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Does charging at a lower rate give me any benefits?

Discussion in 'Model X: Battery & Charging' started by Ramisanders, Oct 26, 2016.


Do you lower your AMPs if you have the time?

  1. Yes

  2. No

  1. Ramisanders

    Ramisanders Member

    Jul 3, 2016
    Some days I drive very little. And I have a Tesla Power charger that's charges at 48amps and usually takes 2-3 hours to charge to 90%.

    I've been reducing the AMPs to 10 and allowing it to charge overnight for 6 hours.

    I feel that if I have the time I should lower the amps and give the car a slower less aggressive charge. Is this accurate ?
  2. Saghost

    Saghost Well-Known Member

    Oct 9, 2013
    There are a few benefits to the lower charge rate. It keeps the battery warm, it lowers the thermal stress on the EVSE and charger, and it may reduce your electricity bill, if you have a demand charge and lower the rate consistently.

    Aside from keeping the pack warm on cold days, the battery doesn't really care much - all the AC charging rates are so slow that slowing it down won't matter for the chemistry.

    Very slow charging rates are less efficient, because the percentage of power spent on overhead rises.

    I think I saw an analysis somewhere here that said the most efficient rate for an early S was around 25A at 240V?

    That might apply to the new chargers, or it might not.
  3. Cyclone

    Cyclone Cyclonic Member ((.oO))

    Jan 12, 2015
    Charlotte, NC
    I use 30 amp on 247 volts so my mobile connector cord doesn't get hot. Whatever charging efficiency I lose at 30 amps instead of 40, I likely gain from lack of wasting energy converted to heat.
  4. TexasEV

    TexasEV Well-Known Member

    Jun 5, 2013
    Austin, TX
    No this is not accurate. You're actually wasting electricity doing so and there's no benefit for the car at all.
  5. Electric700

    Electric700 Active Member

    May 21, 2013
    Florida, United States
    Interesting points. Ramisanders, if there is a concern about the effects of the higher current and heat generated over the long term, perhaps lowering the current to 40 A would be better. Also, you could set the car to charge about 3 hours before you actually need to use it. This way it won't be sitting at a higher state of charge.
  6. Rocky_H

    Rocky_H Active Member

    Feb 19, 2015
    Boise, ID
    There are a few items in the path of charging the car, each with their maximum level they are built for, and it may be slightly beneficial to back off from the maximum a little, but 10A is really overdoing it, and you're just wasting energy by running the charging system for longer than needed by going that low.

    Your wall unit max is 80A--you're already well below that.
    The charger in the car is either the 48A or upgraded 72A version. Being a little less than that may be helpful.
    The battery of the car can handle 300A or so, so all of this is already way below its maximum.
  7. TacC

    TacC Member

    Jun 2, 2016
    East Bay, CA
    The BMS should minimize any potential issues associated with charging speed.

    If you've got a free hour or so then this video may be worth your time.

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