Does “electricty” or whatever it’s called that goes into your electric vehicle battery, have mass or weigh anything? My car has a 100KW battery. Is the weight substantially different when it has 0 charge versus when it is fully charged? It seems like a lot of energy goes into the battery, it must add to the net mass of the vehicle?
In: Technology
The answer is yes, your car battery will weigh more when fully charged. But that difference in mass is tiny. So tiny to be meaningless.
Electricity is an abstract concept; a series of linked phenomena, related to moving electrons around. Electricity doesn’t have mass, although some of the things that make electricity work (like electrons) do.
When you charge or discharge a battery you are moving electrons around (and depending on the kind of battery, doing a bunch of other stuff). But none of those ‘physical things’ are leaving the system or being added to it. No things being added or taken away, no change in mass, right?
However, when you charge the battery you are “storing” energy in it (how depends on the kind of battery). And mass is an expression of energy; the more energy something has, the more mass it has. That is mostly what the famous *E = mc^(2)* formula means.
A quick Google says EV car batteries store somewhere from 40-100kWh of energy.
If we plug that into our formula:
> m = E/c^(2)
we get 1.6-4μg. So around a millionth of a gram. Across the whole battery. Not much.
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