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Charge every drive or just charge daily?

Discussion in 'Model S: Battery & Charging' started by balefire, Dec 28, 2013.

  1. balefire

    balefire Member

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    #1 balefire, Dec 28, 2013
    Last edited: Dec 28, 2013
    Just curious
    In order to maximize battery longevity, should I charge every drive (i.e. multiple short trips in one day), or charge daily?
    This assumes I'm NOT charging to max but to only 80 or 90%
    Thanks!
     
  2. scaesare

    scaesare Active Member

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    As you said the trips are short, I'd suggest a daily charge regimen.

    The things that induce some wear/degradation on Li-Ion batteries:

    1) Maintaining 100% charge state for extended periods
    2) Complete discharge (0%)
    3) Charge cycles
    4) High temps

    So if charging to 80-90% provides you sufficient range for your daily driving needs, then you can avoid excess cycles on the pack and yet still not have to max charge.
     
  3. Chipper

    Chipper Active Member

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    To quote the old adage: A plugged in Tesla is a happy Tesla. But personally I just plug mine in at the end of the day.
     
  4. jerry33

    jerry33 S85 - VIN:P05130 - 3/2/13

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    Cycles in this instance means full cycles. Many small cycles increase life.
     
  5. balefire

    balefire Member

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    This is true with my cell phone. And what I was alluding to.
    I was not sure if the same is true with our complex battery of our car.
     
  6. ViperDoc

    ViperDoc Roadster 1305

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    Charging

    We mostly drive around town, so we charge to the lowest level we can (about 50%) and plug in every night. It should maximize longevity, but then you need to remember to up the limit if you are planning a trip!
     
  7. Raffy.Roma

    Raffy.Roma Active Member

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    Good to know this.
     
  8. jerry33

    jerry33 S85 - VIN:P05130 - 3/2/13

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    LiIon attery chemistry is LiIon battery chemistry to a certain extent. My understanding is that it's best for the battery to drive between 90% and 50%, to store at 50%, and to reduce the range of charge whenever possible. LiIon batteries fail due to microcracking. Drawing current at low SOC, storing at high SOC, and large cycles are the main causes of non-time-related microcracks.
     
  9. yobigd20

    yobigd20 Well-Known Member

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    You should charge every chance you get. Even if you have many short trips, you should plug in every chance your at home. if you charge 5% 6 times this is WAYYYYY MUUUUUUCHHHHHHHHHH better than one 30% charge. The smaller/shorter you can keep those cycles, the much better for your battery.

    I have 33k miles on my MS and I have rated range numbers significantly higher than most people. I was still getting 265 rated range at 26k miles. I ranged charged accidentally last week (forgot to set it lower after pre-warming the battery that morning) and had to go back out later and it was at 255mi and still charging. I also charge at lower amps, usually 20-25A on 240V.
     
  10. mknox

    mknox Well-Known Member

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    I charge daily unless I have the opportunity for some free electrons when I'm out.

    In summer, I typically charge to 70% and am at about 30% at the end of the day. In the winter, I charge to 80 or 90% and still end at around 30% due to the extra energy I use in the cold.
     
  11. scaesare

    scaesare Active Member

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    No cycle, no matter how small, increases the life of a Li-ion. However, you can prevent as significant a decrease in cell life by carefully managing cycle depth versus number of cycles.

    While shallower charge cycles are indeed better, the number of cycles is also a factor. Discharging/charging a Li-ion cell 50% once can be better than discharging/charging it 25% twice.

    You can read about it here: Battery University. If you look at Table 2, approximately doubling the number of charge cycles is worse then simply discharging to twice the depth at just about each step. Obviously we know 100% and 0% are no-no's, but it holds for the ranges in between.

    As the original poster suggested 80-90%, and most people don't drive down to zero, but often leave themselves a 20-30% buffer at the low end, I wouldn't be inclined to induce charging 2-3 times as much instead of a single discharge from 80% down to 30% or so...
     
  12. AmpedRealtor

    AmpedRealtor Active Member

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    #12 AmpedRealtor, Dec 28, 2013
    Last edited: Dec 28, 2013
    Except for this, from page 83 of the Owner's Manual:

    There is no advantage to waiting until the Battery’s level is low before charging. In fact, the Battery performs best when charged regularly.

    Also good to know, from page 84 of the Owner's Manual:

    Note:
    Whenever Model S is plugged in but not actively charging, it draws energy from the wall instead of using energy stored in the Battery. For example, if you are sitting in Model S and using the touchscreen while it’s is parked and plugged in, the energy being used is drawn from the power outlet instead of the Battery.
     
  13. jerry33

    jerry33 S85 - VIN:P05130 - 3/2/13

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    In this case "increase" means increased life compared to large cycles. Sorry, I wasn't clearer.
     
  14. 772

    772 Member

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    For an equal amount of charge, many smaller cycles are better than a few larger ones. I'd plug in whenever it's convenient to do so instead of waiting.
     
  15. scaesare

    scaesare Active Member

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    This isn't necessarily the case. See my post above with some citations regarding charge cycles.
     
  16. yobigd20

    yobigd20 Well-Known Member

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    You're wrong. You are misinterpreting that chart.

    A full discharge cycle is from full then depleting your entire battery and charging it back up to full , or in other words using all 85kW of your battery before plugging in and charging it back up to 85kW. In Table 2, as described if you do this 100% depth of discharge, the battery will only last 300-500 of these "full discharge cycles" before it's capacity drops to 70%. If you only ever do 10% depths of discharge, the battery will be able to handle the equivalent of 3750-4700 full discharge cycles before the capacity drops to 70%. To put this in numbers, if a full cycle uses 85kW, then if you always go from 100% to 0% then your battery is going to use a max of 500x85kW before the capacity drops to 70%. But if you only ever do 10% depths of discharges, you can do these little 10% chargers many many many many many many many times and your battery will be able to handle about 4700x85kW of energy before the capacity drops down to 70%. That second column describes how many equivalent "full discharge cycles" it can handle. Obviously, the smallest DoD you can do the better. This allows you to use/pump much more energy through the batteries life vs if you only did 100% depths of discharges. As the chart says, these partial discharges reduces stress and prolong battery life. The shorter the discharge (low DoD), the longer the battery will last. If at all possible, avoid full discharges and charge the battery more often between uses.
     
  17. scaesare

    scaesare Active Member

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    #17 scaesare, Dec 29, 2013
    Last edited: Dec 29, 2013
    You are implying that you could do (85kWh x 10%) x 4,700 = 39,950 discharge/charge cycles at 10%.

    What you are trying to describe isn't outlined in that article that I can see. Citation please?
     
  18. yobigd20

    yobigd20 Well-Known Member

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    I don't need to cite anything since that's how it's described in the article. A full discharge cycle is from 100% to 0%. Therefore if you only do 10% depths of discharge your battery could last up to 4700 of these full cycles.
     
  19. ElSupreme

    ElSupreme Model S 03182

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    yobigd20 is reading the chart correctly. You get an order of magnitude of battery life increase with much shallower DoD.

    In the paragraph preceding your table:
     
  20. scaesare

    scaesare Active Member

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    I don't see anything that states an "order of magnitude" (i.e. a 10X improvement) longer life, given the same amount of total energy usage, which is what yogibd20 is implying above.

    For the same amount of driven miles, if you only discharge to half your planned energy usage, an then recharge, you will double your number of charging cycles. Provided you don't hit the extremes of the battery limits, none o fthe curves I've seen suggest what you say.

    Here's another example: Battery Life Article. The curve is not for Li-ion, but notice the text describing it:

    "The above graph was constructed for a Lead acid battery, but with different scaling factors, it is typical for all cell chemistries including Lithium-ion. This is because battery life depends on the total energy throughput that the active chemicals can tolerate. Ignoring other ageing effects, the total energy throughput is fixed so that one cycle of 100% DOD is roughly equivalent to 2 cycles at 50% DOD and 10 cycles at 10% DOD and 100 cycles at 1% DOD"

    This is the reason why I'm asking for a citation. Everything I've read agrees that shallower is better for Li-ion, but also suggests that discharge cycling at a fast rate is a reciprocal factor.


    All other things being equal, shallower is better. What I'm arguing is that there's any real benefit (much less the 10x being claimed) for plugging in a bunch of times during the day as long as you don't hit extremes.
     

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