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Home Charging Best Practices

Discussion in 'Model S: Battery & Charging' started by flipb, Sep 29, 2016.

  1. flipb

    flipb Member

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    I just brought home my 2013 CPO Model S 60kwh (twin chargers, supercharging) a couple days ago.

    For the first couple of days, i've had it plugged into a 120v 15a outlet using the Mobile Connector. It charges at 12a, at a rate of about 4mi/hr. This has been sufficient to recharge fully to 90% overnight, based on my daily driving of 25-30 miles per day.

    I now have a NEMA 14-50 50amp outlet installed in my garage, adjacent to the existing 120v outlet.

    Based on my driving habits (average ~30 miles/day), what's the best practice for health of the battery?
    1. Charge from the 14-50 with charging amperage set to 40a
    2. Charge from the 14-50 with charging amperage set to something lower (15a? 20a?)
    3. Charge from the 120v at 12a
    (I don't get discounted utility rates at off-peak hours, so there's no inherent advantage to charging quickly in the wee hours vs. charging slowly throughout the night.)

    Thanks.
     
  2. msnow

    msnow Active Member

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    For the health of the battery it doesn't matter.
     
  3. DarkMatter

    DarkMatter Member

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    Plug it in to the 14-50 and let it run as normal. It will be the most efficient at 40A and you will never have to think about it.
     
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  4. Bheuring

    Bheuring Member

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    I was told from a friend who does electrical work that 220 is always more efficient and cheaper then 110
    A question I would have is witch one is better for the battery
     
  5. ICETOO

    ICETOO Member

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    My recommendation is to charge via NEMA 14-50 and:
    1. Charge when battery level is around 50% (sweet spot for Li-Ion Batteries)
    2. Limit charging ampere to 32a (if you don't need it charged faster limited draw might help battery last longer)
    3. Set limit to 85-90%
    Other than that these batteries are quite robust and will last a long time.
     
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  6. DarkMatter

    DarkMatter Member

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    Seriously don't over think it. You'll just end up down a rabbit hole of conflicting information. Plug it in, the difference will be 1% in ten years if anything. These cars manage the battery for you.
     
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  7. TexasEV

    TexasEV Active Member

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    Agree. Plug it in to your 14-50 outlet at 40A and let battery management system manage the battery.
     
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  8. DiamondDave

    DiamondDave Member

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    It's my understanding that charging on a 120V circuit uses 50% more energy than charging on a Level 2 circuit like your 240V NEMA 14-50 outlet. You used to be able to see that on Tesla's website on the charging calculator. I don't know if it's still there, I haven't looked at it in a while.

    You went to the trouble to have it installed, go ahead and use it!
     
  9. AEdennis

    AEdennis Active Member

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    @flipb

    We've put on over 65,000 miles on our Model S charging split equally on 40A Level 2 and 30A Level 2 (As I updated on my thread here, we have many outlets and EVSEs at home.) Battery degradation has been minimal.

    That being said, we just added a new HPWC on a 70A circuit to start charging at 56A (primarily for my wife's Roadster, but will use for Model S if in a "rush.") In the meantime, I've been using 30A because I have the Model S plugged into an EVSE that I got for our old ActiveE and it is "humming along."
     
  10. Canuck

    Canuck Active Member

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    You have dual chargers which is great but charging daily at 40 amps only uses the one, which is liquid cooled and prone to wear, so if anything, the concern should be for that charger failing over any potential battery degradation, while your slave charger is doing nothing and not wearing at all. A UMC is also lightweight compared to a HPWC and is more prone to failure than any concern for the battery. What I did, was I got a HPWC, put a 14-50 plug on it, and plugged it into my outlet instead of my UMC. I don't need a full 80 amps at home. I do at my cabin where I hardwired a HPWC and run it at 80 amps. But at home, I set the dip switches in the HPWC to lower amps (50 or 64 depending on the version), then I set the car to 42 amps. That way, it ramps up to 21 amps, pauses, then ramps up to 42 amps. What that shows it that each charger in the car is getting 21 amps (far less stress on the master than 40 amps and less cooling required) but you are still charging at 42 amps. Technically, for a 50 amp breaker you should only be drawing 40 amps, so I do NOT recommend anyone doing this. Plus, people say their car sometimes fails to remember dialed down amps. Mine never does, but others do and that could be a problem. So I'm just saying what I'm doing -- while recommending against it. I think it's best for the life of the chargers in my vehicle, my lightweight UMC stays in my car in case needed, and I didn't have to hire an electrician to wire in my HPWC at home. You can just buy a 14-50 stove plug at Home Depot which I've read others here have done to plug in their HPWC's. I bought the wire and plug separately.
     
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  11. Rocky_H

    Rocky_H Member

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    Lots of good answers here. You asked specifically about the health of the battery, and @msnow answered that really simply. None of that will make any difference for the battery. What you didn't ask, though, and I will give some advice on is for the charging equipment. The mobile charge cable has been found by many people to get pretty hot running at its maximum level of 40A. Heat and especially heat cycling of hot/cold/hot/cold every single day isn't good for the long term life of electronic components, solder joints, etc., and some people have seen their UMCs fail within a year or two. I would recommend turning the current down to maybe low to mid 30's amps, and it will be cooler and probably last longer.
     
  12. Thomas Allen

    Thomas Allen Member

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    I agree. Charging at 30 amps or less (I charge at 24) makes everything run cooler, and that's better for your car's electronics, the UMC, and the wall outlet.
     
  13. msnow

    msnow Active Member

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    Wait, @Rocky_H was talking about the UMC which is correct but you added in the "car electronics" which is incorrect. The OP can charge at any amperage he wants without damaging his car.
     
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  14. scottm

    scottm Active Member

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    The simple answer is, you can't use both chargers at home because you can't get over 40A on the NEMA.

    Charge however fast you need or want to recharge.

    You can probably prolong the life of the mobile charger, NEMA socket, NEMA plug on the charger, and the in-car charger by dialing down to something less than 40A. Less heat.

    I second what @ICETOO already said. That would be my habit in your circumstance.

    I have a HPWC and used to charge at 80A all the time, car set to 80 or 90%. The handle of the HPWC began getting too hot to touch.. and was replaced under warranty. Now, I charge at 64A to split the load and reduce overall heat and stress on everything.

    The car remembers the Amperage setting last made in my garage, so it now defaults to 64A there.

    If I did need 80A for a quicker charge... for some reason, I wouldn't hesitate to dial that in.
     
  15. cvrcv

    cvrcv Member

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    Charge at the highest amperage available. Aux losses are too high for anything else to matter.
     
  16. msnow

    msnow Active Member

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    What do you mean by auxiliary losses are too high. Source?
     
  17. scottm

    scottm Active Member

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    I'm guessing Aux losses = vampire load

    in that vampire loss exceeds charging efficiency reduction of using lower power settings or source while charging

    How'd I do?

    This may be true. However, I have a Ctek battery maintenance charger on my 12V battery while parked, which effectively reduces my vampire loss to zero, while charging, or not... The vampire feeds off my maintenance charger output so the contactors never close to recharge the 12v from the tractor battery while the car is in my garage.

    Fewer cycles... better life.
     
  18. msnow

    msnow Active Member

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    Maybe I'm not seeing it but if I do a 90% charge at 10A or 80A the vampire loss will be the same after it's charged no matter what amperage is selected.
     
  19. scottm

    scottm Active Member

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    Charging at 10A is less efficient than charging at 80A, efficiency is a loss while charging.
    Vampire is continuous before, during, and after charging.

    I think the statement was (poster can confirm) vampire loss exceeds efficiency difference between 80A and 10A, so it's moot. I actually don't know or care to work out the math. And really, just another way of complaining about vampire loss.
     
  20. Rocky_H

    Rocky_H Member

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    Right, it's not actually vampire losses he was talking about. It's the overhead energy usage of running the charging circuit. It takes a certain amount of power to run the charger in the car. If you are using a low power source, like 120V 12A, that is 1,440 Watts. It seems to be about a fourth to a third of that just goes to running the charger and is not going into the battery, plus you are running the charging for many hours, wasting that energy for longer. If you use a higher power level, that same overhead is there, but it's a much smaller percentage wasted and it's for less time.
     

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