A battery is a thing that is capable of holding an internal electric field. If you flow electricity through a wire it just heats up, it can’t store a meaningful amount of charge. A battery and a capacitor can store charge, partly because they are internally insulated, meaning electricity cannot flow around freely inside them to even things out.
In fluid flow a bucket is a bit analogous, you flow water into a bucket and it can store it. If you dump water on the grass it just dissipates. If you flow water through a pipe there is some storage, but not much. A bucket has walls and prevents the water from flowing out, so you can make use of it later.
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