The voltage of the solar power manager needs to match the solar panel being used. The solar power manager in this tutorial meets the need of a 6V-24V solar panel, has a 3.7V 14500 lithium battery holder, and a ph2.0 connector for other types of 3.7V batteries.
For recommandation, you can buy a 6V solar panel with 250 – 300 mA working current if you would like to use a common 3.7V rechargable battery. Solder the solar panel with wires like below (some solar panels have direct cable connections; in that case no soldering is needed).
An autonomous supply of electricity by means of rechargeable batteries would be ideal. The ESP8266 solar panel power supply is of course an obvious solution. During the day, the microcontroller is supplied with electricity from the solar cell and a battery is charged at the same time. This energy storage device is then used at night.
In order to regulate the voltage from the solar panel normally a voltage regulator circuit is used in between the solar panel output and the battery input. This circuit makes sure that the voltage from the solar panel never exceeds the safe value required by the battery for charging.
Hannah Bonestroo’s tutorial provides a detailed description on how to choose the right solar panel with the right batteries. First, the solar panel should have at least 1.5 times the voltage of the battery. A 3.7V rechargable lithium ion battery should be charged by at least a 5.55V solar panel.
Second, the capcatiy of the battery, determined by milliamps per hour (mAh) should be around ten times the working current (divide by an hour) of the solar panel for the best efficiency. For example, a battery with 3500 mAh should be powered by a solar panel with around 350 mA of working current.