Battery technology

Discussion in 'Clarity' started by JKroll, Sep 18, 2018.

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  1. JKroll

    JKroll Member

    Will the batteries fail to hold charge like my ipod, hand vacuum etc. after couple of years.

    What is different in rechargeable car batteries?
     
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  3. ab13

    ab13 Active Member

    The batteries are liquid cooled and designed for longer life due to the management system. They have a fairly long warranty also.

    • Emission warranty: Eight-year/100,000-mile or ten-year/150,000-mile Li-Ion battery limited warranty, depending on the state of purchase/registration
     
  4. KentuckyKen

    KentuckyKen Well-Known Member

    Here is a poor layman’s attempt at Clarity Battery 101.
    The Li-ion 17 kW traction battery is similar to ones in smaller applications and can be thought of as packaging more of the small cells together to gain higher voltages and capacity. This does mean that now we are talking about lethal Volts/Amperes being present in the car, hence the orange marking on high voltage wiring.
    The conditions that affect a Li-ion battery’s useful life in terms of longevity and ability to hold a charge are-
    1-extreme charging and discharging rates as in faster than a Level 2 charger or extended very high demand
    2-extreme temperature, especially high temps; and extreme temperature swings when fully charged
    3-over charging and to a lesser degree remaining at a full charge for extended periods
    4-full discharging to zero state of charge (SOC)
    5-failure to periodically balance the differences among all the battery cells

    Dems da bad news. The good news is that Honda has taken all that battery chemistry and physics into account in designing their battery management system (BMS):

    1-Level 1 and Level 2 charging does not approach the rate that will harm our battery packs and the Clarity does not accept any fast charging like dc or super chargers. So no worries here, although a few will argue that Level 1 is less stressful. I think the difference is too small to matter. And normal acceleration is not a problem, although I would avoid repeatedly runs at your local drag strip. Note that the Tesla’s and Leafs have limits as to how often they can dc or super charge on the same trip to protect their batteries. We don’t have to worry about this.

    2-With the larger size battery pack and the more rapid charge/discharge cycles, a liquid based cooling system is required and is why sometimes with the car off you may hear a “gurgling” sound as the fluid is circulated to a radiator under the hood. Also sometimes the radiator fan will come on for even more cooling. Unlike the Nissan Leafs that have no active battery cooling, Honda has designed our Claritys to keep their cool. And our Canadian friends even get a battery heater.

    3,4-Honda’s BMS appears to have adequately avoided the overcharging and full discharging problems quite well. You will notice that when your EV estimate reaches 0 and HV mode is called on, there are still 2 bars on the battery gauge. This is the buffer that protects the battery from being fully discharged.
    What about a buffer to keep the battery from being over charged? Here we have to speculate based on evidence reported on this forum. The most anyone has reported their EVSE delivered to the car charger is 14.1 to 14.4 kW and assuming the onboard charger (ac to dc converter) is, say, 90% efficient, then only about 12.5 to 13 kW is actually charging the battery.
    This means the usable capacity of the battery is around 73 to 76% of the 17 kW giving a buffer of about 27 to 24% split between top and bottom. This is on par with reports on other EVs and means you never fully charge or discharge the 17 kW battery pack. So no problem here, but some will argue that charging up to only 80% of the useful SOC is beneficial. I think it with the buffer already present that it makes such a small difference as to be unnecessary.

    5-The consensus seems to support that the BMS balances the cells at the end of a full charge. So no worries here as long as you periodically charge fully. (Lawyer required info: The manual states to fully charge the car before driving.)

    Add to the well designed BMS we have the fact that in California, the same battery pack gets a 10 yr warranty so it must be designed well or Honda would loose a lot of money in warranty replacements. BYW, Honda warrants the battery capacity to stay above 36.6 Ahr. This is about 2/3s of the nominal capacity of 55Ahr your start with. And in 8-10 yrs, I bet battery tech and prices will be dramatically better than now.
    So, batterywise, “Don’t worry, be happy”. (Insert Jamaican music here)


    PS:I am a molecular biologist and not an electrical engineer, or even a chemistry/physics guy. So I hope the EE experts will add to and/or correct the above which is just my self taught info and layman’s approach to this.
     
    Last edited: Sep 18, 2018
  5. JKroll

    JKroll Member

    holy cow ... kentuckyken .. hats off
     
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  6. Jason N

    Jason N New Member

    Now how do we who lease unlock that additional battery :)

    Sent from my Pixel 2 XL using Inside EVs mobile app
     
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  8. Heino

    Heino Active Member

    Great explanation! Thanks for the write-up!
     
  9. marshall

    marshall Active Member

  10. TheDom

    TheDom New Member

    Great write-up. I'd like to add that I've gotten as high as 14.87kWh as measured by my JuiceBox Pro 40. It doesn't change your point at all, just figured the extra datapoint would be useful to note.
     
    KentuckyKen likes this.
  11. KentuckyKen

    KentuckyKen Well-Known Member

    Thanks. Good to know. I’d really like to relate that to your Battery Capacity Signal. Did you get one in the new Pre-delivery Inspection doc? It would be in AHr and around 55 Ahr.
     
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  13. TheDom

    TheDom New Member

    Honestly I hadn't looked at the paperwork at all. I'll take a look when I get home.
     
  14. Ray B

    Ray B Active Member

    Great explanation, KentuckyKen. Very clear.

    Just a couple of thoughts on the topic of the battery.
    • The top end buffer is managed well by the BMS, but certainly over a long period of time that top buffer will get depleted and at that point the user may notice that the range begins to degrade. We have no idea when that depletion will happen - 10 years? 5 years? 15 years? My bet would be closer to 8 or 9 years on average. At that point, to maximize the life it would be prudent to avoid full 100% recharge as that will degrade the remaining life much faster than when a buffer still existed. It would be great if there was a way to know when the buffer is no longer functional. Or perhaps the BMS will just squeeze the middle portion of the SoC usage cycle and keep a little top end buffer forever.
    • I wonder if the restriction of 58% max recharging using the HV-charge mode could be another indication that full recharging (especially later in the life cycle when the buffer is gone) will wear it out faster. Just speculating.
    • I think the routinely keeping the SoC in the 80%-20% sweet spot may help to extend the life of the top buffer. But it may be insignificant. I would bet that the aggressiveness of the driver and the terrain plays a more substantial role. But I take the point about occasional full charging to 100% (it is really unavoidable - I'm not fastidious about the 80-20).
    • Are we certain that the last two bars of the battery meter (the only ones left when the EV range goes to 0) are the bottom end buffer? I wonder if there is a secondary charge after the EV drive is depleted that is used to maintain the 12V battery charged and run the ICE, but stays above the bottom end buffer. Again, just speculating. Maybe it is just the bottom end buffer, and the regen unit is used as a pseudo-alternator to keep up with the electrical demands when the main EV battery is depleted down to the bottom buffer.
    In any event, I agree with your conclusion that one should just enjoy the car and not fuss about the battery life. But I'm a nerd about these things and just want to understand what makes it tick.
     
    KentuckyKen likes this.
  15. TheDom

    TheDom New Member

    They did not list the Battery Capacity Signal on the inspection doc unfortunately.
     
  16. KentuckyKen

    KentuckyKen Well-Known Member

    Thanks for checking. Mine didn’t either. I made them pull it when I took it in the the underbody plugs. It’s the only way to know your traction battery wasn’t damaged by not being charged before you drove it off the lot.
     
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  17. TheDom

    TheDom New Member

    Just checked and it is missing the body plugs. I guess I'll do the same thing as you, although I'm not sure what recourse I'd really have if it did show a lower number 20+days out from taking delivery.
     
  18. Tailwind

    Tailwind Active Member

    To Ray and Ken,

    I would suggest that the last two bars of battery charge when EV range reaches zero are there more for HV mode than for battery protection from over depletion. Two points to support this theory:

    • The battery charge gauge shows the battery state as 100% charged without leaving the top two bars unlit. So why would they leave the bottom two bars visible? If they were going to show a protected zone, why not do it both ends instead of just one?
    • The car is a hybrid powered car and therefore has to have a high voltage battery to store the reclaimed energy from coasting and deceleration. All hybrid cars have such a battery, Prius, Insight, etc. In the case of the new Insight, it has been reported that it has a 0.9 kW battery. I would suggest that the bottom two bars of battery charge in the Clarity is the "hybrid battery". If you have ever driven your Clarity down to zero EV mileage, you would notice that in certain situations of low energy requirements, the car goes back into EV mode, even with zero showing as the EV range. Additionally, with zero EV range showing but operating in HV mode, at times, the motive energy shows as coming from both the engine driven generator and the battery. If the vehicle were protecting the battery from being totally discharged by stopping the battery from further use, why is the battery being used in those situations?
    I live in central Indiana where the biggest hill I encounter is no taller than about 50 feet vertical climb. I would ask those of you who live in mountainous areas if you have ever noticed the battery level drop to just one bar when on a long climb in HV mode when the EV range is zero. If that is the case, I would add that to my set of supporting facts to promote my theory.

    Just my thoughts on the last two bars of battery charge.
     
  19. Ray B

    Ray B Active Member

    Yes I think that sums up my view. The last two bars on the gauge are likely a kind of operational buffer, and beyond that there is an unseen battery harm avoidance buffer at the extreme low end (0 - ~10% of real SoC).
     
  20. insightman

    insightman Well-Known Member

    A supposedly fully discharged (2 bars) Clarity takes less than 15 kWh to recharge. Last 2 bars = 2 kWh protection buffer?

    It is a good question why Honda would display the bottom-end protection buffer unless there's some dire situation where that buffer is "violated" and the gauge really can show less than 2 bars.
     
  21. KentuckyKen

    KentuckyKen Well-Known Member

    Valid point @Tailwind, but no one has reported ever going down to no bars showing. Also, when you deplete down to 2 bars and 0 EV range, the algorithm may do a little give and take with the remaining SOC, but it tries not to go further down as evidenced by the increased likelihood of the angry bees. And HV mode on only 2 bars is a much poorer driving experience than when you have more charge available, especially on hills.
    So the last 2 bars may not be a 100% hard floor for the SOC, but they do indicate that the BMS will not let the battery be completely depleted which would be ruinous for a Li-ion battery.

    So in the interest of science, I’m going to take one for the team and let my EV range drop to 0 instead of charging and see how it acts in town. Sigh...I’ve been totally EV except for on long trip for the last 6 months. And I may even Work up enough nerve to try HV Charge!
     
    Last edited: Sep 22, 2018
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  22. Alantn

    Alantn Member

    Time to give the oil companies some of your cash @KentuckyKen or they'll break something :) Thanks for experimenting.
     
    Last edited: Sep 22, 2018
  23. Steven B

    Steven B Active Member

    When you completely deplete the EV range and then call on the system to provide additional power beyond what the engine can provide, it will further drain the battery. While 2 bars is supposedly "11%" per the app, I've seen it as low as 7 or 8 percent and I imagine it could theoretically drain lower than that if someone put it under heavy strain at 2 bars. I don't recall if it showed 1 bar at 7% but it may have.

    @KentuckyKen you should try to take it into the hill country at 0 EV and see how low you can get the battery percentage to go.
     

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