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Has anyone seen a TM "Ideal Charging Protocol?"

Discussion in 'Model S: Battery & Charging' started by RicH, Jan 8, 2014.

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  1. RicH

    RicH Member

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    I have been unable to get a consistent answer from service or sales on the BEST protocol for regularly charging my MS. Tesla has said we should set the "normal" charge for what we use on a regular basis. They did NOT say we should keep it at the "old" standard of 90%. I have been told that the NUMBER OF CYCLES is irrelevant, so charging, even a little, every day is fine. :confused:

    However, many of us (including me) have seen drops of 10-15% charge capacity with a year or 12k miles. I would really like to have an FAQ from TM engineers as to their current opinion on the way to maintain optimal condition/charge capacity. Has anyone seen such a post/comment? If TM is monitoring this forum, please advise. Love the car and want to maintain it.
     
  2. yobigd20

    yobigd20 Well-Known Member

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    just because the rated range is showing a lower number doesn't mean there's been ANY battery degredation whatsoever. In addition to them constantly changing and optimizing the algorithm and keeping a reserve amount, the battery cell's won't always be perfectly balanced like they were day 1 when you got the car, AND on top of all of that, unless you are repeatly depetling your battery to completely 0, and by 0 I do not mean 0 rated range, I mean 0 state of charge , and then once there then fully charging to 100% - the SOC will never be 100% accurate (and this is impossible for us to do due to the reserve amount, nor is it recommended to do 100% depth of discharges). Such is the nature of lithium ion batteries.

    So again this doesn't mean you've seen any degredation at all. I'll see the rated range number jump up and down for the slider % all the time, and I'll see jumps up several miles, the next down a few, and keep slowly going down, then after a month or two it'll jump up 8/9 miles, it's all over the place. Again, I seriously doubt anyone at all has seen any significant amount of real degredation. Only time will tell.

    As far as charging guidelines, you can grep these forums for LOTS of threads on this, but the gist of it is (without going into detail), charge as frequency as you can and keep the depth of discharges as minimal as possible and always stay within 30-70% if you can. It's not bad at all if you don't, but if you want your car to theoretically last FOREVER (like greater than your lifetime), then do whatever you can to keep that battery pack around 50%. I guess if you have a really short commute (like 2 miles), then the most ideal would be charge to 50-51%. go to work. get home. it's probably at 49%. and charge it back to 51%. again thats all theoricically in nature but I would think thats going to be best case scenario for this pack to last like 100+ years lol. For me, have a long commute. So I charge to 80%, get to work and its at 20%ish, charge back to 80% and then go home (20%), and charge back to 80% again. Always trying to "balance it" in such as way to keep me away from the bottom 20% and the top 20%. Thats best case for me right now. It'll be different for every person depending on their daily driving habits.
     
  3. rjcbox

    rjcbox Member

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    Thanks yobigd, helpful info. I think in a previous posts you said your commute is 100miles each direction? (driving fast on NJ turnpike) If so, is that discharge (80% to 20%) during winter driving? - i.e. these frigid days were now seeing in NJ
     
  4. Trnsl8r

    Trnsl8r Blue 85kwh since 12/8/12

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    Isn't this how you get your battery pack bricked?
     
  5. yobigd20

    yobigd20 Well-Known Member

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    yeah its around that. summer time my avg Wh/mi is around 350. But lately in this frigid weather, its about 400-450Wh/mi. For the last few days I've been timing my charges to complete 90% right before I leave (again, *timing* it, I don't stick it at 90% at full amp charge and leave it sit there overnight, trying to keep being at >80% to a minimal, and as a side effect of this my battery is warm as soon as I leave so I have full regen in this cold weather). But I have a P85 and a lead foot. Soo I'm sure others are getting better Wh/mi than me. This means starting at around 230 miles and when I get to work its about 70 miles left. Using like 150-160 rated range to go 100 miles due to my lead foot and cold weather. So I charge back up and repeat the same thing home.

    I guess one way to look at that is looking at the kW used during the summer vs now. During the summer I've seen it as low as 33kW to get to work (one direction). The other morning it was 51kW. Yesterday it was 54kW. This morning it was 45kW. Easy to do the math on that because it's exactly 100 miles to work. aka 330Wh/mi during summer, 510Wh/mi on Tues, 540Wh/mi yesterday, and 450Wh/mi this morning. Granted, the two > 500Wh/mi I was going REALLY fast. like REAALLLLY fast. 450Wh/mi was going with CC @ ~85mph Took a "slow" drive in this morning haha

    yes that's why I said 'nor is it recommended to do 100% depth of discharges'. They actually made it pretty hard to brick hte battery. They keep a reserve amount, 5kW or something like that, and goes into a deep sleep kinda thing to turn everything off to prevent bricking. So to reiterate, *dont* deplete your battery to 0 rated range (or < 0 rated range) on purpose just for the sake of trying to improve the rated range calculation. If you have a long road trip or something if you barely make it there with 1 or 0 miles remaining, that's fine.
     
  6. 100thMonkey

    100thMonkey Member

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    my understanding is that zero rated miles is a long way from bricking, which comes from running it down to zero and then leaving it that way long enough, probably at least days, unplugged so the floating voltage drops so low that the chips on each battery cell no longer function enough to accept a charge upon plugging in (I think I have that correct).

    I have no reservations about running the car down to zero or even till it won't go any further if I really need to as long as I know I can plug it in right away. I also accelerate with less and less intensity as the pack gets down to zero, it's my understanding that the resistance at low SOC can lead to heating, but then again, Tesla's BMS limits draw at that point anyway, so it's probably overkill.
     
  7. Zextraterrestrial

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    and then all you need to do is freeze the cells and smack them really hard to remove the lithium plating ...and charge back up:wink:
    I've heard it works for some batteries, no guarantee though
     
  8. jerry33

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

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    Might take a while to go through them all :)
     
  9. rjcbox

    rjcbox Member

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    Appreciate all the details and great info describing how Model S performs in extremes of winter temps, long commutes (and warp speeds lol)

     
  10. dave

    dave Member

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    For what its worth, I disagree with Yobig, and believe many of us are experiencing degradation in our batteries. I am in the minority though and get chased out of town, so I generally keep quiet. Much of the wisdom on this topic is derived from people forming opinions and reinforcing it with each other to the point that it becomes almost an accepted truth. The reality is that Tesla has not given us guidance or much information on the topic, which is quite frustrating. All we know is that they reduced the standard charge from 93% to 90% and then gave us a slider so we can charge to much lower percentages. All of this implies that keeping a lower state of charge is better for the battery (consistent with conventional battery management technique) but I haven't seen any hard data from Tesla on expected degradation rates, what is "normal", preferred charging rates, etc. I suspect it may partially be because they truly don't know what to expect exactly since everything is so new. I also think it's because they want to keep it simple for the masses and therefore aren't releasing too much technical info. If they come out and say that the optimum charge percentage is 65%, that not going to go over well with new buyers who just want to keep her full and not think about it.
     
  11. gaswalla

    gaswalla P4201/85/airsusp/pano/19i

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    yes, there is some degradation going on.. it' s not all just "balancing" or "software issues".. it's a combo of all three factors.
    my observation is that it seems to be tied into chronological life of the battery even more so than miles driven (based of folks that have had the car for >1 year having range charges of 240-250 miles regardless of miles driven).. my opinion
     
  12. Benjamin Brooks

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    Agreed Dave. There is degradation within the first year (where the majority of owners stand), and I'm sure it varies a fair amount per battery pack, and I'm sure it's nearly impossible to nail down how much it really is at any given point (perhaps within 5-10 "miles" of certainty).
     
  13. jerry33

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

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    Of course, the slider hypothesis is muddied because of the EPA testing rules. With a slider they can only rate on a full charge rather than averaging two fixed points.

    Also there is a fair amount of data on how Roadster batteries perform. It's thought that the Model S batteries will perform no worse than Roadster batteries and may perform significantly better.
     
  14. thefortunes

    thefortunes Member

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    When I spoke with a Tesla engineer last year about my specific situation (Roadster with a long commute and can plug in at 110 at work) he stated that I should plug in whenever available, and that there was not a statistically significant difference in keeping the battery lower than the 85% standard it charges to. However he did state that many small charges are better than the equivalent deeper discharge and longer charge.

    For what it is worth, here http://www.pluginamerica.org/surveys/batteries/tesla-roadster/PIA-Roadster-Battery-Study.pdf is the reference for the Roadster data that Jerry33 referenced above.

    The conclusion derived was:

    Of the factors considered – miles driven, vehicle age, and climate – only mileage showed a significant correlation with battery pack capacity.

    Data collected suggests that, on average, a Roadster battery pack will have between 80%
    and 85% of original capacity after 100,000 miles.

    Unlike results from the Plug In America LEAF Battery Survey5, no significant correlation was found between climate and battery longevity.

    There is significant variation in battery capacity reported; the difference in capacity between vehicles with similar mileage can be as large as the projected loss over 100,000 miles of use. Individual owners should therefore expect variation between their experience and the projected average performance.


    I have 22,700 miles on my Roadster and have 2%-3% degradation (depending on whether I use rated range or a measurement of amp-hour capacity that is available in the Roadster).

    My $0.02.
     
  15. AmpedRealtor

    AmpedRealtor Active Member

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    Optimum charge level, as confirmed with me by Ownership a few months ago, is in the 50%-60% range. Tesla stated that keeping the battery at that charge level would maximize long term battery life and minimize degradation over time. He stated that any benefit seen at this level would be "negligible", but would not quantify what he meant. Since then I have been keeping my battery at 50%, charging to higher level only before leaving. I have a full power HPWC, so it doesn't take long for me to charge up. This method has been working well for me. I have no concerns whatsoever about battery degradation, as I never run the car below 20% charge and never go above 80% charge, most of the time the car sits at 50%-60% charge unless I need to go across town.
     

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