Guys, at first sorry, because, I'm not good at English and describing something. Solar Power Bank is a new generation of Electronic gadget. It helps you a lot at emergency and also saves and reduce your electricity bill.

Its always useful if you have backup power always available with you, but what if the backup run out of power. Use the next best source of energy "SOLAR POWER". No, I didn't meant photo synthesis. All meant to use the solar power to charge your mobile or any usb devices.

So one day i thought about a solar power bank and searched in amazon, flipkart, ebay and even watched reviews in youtube, 90% of the are fake or charges the power bank a very little amount. So thought about why not make your own at that price, Seriously it cost me about 15$. So, not wasting your time, lets check out how made that, i hope you all like it...

Step 1: Tools & Materials Required

Any 6v solar panel, you can use 3w/5w solar panel for more Amps (PLEASE WATCH REVIEWS BEFORE BUYING IT ONLINE)
IN914 diode (to prevent current flow to opposite side)
OTG or data cable micro/mini usb according to your phone.
TP4056 module
DC-DC 0.9V-5V to 5V Converter USB Step Up Power Boost Module
18650 battery (from old laptop battery or you can buy it) 2pcs for more amps
on/off switch
wires
soldering equipments
wire cutter
plastic container with enough space

If you have got all these parts, then lets make the solar powerbank.... :)

Step 2: So, Lets Make the Solar Panel, Charging Compatible

take the in9148 diode and identify anode side

The black strip points to the cathode part, the oposite side is anode.

solder the anode part to the +ve of solar panel.
solder a red wire(red to mark as +ve) to the cathode part of the diode.
solder a black wire to the -ve part of solar panel.
now cut an otg into halves, and take the micro/mini usb part.
You will see 4 wires side by side, among those we need only the red and black ones, so cut the green and white wires(They are used for data transmission purpose).
Solder red wire of otg to the red wire of solar panel and black wire of otg to the black wire of solar panel.
Add tape or heat shrink tubes to the joins.

Now your solar panel is ready to charge any usb device BUT REMEMBER GUYS DO NOT CHARGE YOUR USB DEVICE(EXCEPT POWER BANK) DIRECTLY WITH THE SOLAR PANEL AS SOLAR PANEL DOES NOT PRODUCE CONSTANT CURRENT and THE VOLTAGE ALWAYS RISES AND FALLS BASED ON THE DAY LIGHT.

So now we will make the power bank. . .

Step 3: Making of the Power Bank

Before making it I want you to know which part is going to be used for what reason.

WHY USE 2 or more 18650 Batteries??

Most of the 18650 Charge cut-off voltage: 4.2V

Our goal is to make a power bank which can charge our phone completly, each 18650 battery provides 2200 mAh current minimum. Now a days mobiles comes with 2500-5000 mAh batteries. So more the batteries more the current.

But 1 thing to remind that, we need to solder batteries parallel, as parallel (++ / --) batteries increase amps but in series (+ - + - ) it icreases voltages.

so if we solder in series it will produce 8.4 v 2200mAh current

In parallel it will produce 4.2 v 4400mAh current which is enough for a mobile or any other usb devices. . .

so at first solder the +ve part of both batteries and -ve part of both the batteries as diagram above

you may use 18650 battery holder but make sure its in parallel.

HOW TO IDENTIFY +ve and -ve part of 18650 battery

DC DC Converter Step Up Boost Module 3V To 5V 1A

input voltage: 2.5-4.9V.
Output voltage: 5V.
Output Current: the maximum 1000mA.
Red light means it charging the phone.

It produce constant 5v 1A(1000mA) current. So it can charge your mobile at same time as normal charger does.

TP4056

It takes power from the mini usb port, and charges the batteries..

red light means its charging, and blue/green light means fully charged

Description about tp4056

NOW MAKING THE POWER BANK

place the tp4056, boost converter, switch in the container and mark out with pencil/marker where to make holes for the usb ports and switch. make holes and cut proper size of wires.
use double sided foam tapes where you are putting the parts including battery.
put all parts in the container and use some hot glue so that they does not misplace
Now solder proper wire, so that you can understand easily as per diagram.
if all soldering is done, add some hot glue to adjust the wires.