This solar charger can only output enough voltage and current under bright sunlight, especially in winter, or in the case of insufficient sunlight, or the solar cell area is too small, can not provide sufficient voltage and current, so it is difficult to charge, if the device being charged (such as mobile phone) is in the boot state, then not only can not charge, but in the consumption of voltage It's going to get lower and lower.
So it is best in the summer or at noon, or with a sunshine tracking system and timing control, the effect will be better.
Insufficient solar power leads to less charge