TMC is an independent, primarily volunteer organization that relies on ad revenue to cover its operating costs. Please consider whitelisting TMC on your ad blocker or making a Paypal contribution here: paypal.me/SupportTMC

Definitive pack rebalance technique?

Discussion in 'Model S: Battery & Charging' started by spaghetti, Mar 10, 2014.

  1. spaghetti

    spaghetti Member

    Joined:
    May 10, 2013
    Messages:
    245
    Location:
    Silicon Valley
    #1 spaghetti, Mar 10, 2014
    Last edited: Mar 10, 2014
    There has been much discussion about pack balancing, loss of range, etc, but I can't seem to find a definitive approach to rebalancing the battery pack. Can some of the experts on this forum please post a summary of the best approach to rebalance? Perhaps the mods can make it a sticky. Thanks in advance.
     
  2. djp

    djp Roadster 2.0 VIN939

    Joined:
    Aug 28, 2011
    Messages:
    1,108
    Location:
    Toronto, Canada
    We don't have official information from Tesla on balancing, so the best we can do is use experience from the Roadster, information from service techs (which is sometimes conflicting) and feedback on what has worked from other owners.

    There are two factors at play:

    1. Calibration of the algorithm that estimates battery pack capacity (CAC, or calculated amp hour capacity). On the Roadster the capacity is recalculated when by doing a single drive (single key turn) from >85% SOC to <20% SOC and then recharging in Standard mode. We don't know what triggers a capacity measurement in the Model S, but as a starting point we can assume it's the same as the Roadster (and this seems to agree with advice given by service techs).

    2. Pack balancing. On the Roadster this done directly after a Standard or Range charge completes, but is faster and more effective after a Range charge. The length of time it takes depends on how far out of balance the pack is.

    So the basic procedure for balancing and recalibration of your pack is:

    1. Charge in Range mode and let sit for a few hours or overnight.

    2. Drive to less than 20% SOC on a single key turn.

    3. Charge back to 90%.

    4. Repeat until the range estimate stops rising.

    Note that letting your battery sit at 100% and doing deep cycles shortens long term battery life. It's best to combine balancing/recalibration with long road trips when you actually need the full range rather than doing unnecessary balancing just to get a higher number displayed on your screen.
     
  3. glhs272

    glhs272 Unnamed plug faced villian

    Joined:
    Aug 21, 2013
    Messages:
    791
    Location:
    Burlington, WI
    ^^^^This. Enough said.
     
  4. stopcrazypp

    stopcrazypp Well-Known Member

    Joined:
    Dec 8, 2007
    Messages:
    7,050
    Here's someone describing a successful balance on a Model S (firmware 4.4):
    It does not require you to drive down to lower SOCs (that's only necessary to "re-calibrate" your pack, not necessary to balance it). However, unlike the Roadster, it does require you to charge to 100% and leave it there for a while.
     
  5. eepic

    eepic Member

    Joined:
    Nov 6, 2013
    Messages:
    854
    Location:
    Canada
    As added tips:

    - Don't do this if you will not be using up the 'range charge' energy relatively soon afterwards.
    - Avoid doing this if the ambient temperature is super hot.

    Tesla has the best underlying battery chemistry to protect against this relative to other EVs and excellent active cooling (not sure it fully negates the second point), but I imagine it still has a minor impact on longevity. Battery life degradation happens as a function of time spent near its upper charge voltage specs, with it being worse at higher temperatures.

    Note: feel free to correct me if I'm wrong, this is all educated conjecture on my part based on
    https://www.youtube.com/watch?v=pxP0Cu00sZs
     
  6. VolkerP

    VolkerP EU Model S P-37

    Joined:
    Jul 6, 2011
    Messages:
    2,455
    Location:
    Germany
    Why would I want to restore the (displayed) range of the car, using range charging, if I don't plan to drive that range?
    out of curiosity. Understandable, but I'll try to help myself with that.
    want to sell the car. OK, but perhaps contact the buyer if it is OK with him to add degradation to the pack.
     
  7. Gizmotoy

    Gizmotoy Active Member

    Joined:
    Sep 16, 2013
    Messages:
    3,144
    Location:
    Bay Area, CA
    If the pack is unbalanced, it's real loss, not displayed (fake) loss. Rebalancing will restore actual range.

    But, yes, that should be weighed against the degradation you're causing. Short-term gains vs. potential long-term losses.

    The problem, though is that there's no definitive way for owners to tell some kind of algorithmic shortcoming vs. the pack legitimately being imbalanced. If you're just training the algorithm by following this process, you are simply fixing the displayed (fake) loss AND causing long-term degradation. Obviously you don't want to be doing that.
     
  8. Odenator

    Odenator P2607

    Joined:
    May 2, 2011
    Messages:
    334
    Location:
    Olympia, WA
    Because balancing takes time. It took me 4 months to get back 33 rated miles, and I need every one of them on the weekends.
     
  9. Chris Naps

    Chris Naps Member

    Joined:
    Jan 4, 2014
    Messages:
    183
    Location:
    New Jersey
    I've also been told to change it to run it down to 0% then charge to 100% and keep it there for three days to make sure it goes through calibration and rebalancing.
     
  10. VolkerP

    VolkerP EU Model S P-37

    Joined:
    Jul 6, 2011
    Messages:
    2,455
    Location:
    Germany
    That sounds like you do a range charge and a long drive every weekend. Basically you do as recommended in this thread to balance it.
    How can the pack become unbalanced at the first place, if operated like that? Perhaps did no letting it sit plugged in at a high SOC?

    * confused *
     
  11. qwk

    qwk Model S P2681

    Joined:
    Dec 19, 2008
    Messages:
    2,817
    "A" packs have different cells and firmware.
     
  12. nolngrgrsngslde

    Joined:
    Aug 14, 2012
    Messages:
    151
    Tesla tells you specifically to do neither of these two things, not 0%, and not 100%.

    The S battery balances automatically. I can buy a balancing charger for $40.00 to charge and autobalance an RC toy battery pack, why wouldn't Tesla's charger have the same thing.

    I also asked a Tesla tech and he told me that the S autobalances.
     
  13. stopcrazypp

    stopcrazypp Well-Known Member

    Joined:
    Dec 8, 2007
    Messages:
    7,050
    Then how do explain the numerous people that still have out of balance packs (which a proper balance has been confirm to fix)?

    Make no mistake, I'm not saying Tesla doesn't do a "maintenance" middle balance (which can be done at any SOC above ~50% assuming the car has an accurate voltage to SOC map), but such a balance is still less accurate than a true top balance (which charging to 100% will ensure). The reason why not to do this all the time is: 1) charging to 100% and keeping it there is not good for the battery 2) balancing wastes energy so if you don't need the extra range, no point in wasting the energy.

    For an RC toy and other consumer devices though, most users always charge to 100%.
     
  14. NigelM

    NigelM Recovering Member

    Joined:
    Apr 3, 2011
    Messages:
    13,257
    Location:
    Sarasota, FL

    ^^^ This.

    I've said many times that I've experienced minimal apparent degradation in both my Roadster (over 3years) and Model S (over 18 months) and all I do is plug both cars in every night and let them standard charge. I range charge maybe 3-4 times a year when I'm going on a long trip. I know plenty of others who do the same and have no complaints.

    In other words I follow Tesla's advice and I'm really happy. Personally I think Tesla made a mistake introducing the slider bar as that motivated folks to start guessing if a different charging pattern would work better. When anyone asks me I tell them to just plug in every night, doesn't matter if you drove 10 miles or 200 miles that day.
     
  15. ecarfan

    ecarfan Well-Known Member

    Joined:
    Sep 21, 2013
    Messages:
    10,375
    Location:
    San Mateo, CA
    #15 ecarfan, Mar 14, 2014
    Last edited: Mar 15, 2014
    There is a great deal of speculation by owners as to whether their pack is "out of balance" or not. It is pure speculation. Owners do not have access to the data necessary to definitively determine whether or not that is actually the case. The range mileage number is not enough information to make that determination.
     
  16. Mnlevin

    Mnlevin Member

    Joined:
    Feb 4, 2013
    Messages:
    417
    Location:
    South Florida

    I tried to watch the video but it was way too long, boring and technical, BUT that being said I did learn something from the bits and pieces I did understand. First that the battery can last a long time, if not forever if properly cared for. Second that charging SLOW does NOT improve anything. In fact from the stats presented charging slow is not good for the battery. Better to have it charge at the std 40 amp 240 volt, just dont leave it at a SOC without using it. So as Nigel has posted, we just basically charge the car at 240/40 each night to Std 85-90% and drive it each day. I do a range charge once in awhile, (maybe 1-2 times mo) when I am going to use the car a lot the next day (60-80% of capacity). So far in 20,000 miles I still have pretty much the same capacity 199 full and 174 std RR. Thinking about getting another Model S as my wife has pretty much taken the car during the week as she has a 50 mile daily commute and mine is only 8 miles unless I am out of the office on business when I am doing 100+ miles per day. Have never had an issue with the 60 so that will be the way to go for me. Also do 95% of my charging at home, but have used the PSL and PO Superchargers more than twice. Love the car and how it is holding up.
     
  17. bob_p

    bob_p Member

    Joined:
    Apr 5, 2012
    Messages:
    939
    We're all making one very large assumption - that the estimated range displayed after charging accurately measures how much battery charge is present across all of the batteries.

    What if that number is actually an estimate? Is the car actually able to measure the amount of charge in each of the 7000+ batteries?

    Or could it be that the number is an educated guess, based on the measurements the car can take - and then gets more accurate after the battery starts discharging?

    While there's been a lot of discussion on the potential range loss - can't recall seeing any discussion about how the range number is actually being calculated or how accurate it is.

    What I do see - is that when I first drive the car after charging - that the measured energy usage on the trip display is extremely large - and that it takes a while for that large number to be averaged out as the car is driven.
     
  18. tomas

    tomas Traded in 9 rep bars for M3, used to be somebody!

    Joined:
    Oct 22, 2012
    Messages:
    2,109
    Location:
    Chicago/Montecito
    ^^^Exactly. Also as stated by Nigel. There's been a frenzy about re-balancing, and fact is we really do not know. There are 5 possible things that could cause lower estimated (rated or ideal) range over time: 1) the estimating algorithm loses accuracy, 2) the estimating algorithm (or its inputs) change with software updates, 3) the estimating algorithm includes factors (such as outdoor temp averages), 4) the pack gets out of balance and therefore loses some charging capacity until rebalanced, and 5) the pack degrades (permanently loses capacity). Likewise, when you go through the recommended "rebalancing" exercises (i.e., range charge, running down to 20%) there are two things that could be happening: 1) rebalancing, and/or 2) estimating algorithm re-calibrates low and high capacity of pack.

    I've been reading all of the related threads for months with great interest. I know someone's going to claim authoritative knowledge and shout me down, but IN MY OPINION, NOBODY KNOWS EXACTLY WHAT IS HAPPENING.

    It would be nice if Tesla Motors would someday give us something authoritative, but I suspect that they view all of this as "within reasonable parameters", and have other more important fish to fry. PS, I do not view info passed from a Service Manager, Service Center technician, etc. as authoritative unless they can provide a Tesla letterhead TSB that shows it in writing. Bless those service guys, they're great, but they do not own the car, and therefore know less about day-to-day charging patterns than we do.
     
  19. AmpedRealtor

    AmpedRealtor Active Member

    Joined:
    Jun 30, 2013
    Messages:
    4,705
    Location:
    Buckeye, AZ
    To be fair, this is an assumption being made by owners. There has been no independent confirmation that this is the case. Just an assumption.

    There could very easily be other factors at play, or a problem with the algorithm.

    Agreed. The "balancing regimen" posted earlier does nothing more than teach the algorithm the endpoints of your battery's charge. This enables the algorithm to more accurately calculate your range estimate, which appears as "recovered" range. This is just as valid of an interpretation of what is happening as those who speculate about unbalanced battery packs. However, it's not recommended to charge to 100% if you don't need the range. Please, be careful about charging to 100%, then leaving it there, then running to 0% (dangerous). While it may look like you have "recovered" some range by following this procedure, you are also reducing the long term life of your pack.

    I do think Tesla needs to address this issue with some communication, but I would be surprised if it was real deterioration.
     
  20. Gizmotoy

    Gizmotoy Active Member

    Joined:
    Sep 16, 2013
    Messages:
    3,144
    Location:
    Bay Area, CA
    Right. Which is exactly what I went on to say in the next part of that comment, the part you removed here.

    It would be awfully nice to know which case you're in without trying to convince Tesla to tell you.
     

Share This Page