Build a Power Bank in $2





Introduction: Build a Power Bank in $2

Hey! everyone My name is Steve.

Today I'm going to show you How to make a Power Bank in just $2 not believing?

Follow me and you'll get it

Click Here to See The Video

Let's Start

Step 1: Features

Power Input

  • 5v 2A via a micro USB

Power Output

  • 5v 1A And 5v 2A Dual USB


  • It depends on how much battery you added

Safety Features

  • Short Circuit Protection
  • Over Voltage Protection
  • Over Charge Protection
  • Over Discharge Protection

Step 2: Things You Need




    Suggested Buy

    • 18650 Battery - Click
    • Vichy VC99 Multimeter - Click

    Step 3: Where to Get Free 18650 Batteries

    I used my old laptop battery to get the cells check the video down below

    Click Here to See The Video

    Step 4: How to Check How Much Capacity Is Left

    I used a Battery Capacity tester to check the real capacity check the video down below

    Click Here to See The Video

    Step 5: Assembling Part 1

    • I used 18650 battery holder to hold the 6 battery that I salvaged from an Old laptop battery
    • After that, i used a thick wire to solder all the 18650 in parallel configuration

    Step 6: Assembling Part 2

    • I used dual sided tape to stick the battery and the Board to the Acrylic sheet

    Step 7: Completing

    • And then I soldered the 2 wire to the board ( see the image )

    : Notice - Please be careful about the polarity

    Click Here to See The Video

    You Just Made It

    Now just Plug the power and enjoy

    Thank you for visiting my Instructables Stay tuned for next Projects

    2 People Made This Project!


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    We have a be nice policy.
    Please be positive and constructive.




    The batteries already have tabs welded to them---when you disassemble the packs, just cut the tabs in the middle. This will result in tabs hanging off with the sufficient length that soldering to them will not heat the battery enough to cause damage.

    On the other hand, soldering directly to battery end-buttons is liable to transfer enough heat to melt the plastic between and around the internal electrodes, which could lead to catastrophic shorts and spectacular failures. Similar damage was causing the Samsung Note battery fires last year.

    Another issue: LiIon batteries are more voltage-sensitive than other batteries.. They should not be paralleled---especially if cells have different histories. I haven't seen many commercial packs that have more than 2 cells in parallel, and they use fresh/new cells. The safe way is to put cells in series, and have individual balancing connections going between stages. It's trickier and more expensive but most chargers support that.

    You are correct on the soldering, but you are reversed on the parallel vs. series idea. The key with Li-Ion is to not let them get out of their voltage range which is 3.0 to 4.2V on the outside. They will last longer if you avoid those extremes. Running in parallel guarantees that all the batteries charge and discharge evenly as they are forced to balance one another. Running in 2S, this means 6-8.4V, but it allows the extreme possibility at full discharge 6V for one to still be at say 4V and the other to drop to 2V or anything else that adds to 6V. Obviously the more cells in series the more possibility for imbalance.

    You're right that one can't let the Lithium batteries get out of the narrow voltage range---that's why Li charger systems are tricky and can't just be a 'diode and lightbulb' circuit from the lead-acid era. The Li chargers measure individual battery voltage by having individual 'balancing' connections to each level of the serial stack.
    The problem with the parallel setup is this: the Li cells have small internal resistance and narrow voltage tolerance. Small cell differences result in huge balancing currents. Healthy cells that don't differ much will, as you say, just balance out their charged state, but if a cell goes out of spec, at best you just waste the charge out of the good cell, and at worst you can burn up the bad cell with the excessive current flowing from the good ones. Yes you can mitigate that by having balancing resistors and/or fuses on each battery, but why bother f you can just throw a series stack balancing charger on the problem? In either case, you need some sort of monitoring circuit because as you say, you can't let the Li battery charge/discharge out of its design voltage window.
    Simply saying, the Li battery chemistry is much less forgiving than the lead acid, so you need fancy charger, and series stack is just easier to handle.

    I know about the Li charging as I just got delivery of my new SkyRC Imax B6, :-) and I was with you on charging but Jehu Garcia disagrees. He stated clearly that you can basically trickle charge Li-IOn batteries, as the current will drop to zero as the voltage matches the charging voltage and he has been doing it on his van for two years. I am not saying it is ideal, but it works. It is also probably crazy slow. I also agree that if one of the batteries is REALLY bad then a parallel setup can go south, but I will stand by my original claim, and double down due to the slow charging speed of the battery pack here, the parallel layout is generally safer. Even if we look at real lemon cells, they are much more likely to go south in series then parallel as balancing circuits are not foolproof and can only handle minimal charging differentials between cells. If those limits are exceeded then the balancing circuits will fail and you may not even know that they have failed. This I got from one of the electric bike channels who came out as anti-BMS and pro active monitoring. In the end I think we can both agree the key thing is filter out the real lemons as they will get you in any configuration.

    Ok, I usually don't comment on many things, but the hat full of A-holes complaining, kill me. $2 is very feasible IF all you need to buy is a board. I have everything listed but the board and it would cost me $2.01 as of today's date.

    And for the people talking garbage about soldering batteries, have YOU ever witnessed such an explosion or fire with your own eyes? I have not seen Lithium Ion batteries do anything but just die.

    I am an electrician with nearly 20 years of industrial, commercial, residential experience. I have been there and done that with "low voltage" and "mains voltage". Simply put anything on the customer side of the power companies transformers. I have been in live switch gears working when they could not be turned off. The reason I list my experience is this, when you're at the level of game in the I.B.E.W. you take classes. More than I care to think about. Some deal with nothing but different kinds of terminations. It all boils down to installing components as the manufacturer says to.

    I admit I have not read any li-ion manufacturers literature that says that their cells cannot have a hard connection to them via a solder joint/connection.

    If you think about it, why would manufacturers weld tabs instead of soldering wire to them? It is all about speed and economy. I am also going to add, I have rebuilt several battery power tool packs with new lithium cells and have yet to have anything go wrong with any of them.

    And why do people want to criticize others so badly? It was not long ago in the US that everything was built to last or be repaired and continue to provide service/use. Now days everything is made to be disposable. Some folks in these "3rd world countries" have less than others and make due with what they have available. Look at Cuba. For decades they could not get parts for vehicles or most anything for that matter, and the level of ingenuity those folks have is astounding and inspiring.

    The welding is also about not transferring heat into the cell. You are correct that a good solderer will "probably" not impart enough heat to damage a cell, but a rookie might. From what I have seen, lots of people solder their cells and they are fine, but the key is to cut down on the heat transfer. Sorry that people are crazy. I've just accepted that fact and move on. Good Instructable.

    Your post make lot of sense, hats off for your experience.

    Actual cost is $41.96, not the $2 advertised.

    Connecting batteries of different capacities in parallel is just begging for them to catch on fire.

    Too many things wrong with the to even start to make a usefull commment!

    Would appreciate a 'useful comment' on key areas that you think are wrong.