Many threads on these forums say that charging at 120V / 12A is less efficient than charging at 240V / 40A.
Most of the reason for this observed inefficiency, I think, is the constant level of vampire drain from the car's systems. So for example, if the car uses 500W constantly, that's a much bigger fraction of the 120V / 12A charging power than it is of the 240V / 40A charging power. So 120V charging is not just slow, but disproportionately slow.
From the practical standpoint of "how long will it take the car to charge?" I can understand calling this "inefficiency." But it really doesn't say anything about the energy-efficiency of the battery charging itself. It's just a constant, additional load detracting from the power available to charge.
Consider the following thought experiment: Take two identical cars with identically-depleted batteries. Plug one into 120V / 12A and the other into 240V / 40A. Leave *both* vehicles plugged in until *both* are charged to the same almost-full level. (I.e. the 240V-charging vehicle continues to incur vampire losses after it's done charging.) At that point, will the electric meter have spun further for the 120V charge, or not?
Thanks...
Most of the reason for this observed inefficiency, I think, is the constant level of vampire drain from the car's systems. So for example, if the car uses 500W constantly, that's a much bigger fraction of the 120V / 12A charging power than it is of the 240V / 40A charging power. So 120V charging is not just slow, but disproportionately slow.
From the practical standpoint of "how long will it take the car to charge?" I can understand calling this "inefficiency." But it really doesn't say anything about the energy-efficiency of the battery charging itself. It's just a constant, additional load detracting from the power available to charge.
Consider the following thought experiment: Take two identical cars with identically-depleted batteries. Plug one into 120V / 12A and the other into 240V / 40A. Leave *both* vehicles plugged in until *both* are charged to the same almost-full level. (I.e. the 240V-charging vehicle continues to incur vampire losses after it's done charging.) At that point, will the electric meter have spun further for the 120V charge, or not?
Thanks...