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Slower the better?

Discussion in 'Model 3: Battery & Charging' started by karpetkutter, Aug 28, 2018.

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  1. karpetkutter

    karpetkutter Member

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    Ive been wondering now after owning my M3 for a few months now. Better to charge at highest amperage available with your Wall Charger (eg. 48 Amps, 40 etc) and be done in an hour or two depending on battery level or is it better to let it slow charge 5 Amps and charge all night?

    Just wondering anyone thoughts or habits?
     
  2. AnarchyEOD

    AnarchyEOD Member

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    I don’t think it matters much as long as you’re not charging to 100% everyday or letting it drop below 20% often.
     
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  3. karpetkutter

    karpetkutter Member

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    Yeah I always keep it between 20% and 80% but really just wondering. I would love a feature where you set it to at your set limit for your departure time. I really cant say ive read anything to say slow trickle charging has any advantages.
     
  4. brkaus

    brkaus Active Member

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    Slow keeps the pumps and such running longer. So I wouldn’t go too slow.

    I do 30a on my 40a (50a breaker) HPWC unless I need faster charging. Why? Why not..
     
  5. David99

    David99 Active Member

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    To the battery it really doesn't matter. It is a little more efficient to charge at the full rate. The reason is that the charger is more efficient at it's rated power. That's a common thing for power electronics. They are most efficient at the designed power. Partial power is less efficient.

    The other reason is that, while charging, there are few other system running that use energy. For example the pump to run the coolant through the battery and chargers, some fans and a few other things. So if you charge slower it takes longer and those extra systems run longer using more energy.

    Because of that I would recommend charging at full power.
     
  6. Rocky_H

    Rocky_H Active Member

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    @karpetkutter I was just talking about this in another thread:
    Is it normal for the wall connector cable to get hot @80 amps?

    It makes no difference for the battery. It can handle much higher charging rates than anything you have at home. Very very slow has a couple of minor downsides to it. Mainly, it's pretty wasteful, because there is some overhead losses in running the charging circuitry, and you are running that much much longer, wasting a lot of energy that isn't going to the battery. And there aren't a lot of battery studies that talk about this effect, because most people care about how quickly they can recharge a battery, rather than how slowly they can recharge it, but there is a minor degradation effect that happens just from how much time a battery is spending in that chemical recharging process. If you can get that over with quicker and let it go back to resting, that is a bit better for it.

    So as far as battery, you don't need to go slower. But as I referenced in that link, it may be a good idea to not run your charging equipment at its maximum level to not get it too hot. However, you said you have a wall connector. That is rated to pass 80A, and you're only using 48, so you have a good margin. The internal charger in the car is rated 48A max, though, so I might touch it down a few amps for the same reason if you can still get a full charge overnight.
     
    • Informative x 1
  7. ewoodrick

    ewoodrick Active Member

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    Slower charging definitely creates less heat, and that's good. 120V @5A may be just a little too slow to get anywhere. You definitely want to make sure that you can charge to make up the use. 5A is not much more than a driving round the block commute.
     

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