It can charge any size of the Gel cell batteries and extend the life of the Gel Cell battery. While the circuit is running, the LED indicates charging.
This is LM317 Low dropout regulator 5V 2A using TIP41, The voltage input is 5.1V DC is converted into 5V output,while maximum output current to 2A by TIP41 [...]
This is a USB 5V to 1.5V Step-Down Converter Circuit. When we use a Cheap MP3 Player which use only one 1.5V AA battery as its power supply.