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Is it okay to only fast charge?

Discussion in 'Model S: Battery & Charging' started by beingpaulp, Apr 26, 2015.

  1. beingpaulp

    beingpaulp Member

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    Hi all, so I picked up my Model S about 1 month ago. I had it in for some service last week and the guy at the service center told me just as I was leaving:

    "You don't want to supercharge your car all the time. It's really meant only for long trips. Supercharging all the time will degrade your battery"

    I suspect they logged all my trips to the supercharger (I only charge at the factory or using my chademo adaptor) and maybe they noticed how often I've fast charged.

    So here's my issue... before I knew that I went ahead and got 3-phase (480V) power at my home (at somewhat great expense) and the only reason I got the chademo adaptor was so I could use it with a chademo station at home.

    There is a good reason for this, I live up a mountain. It takes about 20% of the battery capacity to get from the bottom of the mountain to my home (3k ft elevation). On top of that, I have a 100 mile/day commute. Sometimes when I get home, I have to leave in only a few hours. I want to charge fast!

    I've read a few posts on the net, and the general consensus is that in a Nissan Leaf, fast charging *does* degrade the battery, but it doesn't seem like the Model S is affected. It makes sense to me coming from the RC world where you want to stay within LiPo battery "C" ratings. The larger pack should be able to safely charge at a higher rate. The Leaf is 24kWh, and the MS is 85kWh, this explains why the Supercharger can safely charge at the high rate.

    What do you guys think? Should I abandon my plans for chademo at home and just go with 10kW or 20kW (dual) home charging like everyone else? or will I be fine with a ~50kW chademo charger for home use?
     
  2. David_Cary

    David_Cary Member

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    Personally, I think it is as simple as heat causing degradation. I might be wrong of course. The amount of heat from a Chademo charge into an 85 isn't bad and of course, Tesla can cool if needed.

    The biggest issue to me would be the cost. 20kw is pretty fast. Few hours = full battery or at least over 80 which would allow you to be nearly full at the bottom of the mountain.
     
  3. jerry33

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

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    I wouldn't Supercharger to 100% for every charge, but a daily charge shouldn't be a problem as the cooling will keep the battery at a safe temperature, and I believe the charge rate will slow down if it can't cool fast enough (e.g. Arizona). Of course, you could manually dial it down by five or ten amps to start with if the ambient temperature is very high.

    Also SC personnel have been known to give conflicting and sometimes outdated information. The only "official" communication I've seen is that there is no harm in Supercharging. CHAdeMO doesn't charge as fast as a Supercharger, so there shouldn't ever be a problem there.
     
  4. Patrick W

    Patrick W Member

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    You might want to have a look at Supercharger Etiquette .

    It's a thread I started a couple of days ago about Etiquette for newbies about supercharger use but it's sort of evolved into a discussion about whether constant high speed charging is good or not.

    FYI, at this point I'm not sure which side I'm on. Both sides have their supporters and detractors. With my S due to arrive in the next few days (and with a supercharger near my house) I guess I'm going to have to decide soon.

    - - - Updated - - -

    I'm hearing that while one can set the percentage of charge at superchargers, superchargers ignore the amps setting.
     
  5. Barry

    Barry Member

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    While I have no real word knowledge about it, the engineer in me thinks that the additional heat generated by a 150A charge will accelerate battery degradation (despite the car's battery cooling capabilities).
     
  6. SabrToothSqrl

    SabrToothSqrl Active Member

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    It's covered by a 8 year unlimited mile warranty... charge away...
     
  7. jbcarioca

    jbcarioca Active Member

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    There is a good deal of conventional wisdom regarding battery charging that seems to date from the early days of li-ion and especially related also to very large cells (B787 the stellar example). I am no expert and make no claims that I am correct, however:

    I did sit through the entire NTSB li-ion sessions following the B787 fires and heard Tesla battery engineers on several subjects, including charging protocols.

    My understanding from all that is that specific chemistry, production quality control, deployment design, connection design, cooling, charging balancing and a few other factors are important. Much of the discussions on this subject seem to be based on generic designs rather than Tesla-specific situations. Based on my review of notes during those sessions and a few other data sources my opinion is:

    1. Limitations in Tesla applications are far less serious than are those of most other li-ion applications;
    2. Tesla battery pack design is vastly different (NOT hyperbole) than most other applications;
    3. Within tesla there are numerous overcharge, undercharge, overheat and freezing protections than any other applications;
    4. The common cell by cell variations in li-ion deployment are largely mitigated by very rigid and comprehensive Tesla quality control, including testing of every cell at production, reinstallation and after installation. At the time of testimony nobody else apparently did all that, including Boeing and automotive users.
    5. Among the most important factors is charge and discharge load balancing, where Tesla has a significant lead over all other li-ion users (or did at the time of NTSB testimony);
    6. The last point explains why Tesla (Model S and new-battery Roadster at least) can accept very fast charging without harm.

    Final point: The traditional li-ion problem point has been thermal runaway, typically caused by overcharging, which in turn causes overheating. "Ain't gonna happen" with your Model S.

    Net: Supercharge away! However, try to make a habit of staying between 20% and 85% or so. That is probably "belt and suspenders" logic given all the safeguards built in to Tesla applications. However, it does no harm and may extend battery life. tesla warranty says nothing about the subject. Were it critical, they surely would make specific guidance.
     
  8. arg

    arg Member

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    Leaving aside the general question of whether Supercharging regularly is a problem, your situation is rather better than that:

    - You are only talking CHAdeMO, not full Supercharge - only about a third the rate (note that you never get 50kW out of a "50kW" CHAdeMO - best you'll ever get is 48kW, and when the battery is empty 45kW, and that assumes you buy the highest-rated CHAdeMO kit available).

    - Living on top of your mountain, there's never any point charging to 100% full at home (presumably you recover a fair bit from regen on the way down).

    So, if money's no object, by all means get the CHAdeMO; it's probably harmless, and even then you don't have to use it every time, since 40kW overnight will probably do the trick most days.

    OTOH, I really wonder whether it's value for money in your situation, compared to dual chargers and 80A - 80A will put back your commute in about 90 minutes, so how often do you really come home and turn around within 90 minutes for a long drive?

    Also, if your situation is really as extreme as it sounds, the place you really want the CHAdeMO unit is at the foot of the mountain! Assuming that's not practical,. maybe spending some of the money saved on not having CHAdeMO at home would be better spent getting an HPWC put in with a friend or business at the foot of the mountain to fix the case when you arrive there without enough charge to get to the top - which could be a more common situation than needing the fast turn-around.
     
  9. bob_p

    bob_p Member

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    Charging using the HPWC, J1772 or chademo adapters use the on-board single or dual chargers. With my HPWC at 80A, I get around 60 miles of range per hour. And have been charging at that rate for most of the over 2 years I've had my P85, without any noticeable difference in range.

    Supercharging is different - it bypasses the on-board chargers, and charges at a much higher rate, tapering charge as the battery nears full capacity, to protect the battery.

    There may be some risk in charging frequently to more than 90% capacity, especially if the car sits with higher battery charge for a while.

    Other than charging to more than 90% - there shouldn't be any issues with using any of the adapters that use the on-board chargers.
     
  10. tga

    tga Active Member

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    Which does not cover degradation...
     
  11. mmccord

    mmccord Member

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    My understanding was that chademo is direct DC charging also (bypassing the on-board chargers). Is that incorrect?
     
  12. gavine

    gavine Petrol Head turned EV Enthusiast

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    I wasn't aware that the chademo uses the onboard charger. I thought it was a DC charge and bypassed the charger. Otherwise, how do you get more than 20kWh with chademo?
     
  13. tga

    tga Active Member

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    Incorrect. CHAdeMO, like Supercharging, bypasses the on board chargers and feeds the battery directly. Essentially a lower-powered supercharger. All L3 DCFC standards (CHAdeMO, CCS, Superchargers) work this way, on all cars.

    Your understanding is correct.
     
  14. Cottonwood

    Cottonwood Roadster#433, Model S#S37

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    More power is always better for quick charging.

    My opinion is that I would not worry about regular quick charging, but on the other hand, a personal CHAdeMO is probably more than you need.

    Let's look at your numbers. 20% of the battery is about 50 rated miles. 3,000 feet up is about 18 rated miles. That means your drive home is about 32 rated miles distance and 18 rated miles for altitude. If you leave some room in the SoC for regen, you will probably get most of those 18 altitude, rated miles back driving down the hill; that is a big win. Next, with a 100 mile per day commute, it's pretty easy to do your daily charge to 80 or 90% and still have a 100 rated mile buffer when you get home. Lastly, a solid 240-Volt, 80 Amp (dual chargers and HPWC) will give you almost 60 mph charge rate. That should work pretty well.

    480 Volt, 3-phase is very impressive for a home!

    BTW, if your 3-phase system only gives you 208 Volts, you can install a boost transformer of a few k$ to boost 208 up to 240, or a buck transformer to get 240 from 277.

    Finally, I am looking at getting a CHAdeMO installed at a local community center. What CHAdeMO did you choose and why?
     
  15. LucM

    LucM Member

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    What is covered by the warranty exactly? Is a 20% degradation covered? I don't think so.
     
  16. beingpaulp

    beingpaulp Member

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    Thanks for the replies everyone!

    Its true that chademo is DC charging (bypassing the on-board charger, similar to Supercharging) I partly justified the costs of the $500 chademo adaptor by saying I wouldn't need the dual chargers, or a HPWC.

    The mountain I go up is really steep, the 3k feet climb is only a 3-4 mile trip. I do regen about 3% going back down, so I never charge to 100%, so far I've only charged to 85% at home. Sometimes on a Saturday or Sunday, I might make the trip up and down 4 times! There is a public L2 (chargepoint) station just before going up that I can use if needed. So far, I've been pretty good at trip planning and either swing by Fremont on my way, or some other public chademo station so I make sure I get home with at least 10% to spare.

    I haven't actually looked into the chademo station yet, there is a diy style unit from Electric Motor Werks, Inc. - Home or I might try contacting ABB to buy their unit.

    Getting 3-phase power wasn't as hard as I thought, the power company actually delivers power up the mountain as 3-phase and typically would put a transformer on the pole before running the lines to your home. In my case I have no transformer.

    I'll keep an eye on my battery degradation, and report back if it looks worse than expected.
     
  17. yobigd20

    yobigd20 Well-Known Member

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    the negatives of fast charging is negated by tesla's battery thermnal management system. supercharging will not degrade the batteries as they are temperature controlled staying within safe ranges. the only thing that you can do to hurt the battery is fully deep cycle it often. (100%-0%-100%-0%) or leave it sitting for a long time fully charged at 100% or completely empty at 0%.
     
  18. scottm

    scottm Active Member

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    Charging at higher power is more energy efficient.

    Put in the CHAdeMO and put it on sharepoint you could save the day for some EV travellers passing by.

    Or, are you at the end of a private road?
     
  19. taurusking

    taurusking Member

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    What drives me crazy is that most of the information I received was through discussion with fellow MS owners.

    I wish Tesla gives a concrete handbook of charging at the time of delivery.

    Things like do not charge to 100% all the time and let the car sit at 100% charge without being driven should be in RED pamplet of some kind.
     
  20. gavine

    gavine Petrol Head turned EV Enthusiast

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    Some say those ill-affects are so minimal with Tesla's battery chemistry that it's not worth worrying about, which is probably why they don't say anything. I think thermal management is the most important thing and Tesla's system mitigates it.
     

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