Why Can’t We Store AC in Batteries instead of DC?

Why Can’t AC Be Stored in Batteries Like DC?

Batteries are electrochemical devices that store energy in the form of direct current (DC). In DC, the polarity of the terminals remains constant i.e. one terminal is always positive (+) and the other is always negative (−). This matches how a battery naturally works e.g. storing and delivering energy in a fixed direction.

Right to the question, we cannot store AC in batteries because AC continuously changes its polarity i.e. 50 times per second at 50 Hz, or 60 times per second at 60 Hz. This means the battery terminals would need to alternate between positive (+) and negative (−) at the same frequency. However, a battery cannot switch its polarity back and forth at such high speeds, which is why AC cannot be stored directly in batteries.

Furthermore, if a battery is connected directly to an AC supply, it would charge during the positive half cycle and discharge during the negative half cycle. Since the positive half cycle cancels out the negative half cycle, the average voltage or current over one complete cycle becomes zero. Therefore, there is no possibility of storing AC in a battery.

To store AC, it must first be converted into DC using a rectifier (like in chargers and power supplies), and then the battery can store the converted DC energy.

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