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Charge cost with low mileage driving?

Discussion in 'Model S: Battery & Charging' started by Ev43, Jul 16, 2016.

  1. Ev43

    Ev43 Member

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    Hi all,

    I am in the process of having a NEMA 14-50 installed in my garage to home charge a Tesla Model S [yet to be purchased].
    I'm retired and I only drive approximately 3k miles per year. The car will sit in the garage for a week or two at a time without being used. When it is used it is most often just very short trips around town.

    What would you recommend be the most cost effective charging strategy for me? Would it make sense to leave it unplugged most of the time and only charge it once a week or so? Would that save electricity loss [vampire?] or not?
    I have read that leaving the car plugged in all the time when it is parked in the garage is best, but that sounds like it might be overkill, and costly, if I'm only driving it once every week or two.

    Thanks in dance for your thoughts.
     
  2. bhzmark

    bhzmark Active Member

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    leave it plugged in at 80%
     
    • Helpful x 1
  3. MountainRatMat

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    Not recommending it but wouldn't a 110v work for that use case?

    No need to dance.
     
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  4. TexasEV

    TexasEV Active Member

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    You don't need a "charging strategy". Tesla says to leave it plugged in. The car will charge when it needs to. Let the battery management system manage the battery.
     
    • Helpful x 1
  5. Ev43

    Ev43 Member

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    Oops.....sorry...the last line should have been "thanks in advance for your thoughts". I wasn't intending to dance! :)
     
    • Funny x 1
  6. jerry33

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

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    Leave it plugged in, but if you charge to 80% instead of 90%, charge to 95% about once a month (before you drive so that it doesn't stay at 95) to engage the balancing circuits. Note that the balancing circuits engage at 93% but because that's just an estimate... Once the balancing circuits are engaged, they will continue regardless of charge until they finish (which may take several days but it's automatic so you don't worry about it).
     
    • Informative x 1
  7. mblakele

    mblakele radial cross member

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    In California another good question is "which rate plan should I use?" Looks like you're in PG&E land? For a high-mileage driver I'd recommend an EV plan, but with low mileage E6 might work out better. You can tell the car when to start charging, so it waits for the cheapest rates.
     
  8. Ev43

    Ev43 Member

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    Many thanks. I was intending to check with P.G.&E. about a rate break. I wasn't aware of the "E6" plan though.
     
  9. mblakele

    mblakele radial cross member

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    Sorry, I should have checked my facts: PG&E closed E6 to new customers at the end of May. It's still worth looking at the available TOU options: Time-of-Use Plan | PG&E
     
  10. Ev43

    Ev43 Member

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    No problem. I will check my current usage [pun intended] and investigate options.
     
  11. jdw

    jdw Member

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    If you really don't drive much, you could consider charging to 70-80% and then shutting the car down. This would require you to turn the car on and maybe top off the charge before you drove, but would stop almost all of the vampire drain of a sleeping connected Tesla which is 1-3% per day.

    Turning the car off would save both electricity and battery cycles, but at the cost of convenience and connectivity. It takes a few minutes for the car to "start" from this condition, but if 70% or so charge covers your unplanned or emergency usage, then this might be an option for you.

    As mentioned above, when you do charge, charge before driving and to 90% with the occasional 95-100% charge, which helps to keep the battery balanced and calibrated.
     
    • Informative x 1
  12. ABCCBA

    ABCCBA Member

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    @Ev43 I drive very little, too. I happen to have both a HPWC and a 14-50. I use the HPWC for my MS. There have been times in the past few months since owning the car that I haven't driven one single mile in five or six days. I leave my car plugged up. What I have found is that the car drains (vampire drain) about 3 miles per day. When the battery drains a certain percentage, about 10 miles of loss, it starts the recharging process. I have experimented and have found that regardless of being plugged in or not, the losses are the same. So, the amount of charge needed to return to the 80%, 90% etc. point will be the same whether it is 10 miles at a time of charge or 30 miles of charge at a time. So, I have chosen to just leave the car plugged up and this way I know that it will have no less than a full standard charge minus up to 10 miles when I do get in and am ready to drive.

    I originally signed up for Tesla Logs to monitor all of the car's activities. I have since found TeslaFi.com and it provides outstanding statistics about the car's activities.

    But to answer your question directly, my opinion is to just leave it plugged in and the charge level set to 80% or 90%.

     
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  13. bmah

    bmah Obscure Member

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    @Ev43, I agree with the others that it's probably just easiest to leave your car plugged in.

    Another consideration is that once you get your car, you might actually find driving it to be so enjoyable that you find yourself driving more than you did before. Many of us have experienced this curious phenomenon. :)

    Bruce.
     
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  14. S4WRXTTCS

    S4WRXTTCS Active Member

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    Haha, retired plus superchargers? There is only one conclusion I can make from that, and it's total different than how many miles you think you're going to put on it.

    Anyways, I'm assuming from your mileage expectation that you're going to get a 60? the 60 actually has the 75KwH battery so there is no need to set the charge limit to 80% like you would do if you had a 75, or a 90.

    Just set the limit to 100% (which internally is 80% of the 75kwh battery) and leave it plugged in all the time. As Tesla says "a plugged in Tesla is a happy Tesla".
     
  15. FlatSix911

    FlatSix911 918 Hybrid

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    Here are some rough numbers to consider... hope this helps :cool:

    CA PG&E rates are about 0.15/kWh
    Therefore, 7kWh costs about $1.05
    Your can drive about 20 miles on 7kWh
    3000 miles per year = $157.50 in electricity cost.

    Bottom line, the fuel cost is insignificant for your low usage.
     
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  16. ABCCBA

    ABCCBA Member

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    FWIW - That example of casts equates to 43 MPG for an ICE at $2.25/gallon

     
  17. bmah

    bmah Obscure Member

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    On the PG&E EV-A tarrif it's closer to 0.10 / kWh if charging off-peak, so to reinforce what someone else posted up thread, it's a good idea to investigate other rate plans. (I am not necessarily advocating EV-A...that works very well for my usage pattern, but each owner needs to decide what's best for him/her.)

    Bruce.
     
  18. WannabeOwner

    WannabeOwner Member

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    Move to the UK for a better saving? :cool:

    Off-peak electricity can be similarly as low as $0.09 / kWh but petrol is about $ 6.48 per gallon (although our Imperial Gallon is about 10% bigger than a US Gallon)
     
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  19. AndreSF

    AndreSF Member

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    No matter how you choose to charge at home, IMO it will cost you less than what you would have paid for gas driving the same amount of miles. Like several other said, I would check your current rates/usage, but it's unlikely that EV-A plan makes sense in your scenario, unless coupled with some other options such as solar system as well as potentially power wall. I bet you are using A/C where you live! TOU rates are quite high during peak and that is when A/C is used mostly.
    The easiest would probably be just to stick with existing tiered plan you likely already have, but I would still recommend setting up a scheduled charging for your car (do it off peak at 11PM or so for smarter grid utilization) and just leave it plugged in.
     
  20. Ev43

    Ev43 Member

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    That's an interesting possibility Bruce!
     

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