insightman Well-Known Member Subscriber

    Honda has discontinued offering some of the parts for my 13 year-old Honda Insight which essentially gave up the will to live in the past few months (HV battery, A/C compressor, shifter cables, O2 sensor). The engine seems OK (why did I even mention that?) But it's not just parts availability that matters, it's also the cost of those parts. I must admit, I haven't had to spend much money maintaining my Insight for the past 13 years, so I'm trying to look at my situation from an amortized point of view.

    I've been scouring the net for the discontinued replacement shifter cables. I just ordered a set online and hope the parts dealer actually has them in stock ($224). Honda's replacement HV battery (I assume it's remanufactured) is $2,391 (dealer says $4200 installed!), but Bumblebee batteries sells remanufactured HV batteries for $1100 and I can change it out. Battery remanufacturers will likely offer replacement batteries for the Clarity, too (likely more expensive than $1100). A/C compressors can be rebuilt, too (I'm about to buy a refurbed one for my Insight instead of a $1200 Honda replacement). Should I be happy that Honda still offers the oxygen sensor for $472? There are aftermarket O2 sensors for $195.
  11. David in TN

    David in TN Well-Known Member

    According to my ScanGauge II, mine fully charges to 100% SOC; however, it normally switches over from EV mode with about 11% SOC remaining. I can play with it, and have got it down to 8.6% SOC before there is no more blue available to run in EV.

    I have no idea if the parameters input in for the PID take into account any of the actual SOC or if it is "fudged" in some manner.

    It has previously been reported that only 14K of the 17K battery is usable.
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  13. HagerHedgie

    HagerHedgie Member

    I try to aim to leave 2-3 miles EV range left at the end of the day. I also try to avoid keeptit at 100% for any length of time. If I know I’m not driving much the next day I try not to charge it past 80%. I’m sure the system Honda designed does a good job conserving battery life but if I can get a few more cycles out of it by being anal then why not.
  14. Robert_Alabama

    Robert_Alabama Well-Known Member

    Many O2 sensors are not too big a pain to change out. Of course I don't know anything about the Insight and whether it is a pain to get to. I have had good luck in the past with aftermarket O2 sensors. If it isn't a big pain to get to, I'd change it myself and use aftermarket. Many cars have O2 sensors front and back in the exhaust system (before and after the catalytic converter). You may need to know which one or you will have to change both... If you can get the car up in the air so you can get under it, you should be able to locate and decide if you want to do it. Also, these things can be a beast to break loose as the threads tend to rust/seize due to the heat.
    insightman likes this.
  15. Sandroad

    Sandroad Well-Known Member

    Strong argument for a Honda extended warranty! I fear the "totaling" of a vehicle due to repairs will happen to many brands. Anyone who has looked at the OEM parts costs for the Clarity has come away staggered and shocked.
  16. AlAl

    AlAl Active Member

    We had a clarity come into my shop. It needed four new wheels, cradle, fender, both right door shells, various bumper components and suspension parts. Totalled due to cost of parts equaling over $24k.
    We were honestly expecting the procedure to cost ~6-8k, but some of the parts on this car are astronomically priced; cradle $3k, wheels $4k, Bumper and lights $8k. The sheet metal was cheap by comparison..
    My guess is Honda has no incentive to keep these cars on the road, other than meeting state compliance. It's a shame, because I was hoping features like V2G make it to this car, further expanding its utility.
    Lowell_Greenberg likes this.
  17. bpratt

    bpratt Active Member

    Before I purchased my Clarity in December 2017, I did a lot of looking at articles on lithium ion batteries. Unlike other rechargeable batteries, lithium ion batteries voltage reduces as it discharges. At 4.2 volts, the battery is considered to be at 100% charged. An article I found back then (I don't know where I got it) showed that the Clarity battery was considered full at 3.7 volts or 88% of the 4.2 max. Attached is a summary of that article followed by a second article that shows how EV manufacturers might handle lithium ion battery capacity fade over time. The numbers in that second article do not apply to the Clarity, just an example.

    Attached Files:

    KentuckyKen likes this.
  18. KentuckyKen

    KentuckyKen Well-Known Member

    Thanks for the battery info, @bpratt. That would seem to argue for the BMS having approximately the same buffer (around 12%) at top and bottom of the 17 kW total capacity. (That’s assuming 14.1 kW max total input at 92% charger efficiency.)
  19. Mike95465

    Mike95465 Member

    Based on the target for the onboard charger being 4093.8 mV and most lithium ion batteries have a max voltage of 4.2V, it seems like Honda is right around the 97% SOC. “Cell Voltage Limit while plug-in charging” is 4139.8 mV which creeps up towards 99% SOC.
    Whoever manufactured the batteries may have done something to increase the theoretical upper voltage limit though.

    Either way, I’m not stressing it. I charge from empty to full maxing out on 32A Level 2 at least twice a day. This is my 3rd hybrid and I’ve never babied any of them easily hitting 200k miles. My 2010 Honda Insight had 270k miles when I sold it and absolutely zero issues with battery, still hitting 43mpg in the end. I’m hoping for similar results from this Honda as well.

    Sent from my iPhone using Tapatalk
    MPower likes this.
  20. Lowell_Greenberg

    Lowell_Greenberg Active Member


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  21. Lowell_Greenberg

    Lowell_Greenberg Active Member

    This is interesting. What it suggests is that while the battery may compensate to maintain effective range, there is a deleterious and accelerating negative impact on battery life as it ages. Of course, the goal would be to still maintain a battery life and suitable range for the effective life of the car- which I always thought was targeted at 200k. But maybe 200k is no longer a goal of auto manufacturers. But to the extent they care about quality to aim for any less will probably damage brand satisfication.

    The Clarity in general is an interesting mishmash of parts bin and brand new parts and design. Hopefully it will hold up well and Honda will back it.

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