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

Charge loss

Discussion in 'Model S: Battery & Charging' started by StephRob, Jul 2, 2012.

  1. StephRob

    StephRob Member

    Joined:
    Jan 26, 2012
    Messages:
    210
    Location:
    Kentfield CA
    This has probably been discussed at length somewhere here, but I searched and can't find it, so please feel free to direct me. What is the charge loss after you fully charge the battery if the car then sits unplugged for a while? For example, what if I arrive at the airport with my 85KwH battery at a 95% charge and leave it in the airport garage for two weeks? (Not connected to a charge station of course) Or even just overnight? What is the loss of charge from a Model S just sitting idle?

    I know all about the bricking issue (or lack thereof an issue) and found this in a Tesla blog: a Model S battery parked with 50 percent charge would approach full discharge only after about 12 months. Model S batteries also have the ability to protect themselves as they approach very low charge levels by going into a “deep sleep” mode that lowers the loss even further. A Model S will not allow its battery to fall below about 5 percent charge. At that point the car can still sit for many months.

    But my question is at the other end of the charge spectrum - loss from a full, or nearly full, charge. Thank you!
     
  2. jerry33

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

    Joined:
    Mar 8, 2012
    Messages:
    12,766
    Location:
    Texas
    The thread you want is here. You don't want to leave the Tesla parked with a full charge. That's about the worst thing you can do to the battery that doesn't involve a sledge hammer.
     
  3. StephRob

    StephRob Member

    Joined:
    Jan 26, 2012
    Messages:
    210
    Location:
    Kentfield CA
    Thank you Jerry. I did read through that thread and it deals mostly with extreme temperature effects. What if I leave it unplugged in my 65 degree garage? Is that awful (i.e. the worst thing that doesn't involve a sledge hammer)? :)

    I guess another way to approach this is: How much power will the car consume (assume 85KwH battery) if I leave it plugged in and don't drive it? It will be fully charged in the first few hours, but how much energy will be consumed each day to maintain this charge? Assume a very normal temperature range (50-70 degrees)
     
  4. kevincwelch

    kevincwelch Active Member

    Joined:
    May 13, 2012
    Messages:
    2,018
    Location:
    Chicagoland
    I have to admit that I read through that thread and tried to digest it. Exactly how is this bad? How would this be different from unplugging the Model S, driving 10 miles (minimal discharge) and leaving it unplugged for my 12 hour day at work?
     
  5. dsm363

    dsm363 Roadster + Sig Model S

    Joined:
    May 17, 2009
    Messages:
    18,235
    Location:
    Las Vegas, NV
    #5 dsm363, Jul 2, 2012
    Last edited: Jul 2, 2012
    The car will take care of its battery pack and the thermal management on its own. Leaving it unplugged for a while at a full standard charge shouldn't be horrible on the battery so I wouldn't worry about it. If it's in your garage, I'd leave it plugged in but if your forget now and then it is not a big deal. If you leave it plugged in and don't drive it, that's also not a big deal. I assume you'll charge in standard mode usually so it's actually not a full charge anyway. Not sure exactly how much charge it uses up sitting there each day.
     
  6. brianman

    brianman Burrito Founder

    Joined:
    Nov 10, 2011
    Messages:
    15,487
    "shouldn't"?
     
  7. dsm363

    dsm363 Roadster + Sig Model S

    Joined:
    May 17, 2009
    Messages:
    18,235
    Location:
    Las Vegas, NV
    Yes. Sorry, shouldn't be hard on the battery is what I mean to type. Thanks.
     
  8. jerry33

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

    Joined:
    Mar 8, 2012
    Messages:
    12,766
    Location:
    Texas
    I was referring to a full charge e.g. range charge. I should have made that clearer. Plugging it in daily for a standard charge is the correct thing to do.

    If the battery uses 2 kWh/day in extreme temperatures, it's going to be less in moderate temperatures. Until a few people actually get their hands on a Model S and post the numbers here, it's mostly speculation based on experience with the Roadster.
     
  9. kevincwelch

    kevincwelch Active Member

    Joined:
    May 13, 2012
    Messages:
    2,018
    Location:
    Chicagoland
    Thanks, Jerry

    Sent from my Nexus S 4G using Tapatalk 2
     
  10. brianman

    brianman Burrito Founder

    Joined:
    Nov 10, 2011
    Messages:
    15,487
    @jerry33 - I thought that's what you meant.

    To make sure my understanding is correct on the other end of the spectrum...

    Scenario A
    Charge to 80% SOC
    Unplug
    Wait until 15% SOC
    Plug back in

    Scenario B
    Charge to 70% SOC
    Unplug
    Wait until 5% SOC
    Plug back in

    Scenario B is more detrimental to the battery's longevity as well. Correct?

    Edit: Removed "range charge" to avoid confusion, hopefully.
     
  11. dsm363

    dsm363 Roadster + Sig Model S

    Joined:
    May 17, 2009
    Messages:
    18,235
    Location:
    Las Vegas, NV
    Range charge is a bugger charge so 100% of battery that Tesla gives you access to.
     
  12. stopcrazypp

    stopcrazypp Well-Known Member

    Joined:
    Dec 8, 2007
    Messages:
    7,056
    AFAIK, the lower end is not detrimental to battery longevity, but it does leave you with very little range left, less battery power (because of lower voltage) and higher risk of under-voltage/bricking. The situation is similar for low temperatures (there is less apparent capacity/power during operation, but no real battery longevity affects).

    The reason to minimize the time spent in high SOC is because it promotes oxidation (same with high temperatures), which means quicker degradation of the battery cell. That's why storage mode in the Roadster is 50% SOC.

    According to Wikipedia, a laptop cell stored at 100% SOC loses 20% capacity in a year at 25 degrees C. Stored at 40-60%, that reduces five-fold to 4%/year.
    Supposedly some chemistries like LiFePO4 are not affected by being stored at high SOC.
    Lithium-ion battery - Wikipedia, the free encyclopedia
     
  13. StephRob

    StephRob Member

    Joined:
    Jan 26, 2012
    Messages:
    210
    Location:
    Kentfield CA
    I started this thread because someone my husband was talking to said that EVs constantly lose charge and waste electricity. So when they are plugged in they are wasting energy. Sort of like a dripping faucet, or a "vampire" appliance. I realize this is much less important than these issues of battery health and "bricking" and so forth, but I'd love to know the facts on this issue in order to respond to this criticism.
     
  14. dsm363

    dsm363 Roadster + Sig Model S

    Joined:
    May 17, 2009
    Messages:
    18,235
    Location:
    Las Vegas, NV
    The car will use a small amount of energy if it's plugged in or not plugged in just with battery management so that amount is the same. The fact that it's plugged in has nothing to do with wasting energy as this guy put it. It uses more energy of course when you start charging. My Roadster might use 1 kWh over a day of just sitting there so about 7 cents worth of electricity. This guy wastes that driving his ICE a few hundred yards.
     
  15. StephRob

    StephRob Member

    Joined:
    Jan 26, 2012
    Messages:
    210
    Location:
    Kentfield CA
    That is very helpful. Thank you!
     
  16. stopcrazypp

    stopcrazypp Well-Known Member

    Joined:
    Dec 8, 2007
    Messages:
    7,056
    #16 stopcrazypp, Jul 3, 2012
    Last edited: Jul 3, 2012
    Like dsm636 says, the Model S will draw a small amount of power whether it is plugged in or not (for subsystems, some EVs like the Leaf don't draw any power when "off"). This number is reduced compared to the Roadster. From Tesla's blog, a Model S at 50% SOC would take ~12 months to approach full discharge. 50% of 85kWh = 42.5kWh. Divide this by 365 days and you get 0.116kWh per day on average (or about a 5W draw).

    For the Roadster (56kWh), it takes more than 2 months from 50% SOC. 50%*56kWh/60 days = 0.467kWh per day (or about 19.5W draw).

    Keep in mind if your ICE car has an alarm system, it also continuously draws power. Given it takes a WHOLE YEAR to drain half a charge, I think it's a non-issue overall.
    Plug It In | Blog | Tesla Motors
     
  17. dsm363

    dsm363 Roadster + Sig Model S

    Joined:
    May 17, 2009
    Messages:
    18,235
    Location:
    Las Vegas, NV
    No problem. I don't know the exact amount of energy so that number was a guess. Just from looking at my Roadster, whatever energy usage it is (even sitting in Texas summer outside and unplugged) is so small, I don't even notice it or even think about it when I get back into the car.

    Much better analysis from stopcrazypp. I might have even guessed high. Either way, don't think it's really something to worry about.
     
  18. jerry33

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

    Joined:
    Mar 8, 2012
    Messages:
    12,766
    Location:
    Texas
    Depends on if you're driving it or storing it. If you're driving it, both are wrong. If you're storing it the differences between the two methods will be negligible. Charging to over 90% and then letting it sit is harmful.

    hcsharp has written the best explanation that I've seen:

     
  19. jerry33

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

    Joined:
    Mar 8, 2012
    Messages:
    12,766
    Location:
    Texas
    Note that every modern car uses some power when turned off. In an ICE car, the battery isn't the primary motive source, so the battery doesn't have to be as big. Examples of what ICE cars run when the car is off are:

    Security system
    Engine fan
    Light relay(s) -- In cars that turn the lights off when you open the driver's door a relay keeps the circuit open
    Brake pump*
    Water pump(s)*
    Cabin cooling fan
    Telemetry

    The only thing an EV adds to the picture is battery thermal management. At the 2 kWh that's been bandied about for extreme temperatures that's 18 cents where I live. 18 cents will go about 4 commuting miles in my 2004 Prius (($0.18/$3.20)*73). Most cars won't go anywhere near that far.

    *If these are electrically powered
     
  20. gg_got_a_tesla

    gg_got_a_tesla Model S: VIN P65513, Model 3 Res Holder

    Joined:
    Jan 29, 2010
    Messages:
    6,097
    Location:
    Redwood Shores, CA
    I've had an ICE battery die on me when the car was parked for about 3 months without being driven, ostensibly due to the alarm system. If anything, such a scenario would not be an issue with the Model S!
     

Share This Page