It should be analyzed on a case-by-case basis. The battery capacity must be determined to calculate the charge. Assuming the battery pack is 72V50AH and empty, an hour of charging can be charged into about 1 KWH, or close to a quarter of the battery capacity.
Let's say the battery pack is 90% charged when it starts charging, because it's about to enter the trickle charging phase, and the charge will be much less.
Not much, maybe a bar or so
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If the electric vehicle battery is 72 volts, the battery is 20AH, and 1.44 KWH of electricity is required
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72 * 20 = 1440 w.h = 1.44 kw.h
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That means it takes 1.44 kilowatt-hours of electricity to be fully charged