Is solar power bank useful?

First of all, the solar panel receives solar energy and converts it into electrical energy, the electric solar panel at this time is like a battery (if you have learned the circuit, more professionally it is a current source), but the output voltage, current, power of this battery are not constant, it is affected by temperature, light, load, etc., can not directly charge the battery, nor can it directly charge the mobile phone, which is also the reason why I failed to do solar charging for the first time.

To charge the mobile phone, the power of the solar panel needs to be converted into the power that meets the charging needs. For example: too much current, will burn out the battery, the voltage is too low, can not be charged, the power is too small, the charge is too slow. This requires the addition of two power conversion circuits between the panel and the battery: MPPT, which is called maximum power point tracking, which can make the solar panel work at maximum power all the time (the power of the solar panel is variable, affected by many factors, and the output zero power is also possible), some solar power banks omit the MPPT link, so that the charging efficiency will be reduced and the charging time will become longer.

There is also a battery charging circuit, which can ensure the voltage and current required by the battery during the charging period, and control the charging current within a safe range.

After the battery enters the battery, the subsequent link is the same as an ordinary power bank. First of all, the voltage range of the battery is 3.3~4.2V (single cell, the general charging treasure is multi-section parallel, notebook charging treasure has multiple sections in series, the voltage will be high), and the mobile phone charging voltage is 5V, which requires a boost circuit to raise the voltage to 5V while controlling the charging current. Now many mobile phones support fast charging, if charging such mobile phones need to add a fast charging chip, the chip can identify the fast charging protocol inside the mobile phone, so as to determine whether you need 5V2A general fast charge or 18W fast charge, or charge 5 minutes to talk for two hours of fast charging.