This is a very simple build Electronic Circuit Project of single solar cell trickle charges 3- to 16-v battery in-circuit. Many battery-powered applications use very little power when idle and have short-duration operating periods. Thus, the total energy used is very small. It would be convenient to incorporate solar cells in these devices to charge the batteries. However, the number of cells needed to charge a given battery voltage is close to Vb/0.6, thereby necessitating an array of solar cells, series connected. Single Solar Cell Trickle Charges 3- To 16-V Battery in-Circuit: The circuit in the figure addresses that issue by employing a self-oscillating boost circuit operating from a single solar cell. As such, it's able to trickle charge the battery continuously. The solar cell charges C2 until there's sufficient voltage to activate Q2. This will cause the output of U1a to turn on and latch on through the action of U1b. U1a's output also turns on Q3, which begins tra...