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I live at the top of a hill. Should I charge to less than 100%?

Discussion in 'Model S: Battery & Charging' started by GasDoc, Nov 22, 2012.

  1. GasDoc

    GasDoc Member

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    Getting ready to order my car and I have all kinds of questions.

    I live at the top of a hill. If the first thing I do everyday is coast downhill a mile and a half, can I charge to less than 100% so I can recapture all that potential energy?

    Seems like a waste to charge fully during the night and then go downhill.

    Will the car let me tell it when to stop after it gets to 90% or do I have to experiment with trial and error and figure out the optimal duration of time to charge so that I start out the day with less than a full charge but have regenerated enough to have a full charge at the bottom of the hill?
     
  2. dhrivnak

    dhrivnak Active Member

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    The car by default will only charge to about 90%. You have to speciffically tell the car to charge in range mode if you want the full 100%. And you typically do not want to charge all the time to 100% or you will degrade the battery. This works out quite well for me in the Roadster and yes you will be able to recapture your energy.
     
  3. Discoducky

    Discoducky Active Member

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    Standard charge should allow for regen down the hill, is my guess.
     
  4. dsm363

    dsm363 Roadster + Sig Model S

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    Hi,

    A standard charge only goes to 90% which is how you want to charge in a daily basis unless you need a full range charge. After a full range charge your regen is disabled or reduced initially so that shouldn't be an issue.
     
  5. bonnie

    bonnie Oil is for sissies.

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    As previous posters have said, charging in standard mode will give you 90% and leave plenty of room to recapture the downhill energy. (What a great way to start your day by putting miles IN to your car!).

    And while repeated range mode charges are not optimal for battery life, this is a different situation. Let's say you manage to complete fill that battery with electrons, same as you would with a range mode charge - you'll be using them immediately at the bottom of the hill, so the battery won't sit full. Seems like a win-win.
     
  6. GasDoc

    GasDoc Member

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    Hmmm...My work is right at the bottom of the hill, so I won't be burning any of the electrons I generated coasting to work.

    If it's bad for the battery to sit around at 100%, perhaps I should charge to 80% at home so that when I'm at work my car sits all day at 90%?

    I'm assuming the software will let me do this? Or do I have to figure out how much time to tell the car to charge for to approximate an 80% charge?
     
  7. jerry33

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

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    Charging to 70% or 80% should be fine depending upon how long the hill is. This will be easy to figure out once you get your car.

    Right now the software allows either a full charge or a range charge. However, you can set the rate of charge. The easiest way to do this is to set a very low amp charge so that it never reaches the normal 90% limit by the time you leave in the morning (you'll have to remember to change this setting on Friday for that long Saturday drive).
     
  8. dhrivnak

    dhrivnak Active Member

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    1.5 miles will NOT take you from 90% to 100%. I would not worry about it. If you had a 20 mile descend it may be a different issue but 1.5 miles is not a problem.
     
  9. bonnie

    bonnie Oil is for sissies.

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    Agree. I'd just charge in standard mode, pick up some miles going down the hill. The battery won't be full at the bottom of a 1.5 mile hill. Plus you're going to be looking for excuses to just drive. "Oh hey, I need to burn off some of the miles I picked up coming to work. Yep, whatcha gonna do??"
     
  10. GasDoc

    GasDoc Member

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    OK. I understand now. With the car default charging to 90%, I'll still be able to capture some of that potential energy going down the hill in the morning.

    I had the misconception that the car charged to "Full" and that I wouldn't regen going down the hill in the morning--I thought that would be a waste. Seems like I'll wake up at 90%, drive to work and end up there with 90%+. I'll be able to use some of that regenerated energy to go up the hill after work.
     
  11. brianman

    brianman Burrito Founder

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    Just to complete the picture...

    If you had a really long descent (say 50 miles), you'd have two problems: [1] you would max out regen and [2] you'd probably leave your car parked at work with 100% charge for the day which is generally bad for it.
     
  12. bonnie

    bonnie Oil is for sissies.

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    Really not a problem :) Just don't plug in when you get home at night & use the 50 miles of downhill to refill your battery.
     
  13. vfx

    vfx Well-Known Member

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    Or use the (coming) in car charge timer and set it to start at 4:00AM so you get an incomplete charge when you leave for work at 6:00AM (adjust times to your sched)
     
  14. strider

    strider Active Member

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    Hi GD. I live in the Belmont hills (92 and 280) and drive down the hill to 101 every day. You will not have to worry about overfilling the car on the way down. I actually don't "gain" any range dropping down, I just don't use any. So I leave my house w/ 181 miles (Roadster Standard charge) and when I get to 101 I still have 181 miles while having actually traveled about 4 miles. As others have said, do a standard mode 90% charge and you'll be fine. And you're right, you'll get to use that regen'd energy running back up the hill in the evening. No worries! :)
     
  15. richkae

    richkae VIN587

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    I also live at the top of a hill. I just went out and tested the steepest road off the hill. It is about 1.3 miles of 8-10% grade, ( the topo maps show about 500 foot elevation change )
    On the way down the hill I had my foot completely off the throttle for maximum regen almost the entire time ( about 25mph ), I didn't have to use the friction brakes until the stop light at the very bottom.
    Over that 1.3 miles I regenerated 0.5 kW, which is about 1.6 miles of range.
    Since a full range mode charge is about 30 miles more range than a full standard mode charge - I would probably need a road about 15-20 times that long to fill the battery if it already had a full standard mode charge.
     
  16. bonnie

    bonnie Oil is for sissies.

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    Nicely done, richkae.
     

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