14.47 kwh per full charge

Discussion in 'Clarity' started by JulianClarity, Aug 14, 2019.

  1. Robert_Alabama

    Robert_Alabama Well-Known Member

    The 10.9A would be a good bit less in losses in the 50' #12 extension cord. I calculate 217 W as the loss for the extension cord at 11.5 hours to charge with 0.1588 Ohms for the resistance of the extension cord. So even if the contacts heat a little, I'd bet it isn't more than 300W losses per charge. This little exercise did make me realize that you do pay a penalty for faster charging at 240V, since losses are probably less at 16A than at 32A. If all wire were the same from EVSE to car, losses per hour are 1/4, but charging takes twice as long, so you end up saving half of the losses. With the smaller wire size for the 16A EVSE, there are more losses, but I bet losses are still 25% less for the lower amperage. I'd guess that those using the 12A OEM EVSE at 240V would cut losses to at least half that of charging at 32A.
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  2. MNSteve

    MNSteve Well-Known Member

    First I want to point out that the loss related to charging is not significant. Certainly it's worth some discussion and to be minimized when possible but not to be obsessed over.

    I don't agree that losses are generally higher with level-2 charging. Sure, if you ran the same current through the same wires, they would be larger ... but that is not what you are doing. The connecting cables for level-2 charging tend to be shorter and of higher gauge. Without specific data, it's not possible to calculate the heat losses in the connecting cables. But I would speculate that losses related to the charging components in the car will be less since the time spent charing is so much less, so overall I would expect better efficiency from a level-2 charger.
  3. Robert_Alabama

    Robert_Alabama Well-Known Member

    @MNSteve, my statement was poorly written. I wasn't trying to say that 240V charging losses were higher than 120V losses. I meant only to compare faster charging at 240V vs slower charging at 240V and say that the losses are less for the slower charging (32A vs 16A vs 12A at 240V). I'm not sure about the losses related to charging components. The slower charging probably needs less cooling from the car, so I bet you save some there even though the components are active longer. But I agree that the difference in charging losses over the lifetime of the car between any method of charging probably isn't going to be a significant figure.

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