# Small solar panel dc to 5vdc for charging [closed]

I have a small solar panel which i want to use as cellphone, batties charger or any other gadget that requires 5vdc. I tried using 7805 but it reduces volts to 3.something. 7805 works fine on 9-12v battries. How can i do that. I need simple circuits because many ics used in those circuits may not be available here.My solar panel has

• Maximum power (Pmax) = 5w
• Voltage at Pmax (Vmp) = 17.2V
• Current at Pmax (Imp) = 0.30A
• Open circuit Volatage (Voc) = 21.6V
• Short circuit Current (Isc) = 0.31A

I think it has enough power to charge powerbank or cellphone.Is there anything usefull that i can pull from other circuits. I have plenty of them.

## closed as too broad by Bence Kaulics, Voltage Spike, Transistor, Peter Smith, Daniel GrilloAug 14 '16 at 18:01

Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer. Avoid asking multiple distinct questions at once. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

• Welcome to EE.SE and congratulations for at least posting the cell data. Your question is too broad at the moment and has already attracted one close vote. (4 to go.) Add a schematic of your circuit using the built-in editor button and use the node element to show your voltage readings at various points in the circuit. List the panel specifications using bullet points. It will make them easier to read. Then ask a specific answerable question. – Transistor Aug 12 '16 at 15:30
• @user6557161 please use the help center for guidelines on asking questions. – Voltage Spike Aug 12 '16 at 16:02

A simple linear regulator, such as the 7805 isn't going to work. The maximum current output of the panel is only 0.3A, while most gadgets will expect at least 0.5A. All the 7805 does is to reduce the voltage - it won't boost the current.

To boost the current, you'd need a proper DC-DC converter, perhaps a buck converter.

you can try two options.

1. With a battery
2. Without battery

I suggest the second option with LiPo battery. A solar charge controller like LT3652 will be very usefull in this case. This uses the concept of maximum power point tracking (MPPT) . There are breakoutboards available for those as well, like Sunnu Buddy from sparkfun.

I tried the same thing with a mobile powerbank and it worked perfectly. There is a chip inside power bank which trasfer 3.6v battery voltage to 5v. Tou can use dc to dc converters as well.

• Can i connect 3.6v battery directly with solar cell or reducing volatage is necessary here? – user6657161 Aug 12 '16 at 15:38
• No. You should use a solar charge controller as mentioned. Its a small chip. The battery/power bank can be commected to that controller. – Sanu - Open Maker Aug 12 '16 at 15:39