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DIY USB 5V Solar Power Bank

The solar panel used in the project is rated at 6V and 150mA which provides about 0.9W/h in ideal conditions and the Li-Po battery is rated at 3.7V and 4000mah which can deliver approximately 15W/h. We can see that charging will last much more than 15 hours because the efficiency of storage and step-up conversion will be less than 100% and the energy we can harvest from the sun depends on the time of the day and angle of the light beams. We can easily say that it will take days to fully charge the battery by using this solar panel. Since the solar energy is free, any percentage will be of profit.”

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