I had this old iPhone 3G, its battery life was terrible and I didn't had enough money (at that time) to change the phone or the battery or to buy a power bank. I had to charge the phone at least 2 times a day , so that I can attend few calls. But I had few of the things needed to built a power bank and this is what I have done to keep it alive. The cost of making power bank alone was just around US$3 or so.
Oh forgot to mention that I added solar panel for charging under sun too...
Step 1: Stuffs You Need
This was made using most materials that was on hand including solar panels and other misc items, only had to buy the Lithium battery charge controller and the step-up module to keep the power bank small. The materials used in this project are as follows,
Items I had on hand:
1. 18650 cells extracted from old laptop battery, if you want to know how click here.
2. 18650 case
3. Solar panel 5.5V 160mA
5. 2x 1N4007 diodes
6. Velcro strips
7. Hot Glue
8. 47 ohm resistor
9. Scrap metal tabs salvaged from the laptop battery.
10. Small slide switch or any other type is fine.
Things that are bought:
1. Lithium battery charger board with micro USB. I bought for $0.99 from ebay link below,
2. 5v 1A output Boost Step-up module, bought from the same seller for $0.99,
1. Soldering Iron
2. Utility Knife or side cutter
4. Helping Hand (useful but not necessary)
Note: I forgot to add a 18650 protection circuit, since the battery extracted from laptop battery does not have them. So if you are using a battery without protection circuit make sure you get one, to avoid over-discharge (this will damage the battery).
Step 2: Wiring Connection
The connection is pretty straight forward and is shown in the diagram above. For those who want to know which wire goes where continue reading others skip to the next step.
First lets start from the Solar panel,
1.Solar panel has a diode on the positive side to prevent the flow of current from the battery to the cell.
2. The Positive and Negative of the solar panel is connected to the N+ and N- of the charge controller respectively.
3. The BAT+ and BAT- is connected to the Lithium Battery's Positive and Negative Respectively.
4. The Battery positive/ BAT+ is connected to a switch and the other pin of the switch is connected to the positive of the Set-up module.
5. The BAT-/ Battery negative is connected to the Set-up module's negative.
6. A resistor of value 47 ohm is soldered on the data pins of the USB output, which helps to charge iPhone phones since they need some signal to activate charging, without this iPhones wouldn't charge.
7. You can add any number of solar panels in parallel to increase the current and thereby charging faster.
8. The micro USB on the charge controller helps to charge the battery by USB outlets.
Step 3: Assembly and Testing
It is self explanatory with the pics. I will try to explain what was done as briefly as possible.
1. First the metal tabs were soldered (that was salvaged from laptop battery) in the middle of a piece of wire , these will act as the lithium battery contacts, which enables the battery to be removed if needed. pics 1 and 2
2. Then made a hole for the wire from solar panel to go into the 18650 box and inserted the two wires(red and black) into the box. pic 3
(In pic 4 I made a mistake by soldering the wire from the tabs to the solar panel, perhaps I was physically present and mentally somewhere else..lol. So it was de-soldered and the wire was cut on one side from the battery tabs.)
3. Hot glued the metal tabs in place after checking the fit with the battery.pic 5
4. Placed the charge controller and step-up module inside the box and marked the places to be cut out. pics 6 and 7
5. Cut out the marked area using side cutters (it was easy to do with it but it did made a crack on the plastic, so use utility knife).
6. After checking the fit, soldered the solar panel wires to the charge controller, battery tab wires to the charge controller, step-up module to the battery with the switch and the 47 ohm resistor to the output USB. pics 8,9 and 10
7. Inserted the battery to test the circuit, by turning on the switch to see if the step-up module powers up. pics 11,12
8. To make the solar panel easy to face the sun, decided to add Velcro to the bottom of the box and solar panel. pic 13, 14 15 and 16.
9. Soldered the solar panel and tested it out the window to see if the charge controller powers up and charges the battery. pic 17.
10. Added another solar panel parallel to the existing on to decrease the charging time. pic 21, 22
Note: I haven't tested it completely, for example how long it takes to charge? I will update those details once I tested it.
Step 4: Modification/ Upgrade
After the built I felt that the positioning of the circuit board interfered with opening and closing of the box and the circuits were not stable (it moved around a lot). Therefore I transferred the contents to another box.
With the soldered Solar panel it was difficult to carry it in pocket therefore I made them removable by using male and female header pins to quickly connect and disconnect.
The best thing about this power bank is it is versatile to charge using USB output from computer or wall charger or using solar panel, plus you can increase the capacity simply by replacing with a higher capacity battery.
Note: You can use this to charge any phone however charging time may
vary depending upon the capacity of the battery and many other factors. You can also attach LEDs to use this power bank as a portable battery as well.
Note: I forgot to add a 18650 protection circuit, since the battery extracted from laptop battery does not have them. So if you are using a battery without protection circuit make sure you get one, to avoid over-discharge (this will damage the battery). Thanks to instructable member brzi420 for pointing it out.
Any suggestions and comments are welcome.
And kindly vote for it, if you like it.