Solar Power Bank With Salvaged 18650




Introduction: Solar Power Bank With Salvaged 18650

About: I'm a graduate of Aircraft Engineering Technology (Hons) in Mechanical. I am passionate about energy, electric vehicles, gadgets, tools. My projects basically reflects my needs.

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

4. Wires

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,

Tools needed:

1. Soldering Iron

2. Utility Knife or side cutter

3. Marker

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 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.

5 People Made This Project!


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175 Discussions

the micro usb you have linked to is different to the one you have used as the one in the link has a protection circuit aswell as the charge circuit, it connects to the battery and then the board can be wired up to whatever you want the single 18650 to connect to

4 replies

Well thats great, I bought mine about a year ago and did not have any protection circuit, so this one is much better thanks for pointing it out.
I am glad that you found this useful..

definitely useful, inspired me to do this (see pics below) but as I only had the charge circuit and 5v boost up available I used a battery with built in protection but will be doing another couple with the batteries I found in my mum's "dead" laptop battery which had a damaged contacts so lucky me lol


Nice built...... Post your other built pics too when you are done...
Yeah better to recycle those perfect cells than throw them away.

glad I read this as was planning on just making it didn't even think of a protection circuit lol

cheers for the info!!

keep on making!!!

Hi. Can you make a DIY 5 18650 battery solar power bank with dual usb output (2a and 1a). I'm confused with what parts should I prepare. Thank you.

1 reply

DC to DC converter has a max 600mA output. Most modern android phones need at least 700mA to charge. This will not work

1 reply

1 year ago

hey there...amorarun.? i know how much time will it take to completely charge a 5000/10000 mAH power bank ?

Bro plzz tell me..I have 4 battries each battery have 4.8V DC power..Can I use my 4 batteries at a time..Is there any problem for my circuit?? reply me fast frnds

2 replies

You can do that but the charging circuit mentioned in this Instructables is designed to charge only one battery. The problem with using more than one battery in parallel with this circuit is that it can't balance the cells. This can lead to uneven charge and might damage the cells in the long run. Do Google about charging lithium ion batteries and you will get loads of info.

I'm not much of an expert about lithium batteries, I'm still learning. I could be wrong.

When the cells are connected in parallel, they are always balanced, because the voltage for all points that are connected is the same.

The only difference when connecting more cells in parallel is that there is more capacity to charge, so you either need a larger charging current, or it would take longer to fully charge the battery pack. It is true that the correct charging current will extend your battery life, but it's far from critical. Also, I don't even expect that you will achieve the ideal charging current for a single 18650 cell from a small solar cell. BTW always better to have a smaller than ideal charging current than a current that's too large. A low charging current can decrease the battery life a bit, but too high of a charging current might end the battery life instantly, with fire... :)

When you want a higher voltage power bank and start connecting the battery cells in series, that's when you need to start thinking about balancing the voltages.

Anyways, just trying to educate (maybe you already learned this as the I'ble is already a year old). I really like your project and I'll soon be making my own so that I can charge up my digital camera's battery from the power bank after a day of hiking in the sun.

if I want to upgrade this by adding 10 w solar panel and much battery then what changes should I do ?


2 years ago

Suppose I use 2pcs. of the 18650 Li-ion batteries what adjustments do I need to the parts e.g., solar panel, charge controller, etc. In other words to the whole circuitry. I have just a little background in electronics just enough for me to understand how to read circuits but not to compute the ratings of the parts required. TIA for any advice anyone could extend to help me. :)

guys its not working plzz any one help me..

Bro plzz tell me..I have 4 battries each battery have 4.8V DC power..Can I use my 4 batteries at a time..Is there any problem for my circuit?? reply me fast frnds

Boss i have doubt.i have 4 laptop batteries each battery 4.5 doubt is can give 4 batteries at a time? it working or not?? circuit is damage or not?

Hi sir. I made it but it seems in the beginning that it cannot charge without power supply from the charger. Will it charge without power supply? Please help!

Can I use any other value resistor other than 47 ohm? Please reply fast.