There are several reasons for this:
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1. The actual output voltage of the charger is too low. Usually the output voltage of the charger should be about 5V, if it is too low, it will not be able to charge the charging bank normally;
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2. The wire diameter of the charging line is too thin, the loss is too large, and the actual voltage provided to the charging bank is too low;
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3. The voltage detection part of the built-in control board of the charging bank is abnormal.