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How to set scheduled charge to maximize saving?

Discussion in 'Model 3: Battery & Charging' started by ZooSean, May 13, 2018.

  1. ZooSean

    ZooSean ZOO

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    My power company charges me super low rates from 12am to 7am. And I have a J1772 charger which will do 32Amp max at my Garage to charge my Model 3 once it comes. I have seen in some video, Tesla can only set the starting charge time, but not end charging time. The maximum charge level could be set though.

    Whats the best way to set up , I don’t want the charging go beyond 7am, as it enteres the peak rate.

    I am also thinking install a Tesla HPWC which can draw 48amp out of it , so I don’t need worry charging over 7am.
     
  2. evJOULE

    evJOULE Member

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    ZooSean, you will likely get better advice from others here with actual experience in charging their Tesla, I'm still waiting for a VIN, but I would think that you could set the start charge time after 12am, and then either through trial and error, or by calculating the range added each hour for your particular setup, adjust the maximum charge level so that it can be reached before 7am. Enjoy your new ride when it comes.
     
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  3. swaltner

    swaltner Active Member

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    To run the calculations that @evJOULE describes. You have a 32 amp charger, which should be running at 240 Volts on residential service. That works out to 7.7 kW, call it 7.5 with a little bit lost to inefficiencies. A 7 hour charging window gives you the ability to draw 52.5 kWh per night. The battery on the Model 3 LR is apparently 80 kWh. That works out to 65% (52.5 kWh / 80 kWh). Set the car to start charging at midnight and stop at 65%. The only thing that would mess that up is if you had a power outage at midnight that delayed the start of charging if power is restored a little bit later.

    However, you're never going to arrive home at 0% charge, so if it's set to stop at 65%, your car will stop charging well before your 7 AM cutoff time. Personally, I would simply ignore the small chance of running into an issue and set your start timer to midnight, your max charge to 80% and be done with it.
     
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  4. ZooSean

    ZooSean ZOO

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    Thanks both for advice. Coming from a leaf world, this seems so complicated.
     
  5. SW2Fiddler

    SW2Fiddler your concern is noted

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    Yes, this!
    And in a few minutes after charging starts (admit it, you’ll stay up to watch!) an estimate will stabilize for time remaining. If it goes too long into your higher rate period, just bump the Max Charge down and watch it recalibrate charge time.
    If the difference is pennies, optimizing gets boring after a while. My power is actually free from 8PM to 6AM; I schedule charging for 8:05 and never give end time a moment’s thought. I want the charge level at 80%, even when that costs me one more buck (which is more than it ever does).
     
  6. azentropy

    azentropy Member

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    Do the S and the X have scheduled stop times or schedule windows? Didn't know if this is something that just hasn't made it to the Model 3 yet or that it didn't exist on any of them. Seems like something that would be very simple to add software wise.
     
  7. dhrivnak

    dhrivnak Active Member

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    As others say it will be rare when you need more than 52 KWh. That is 200+ miles in a day. For those few times just pay the extra. By the way the useable capacity on the 3 is just south of 75 KWh.
     
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  8. jsmay311

    jsmay311 Member

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    Tesla's lack of better scheduled charging options is really mind-boggling given how simple it would be to add in the software, and especially with more and more people having access to TOU plans nowadays.

    I hope this is something they remedy via OTA. But after 6 years of being behind the curve vs competitors with the S/X, it appears this is just not something Tesla cares about.
    Sad.
     
  9. animorph

    animorph Active Member

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    S & X are the same.

    TeslaFi has schedule controls to start and stop charging so that would be one way to ensure charging stops on time.
     
  10. ZooSean

    ZooSean ZOO

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    What’s TeslaFi?
     
  11. swaltner

    swaltner Active Member

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    :p

    Snarky (LetMeGoogleThatForYou.com) response:
    LMGTFY

    Less snarky response:
    Home -

    Possibly helpful response:
    It's a for-pay service that some Tesla owners sign up for that adds some automation tasks to Tesla vehicles. One of the big features it does is tracks individual charging and driving sessions and provides a summary to you of the use of your vehicle. The feature you would be interested in is the scheduling feature that lets you "Schedule commands to control your vehicle". The commands that you can schedule are listed at Scheduling - and include Start Charging and Stop Charging.
     
  12. TexasEV

    TexasEV Well-Known Member

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    In real life it’s not as complicated as some are thinking. If you set scheduled charging to start at midnight, plugged into a 14-50 outlet you’ll get 30 miles per hour of charge. So by 7am you’ll have added 210 miles. How often would you be adding more than that in a night? It will almost always shut off before then, as you’re not usually driving 210 miles in a day. If you are, you need the extra charge for an hour or two after 7 am even if it’s at a higher cost.
     
  13. AndreSF

    AndreSF Member

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    What he said ^ :) Chances are you will not need to worry about charging past 7AM, but if there are few of those occasions, you can set your charge level a bit lower potentially to make sure you don't charge past the end of low nightly rate.
    But if you want 100% guarantee, there are EVSEs out there with scheduling feature (start/stop timing).
     
  14. jamnmon66

    jamnmon66 Member

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    After reading tons about battery longevity and recommendations about max charge levels, I plan to keep the charge level as close to 50% as is practical for day-to-day driving. In other words, if you think the maximum that you'll typically use in a day is 40% of the battery (which is 124 miles according to the EPA rating), then cycle 20% above half & 20% below. In other words, for that example, set the max charge level at 70% expecting to not drop below 30%. If you think you'll use 50% of the battery in a day, set the max charge level at 75% expecting to stay above 25%. If your driving is variable then bump the number up as much as needed to eliminate range anxiety. When you're going on a road trip, charge to 100% the night before.

    My justification for this strategy is that it seems like the most wear comes from the amount of time that the charge level is at the extremes (high or low) particularly in high temperatures. But, it also seems that the thermal management is really good in the 3 reducing the potential wear from heat. And, hopefully the newer chemistry of the new cells in the 3 will also make them more resilient. But why not be conservative about it?

    Having said that, I've read posts from several people with higher mileage s/x that are apparently doing well so I don't think it's something to loose sleep over.

    Anyway, that was a very long worded way to recommend setting your max charge level as low as is reasonable for your driving habits. There's a good chance that will solve your original problem as a byproduct.
     
  15. jamnmon66

    jamnmon66 Member

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    The more I think about it, the amount of time your car takes to charge will be based on how much battery you used that day. Unless you upgrade your charger as you mentioned, the only way you can reduce how long it will take to charge the battery is to drive less. Just set it to start charging at midnight and if it goes over, so be it. That just means you needed the extra juice that day.
     
  16. TexasEV

    TexasEV Well-Known Member

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    Or you could just keep the charge level at 80 or 90%, enjoy the car, and not worry about a possible extra mile or two of range loss after many years.

    You don’t need a “strategy”. Let the battery management system manage the battery.
     
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  17. Rocky_H

    Rocky_H Active Member

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    This seems to be worrying about pennies. It would probably be pretty rare that it does go over the midnight to 7AM time window, like once every few months or so.(?) And if it does, it would be for a pretty short time, like probably only an hour or so. You will know if you ran your battery down really low the night before, so if you are concerned about it on that particular day, you can open the app on your phone around 7 or 8 the next morning when you wake up and press the button to stop the charging. I get some people's concern where their nighttime off-peak windows are like 1AM to 5AM, where it could use more planning and/or charging speed, but this midnight to 7 seems like a huge window that is no problem.
     
  18. Uncle Paul

    Uncle Paul Active Member

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    New owners tend to overthink these issues. After a short period of ownership you will figure what is best for your lifestyle.

    The car and it's charging system is pretty smart and efficient.

    As far as the OP's question. Tesla tapers off the charge rate as it approaches full. Even if it charges a little past your TOU discounted rate, the actual current taken may be very little.

    You will have this all figured out after charging a couple times.
     
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  19. Rocky_H

    Rocky_H Active Member

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    You're giving a false impression, even though there is some technical truth there, so it is not ever going to be relevant in this situation. Yes, there is tapering, but people will only see that at Superchargers or other high power charging--never from charging at home. This 32A charging at home is about 7kW. The tapering curve of the battery isn't going to get down to limiting that power level until about 98% full, which people just won't see, because they'll have their limit set at 90% or less.
     
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  20. Reid

    Reid Member

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    Disagree in this particular case. Every feature they add is work and adds complexity to the user experience, so it has to be justified.
    The problem I see is that if they cut off charging prematurely (let's say you get home at 4am after a late Friday night, and forget that it's set to stop charging at 7am), then you hop in the car at noon on Saturday to try to go somewhere, and you've only charged a bit, you'd be pissed. It would be a bad user experience and likely something someone might bitch to a friend about (even if it was their own fault).

    From the company's standpoint, it's better to NOT add the feature, charge the car to the state you asked for, and not care if the customer gets charged an extra buck on their power bill at the end of the month, and not give any additional credence to any range issues.

    Anyway, for this particular user, after 7am is probably not peak anyway; it's part peak, and the risk of going over is pretty small. I agree it's a case of overthinking something that will probably never be an issue.
     
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