This is a simple DIY iPhone charger circuit that can be built with a few resistors.
First, you need to buy 4 resistors with this values: 2 of 50 kΩ, 1 of 100 kΩ and 1 of 150 kΩ.
Ok, you got 4 resistors, now you need a 5V power supply, you guessed it, another USB cable. An USB cable has +5V on pin 1 and -5V (or ground) on pin 4.

If you can handle a cutter, gently cut off the isolation and reveal the wires inside. See what colors the wires have that are connected at pin 1 and 4. Note or remember and then with an soldering gun solder the cables to the iPhone charger circuit like in the schematic. continue reading…

The LT3650 circuit is a monolithic two-cell Li-Ion/ Polymer battery charger that operates from 9V to 32V input voltage range (11.5V minimum start-up voltage). The LT3650 si produced by Linear Technology and provides a constant-current/constant-voltage charge characteristic, with maximum charge current externally programmable up to 2A, set using an external current sense resistor. continue reading…

So a battery is charging during daylight from a solar panel and can discharge through solar panels during night. This problem can be prevented with a diode but this has a disadvantage so we use this switch.
This solar panels switch circuit replaces the diode and connects the panel to the battery through a relay contact. This is powered by the panel. When the supply voltage is low, the relay wont act so the battery is not connected to the solar panel. continue reading…