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110 Volt overnight charging

Discussion in 'Model X: Battery & Charging' started by Keiki, Feb 21, 2017.

  1. Keiki

    Keiki Member

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    Living in Hawaii/Honolulu we drive relatively short distances. 20 miles per day for a 7 day week is probably more miles than I would do ( it's only approximately 80 miles around entire island of O'ahu).

    My question is; would an overnight charging at 110 volts (on a daily basis) cause harm to a Tesla car battery?

    I typically drive less than 20 miles per day, usually car sits at least 1 day with out starting. We tend to walk quit a bit here, our dog loves that as do we.
     
  2. Lloyd

    Lloyd Well-Known Member

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    It would likely work just fine. Keep it plugged in while at home and you will get 30 to 40 miles per day.
     
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  3. Keiki

    Keiki Member

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    Thanks Lloyd. That would be much more than I would need and a considerable installation cost savings.
     
  4. Derek Kessler

    Derek Kessler Member

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    It will do harm to your electric bill, however. 110v is the least efficient method to charge a Tesla. Though with the amount you're driving, it'd take several years to make up the difference when it comes to the installation cost of a higher power charger.
     
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  5. Lloyd

    Lloyd Well-Known Member

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    Thats not huge, maybe 10% at most.
     
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  6. daniel

    daniel Active Member

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    Charging at 110 volts will do no harm to the car. It will be slow, and if occasionally you drive a couple of times around the island in one day, it may be a few days before it is again fully charged, but that will not hurt anything.

    Is it really less efficient? The low charging rate would mean less heat that needs to be dissipated, would it not? That should improve efficiency.

    In any case, the amount of energy used would be small due to the low number of miles driven.
     
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  7. BerTX

    BerTX Active Member

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    The number I have seen used on TMC is 90% efficiency at 240v and 70% efficiency at 120v. True, you don't drive much, but if your electricity is $0.33/ kWh (price of living in paradise, and all that), then I think that works out to about $12 extra per month for 120v charging vs. 240v.

    I'm sure someone will check my math, so I won't bother showing my work.o_O
     
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  8. JHWJR

    JHWJR Member

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    I have heard it explained that there is a certain power overhead to run the charger in the car, and it's basically the same whether you are running at 110v 3-5 amps, or 240v 25-30 amp, or 240v 50 amp. So, at 110v, less power is left over to charge the car. It therefore costs more. But I like BerTX's math above. Sounds about right.
     
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  9. Missile Toad

    Missile Toad Member

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    back-to-future-ii-mr-fusion-home-energy-reactor-replica-3.jpg Some quick math. Assume 240v installation gives 20% better efficiency than 120v, then:
    10000*.29*.12 are (miles, annually)*(Whr/mi)*(local electricity $/kWhr) = $348 ... multiplying by the 20% differential ~ $70.
    HPWC goes for $500 plus $400ish for install makes in $900. Thus, approximately 13 years to pay back the install cost, or 130,000 miles charged at home. It all works out, as long as somebody doesn't invent Mr. Fusion by 2031.

    See Tesla — Wall Connector with 8.5' Cable.
     
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  10. daniel

    daniel Active Member

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    ^ The OP probably pays around 30 cents per kWh, and only drives around 7,300 miles per year. (High electricity cost in the Hawaiian islands, and you never drive terribly far.)
     
  11. scaesare

    scaesare Well-Known Member

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    There is a difference in efficiency and overhead.

    Efficiency typically has to do with power-losses incurred within a system, in this case the UMC & the in-car charger are the major components. They cannot convert 100% of the energy from AC to DC to deliver to the pack, but 90+% is attainable. I've seen 94-98% clamed for the Tesla chargers. Note that often lower currents are more efficient due less resistive losses.

    This is different than the overhead associated with the car running it's systems. The car can consume something like 300-400W when parked. So if you are charging at 120V/12A (1.44kW), and the car eats 400W of that, then only ~75% of the energy delivered by the output side of the charger (after losses) is going to make in in to the battery.

    If you are charging at 240V/40A (9.6kW), then ~96% of the charger output is making it to the battery, with the rest being eaten by the car's systems while idle. (Bothe examples above ignore the few percentage points of charger inefficiency)

    But in both those cases, that's car overhead accounting for the major loss, which doesn't affect the charger efficiency. The car is going to consume 400W/hr regardless if you are charging at 120V, 240V, or not at all. It does, however, have an impact on how much time it takes to charge the battery... so whether the car saps that energy from a slow charge rate all night... or the car saps it from the fully charged battery after you finish charging at a higher rate, makes no difference, really.

    All of which to say, the point made about the impact to your efficiency, while there is undoubtedly some variation in efficiency at different input voltages, it's not enough to get worked up over, IMO.
     
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  12. Dax279

    Dax279 Member

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    Looking on PlugShare you might have some alternative charging options as well if more is ever needed.
     
  13. FlyF4

    FlyF4 Member

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    Took the words right out of my mouth. TOTALLY agree.
     
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