The principle is correct. It can be realized in theory. You need a large-capacity battery and a constant-frequency inverter. However, to maintain energy conservation, the prerequisite is that your hand crank power must be greater than 350W (including power loss). However, the power of ordinary people is not that high, which is almost equivalent to half a horsepower. Moreover, although the computer power supply is 220V, 50HZ AC, it is still converted into DC 12V through the power supply. You might as well just use a hand-operated DC generator + large-capacity battery + DC voltage regulator for convenience.
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Electric vehicle batteries are composed of 12V batteries connected in series. You can just use one or several in parallel.
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Here the power is equal to the force multiplied by the speed. Through the speed change gear, the speed increases. What is the use of the small force? The efficiency of the gear is also reduced
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