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What Charge Current setting should I use?

Discussion in 'Model X: Battery & Charging' started by plasmo, Oct 21, 2016.

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  1. plasmo

    plasmo Member

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    I noticed that the charge current can be adjusted, and my X is currently set at 35Amps. I have never changed this setting. What is the standard setting that one should use? Should I bring this up to 40Amps?
    (using a 240v outlet / NEMA 14-50 outlet)
    thanks
     
  2. Saghost

    Saghost Active Member

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    If it is showing 35 Amps, the car probably dropped the current down from the 40A it started at because it saw an excessive Voltage drop. Unless you need to have the faster charge for some reason, I'd probably leave it at the safer, lower current level.
     
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  3. TexasEV

    TexasEV Well-Known Member

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    The current setting sets itself based on which UMC adapter you're using, but it's GPS based so once the current is reduced at a certain location it stays that way until you manually set it up again.

    There is no reason to leave it at 35A. Put it back to 40A, and if it drops again that may be an indication you have a wiring problem in your outlet. Or it could be many other causes-- search for "charging drops to 30A" and read the threads.
     
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  4. Rocky_H

    Rocky_H Active Member

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    I and several other people would disagree that there is NO reason. Both the mobile charge cable at the maximum 40A and the wall connector at its maximum 80A have significant heat. Running them at a bit lower current keeps them noticeably cooler. And since heat and especially heat cycling, where something swings by many degrees from cold/hot/cold/hot every day, is a main cause of degradation and material stress in electronics, there is some thought that your charging equipment can last longer if it is not getting as hot every day. Depending on how far you drive, if it takes 5 hours to recharge or 3 hours to recharge while you're sleeping, that probably makes no difference to you, but you can likely help your equipment last longer by not stressing it as hard every single night. Occasional use at 40A is still fine, but for daily use, a little less current will probably help it last longer.
     
  5. Canuck

    Canuck Active Member

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    I'm with @TexasEV. Put it back up to 40amps to see if it dials itself back down again. Tesla's BMS is so good, you don't need to worry about charging at 5 amps less. Charging at a Supercharger is not even harmful since the heat is managed. But you should find out why it dialed itself down and there may be days you need that extra 5 amps.

    I charge at 80 amps at my cabin and heat to any of the equipment is not a problem. Tesla wouldn't be selling the equipment, and it wouldn't meet code requirements, if there were issues in using it as intended.
     
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  6. TexasEV

    TexasEV Well-Known Member

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    I've charged with my UMC at 40A every night for more than 3 years and it still works fine.
     
  7. Rocky_H

    Rocky_H Active Member

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    #7 Rocky_H, Oct 26, 2016
    Last edited: Oct 26, 2016
    "I have one personal experience data point."
    And plenty of other people who run them at 40A have had to replace their UMCs a couple of times. Whatever. The science is sound--heat degrades electronics.

    I should probably also elaborate since you're saying it is fine because it has been fine for 3 years. We're talking about lifetime degradation. We're talking about metal fatigue and stress of solder joints that is cumulative from heat cycling. This kind of stuff doesn't make something fail the first time you use it, but it may be the difference between it lasting for 2 or 3 years and maybe it lasting for 6 or 7 or more years.
     
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  8. balefire

    balefire Member

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    At rates below 40A, there is greater inefficiency in the charge. In other words you are wasting energy charging your car.

    Conversely 80A is the most efficient at home. But the gain in efficiency is less than 1% between 40A and 80A.

    Ive charged at 40a for more than three years with no issues. For me it is the sweet spot between battery health (keeping it cool) and wasting kwh
     
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  9. TacC

    TacC Member

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    This pretty much covers all angles. Great post.

    Charging at lower amperes is less efficient and puts the battery in a higher SOC for longer. Increasing the amperes will cause your battery and UMC to run hotter.

    Given that we're talking about a Model X and UMC, it might be that none of this adds up to more than a few percent/dollars in terms of expected life/cost over the course of five years.
     

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