DIY Powerbank for Extremely Cheap





Introduction: DIY Powerbank for Extremely Cheap

Hi! I'm new at Instructables and i want to present my first and simple project: a powerbank for cheap. Sorry for my English, i'm Italian :) Thank you for joining this project! Really Appriciate! :D


Step 1: Step 1: Preparing the Components

The components that you're gonna need are:

-1 9V transistor battery

-1 LM7805 or LM340t-5 Voltage Regulator (this method will not work on iPhones!)

-1 Toggle Switch (whatever you want)

-1 5mm LED (any colour will work)

-1 1kOhm resistor (possibly small dimensions)

-1 USB Female Port (Extract from any broken USB object!)

-1 9V Battery clip (Extract one from a dead 9V battery)

-Wire, (30AWG will work just fine)

Step 2: Step 2: Prepare Your Instruments

That's the instruments that's you're gonna need:

-Soldering Iron (Preferible with controlled temperature)

-Lead Solder (60/40 Rosin Core)

-Pliers (so you're not going to burn while holding wires)


-Helping Hands plus Magnifying Glass

Step 3: Step 3: Connect Everything As Described (see the Pic for Reference)

step 1: connect the positive of the 9v clip to the left pin of the LM7805 (facing up)

step 2: connect the negative of the 9v clip to the middle pin of the LM7805

step 3: connect a piece of wire to the right pin of the LM7805 (it's the 5V rail)

step 4: connect a piece of wire to the middle pin of the LM7805 (it's the negative of the 5V)

step 5: interrupt the 9V line and put the toggle switch between the +9V from the battery and the +9V of the regulator

step 6: connect an LED to the +5V and common ground

step 7: solder the USB female according to the scheme (short the two data lines)

step 8: pack everything in a container

Step 4: Step 4: Encasing Everything in a Case

i just add mine in a old broken powerbank case, perfect fit! you can use a plastic box or a small project box. Mine is a mess, but it counts the estetic :) Now Flick the Switch! if everything works, the little LED light should light up. if not, doublecheck the connections.

Step 5: Step 5: Test Everything Before Trying on the Real Thing

Before trying to charge the phone, check the voltage and the amps with a multimeter. The specs are:

Voltage: about 4.91 to 5.01volts

Current: about 500 to 700mA (mine is 380mA because the battery is low on charge)

Also test with a cheap USB thing, like a LED light or a really old phone. i'm testing with an USB scale

Step 6: Step 6: ENJOY!

Thanks a lot for following my projects, you guys are awesome!



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    27 Discussions

    This is going to produce more heat than energy.

    This is such a bad idea, I would not plug into a phone. There are modules for this on aliexpress for about $2 and they have protection built onto the circuit.

    6 replies

    hi! this powerbank was maded only for emergencies, not intended to be used as a powerbank to charge complitely the phone battery. if you want to go efficient and safe, buy from eBay a small powerbank kit for 1.25$, the battery is a 18560. you can find these in a computer battery or electronic e-cigs. have a nice day!

    It's a 3.6V battery that won't work with your 7805 which needs at least 6.5V to its entrance.

    What is a 3.6 volt battery? The instructions use a 9 volt battery. perhaps you're referring to the 18650 battery mentioned in the author's comment? If so, if you read the comment carefully, you will see that he is not suggesting that the 18650 could be used in this circuit, but merely stating that some commercial chargers use such a battery.

    I applaud your efforts but this is not a good instructable. It's not a matter of being afraid to make this device, it's that you are giving people very bad advice. Once I was hard up and bastardised a car charger to run off a 3s lipo. There are smarter ways to make a power bank.

    There's no need to be rude. It's not bad advice at all. I won't say that this is a particularly efficient charger, nor will it give much of a charge to any modern device, but it is quite safe. So long as the connections are made correctly, something you must always be careful with in electronics, this will charge any USB device without worry. Modern devices may 'reject' it and refuse to charge, though in reality they still charge, just very slowly.

    Actually, this powebank is intended to be used where no energy sources aren't avaible. Not for all-day usage.

    Given the dire warning at the beginning and the shaky knowledge throughout I think would be wise to forgo this emergency only battery pack and spend a few bucks on a real one for you know that resistors and stuff are correct and are not going to damage your thousand-dollar phone

    It is not a good idea to connect the led directly to 5 volts

    Requires a resistance of 150 ohm connected in serie

    I think

    5 replies

    Actually, if you look really close (i didn't put to the scheme, sorry) there is a 1kohm resistor

    You should at least give reason for not connecting 5 V Directly. What may happen if done so?

    Green led normally are 2,2 volts and 20 to 30 mA
    If you want to connect to 5 Volts you have to put a resistor in serie
    You can use a online " Current Limiting Resistor Calculator for Leds":

    The Led will burn. A green Led has a forward (zener) voltage of 2V, if there's no resistor, it will absorb the rest. So, the battery will be empty faster and the Led dissipates heat for nothing. The regulator will heat as well. In fact this is a very bad way to build a powerbank.

    Look at the LED in the first image of step 4. there is a resistor there. it's hard to see, but it's there. I'd go for either a 220Ω resistor or a 330Ω resistor for 5v

    I make a list for you:
    The 9v battery is 1€
    The lm340t-5 is about 1€
    The led is about 0.25€
    The resistor is 0.15€
    The switch is 1.25€
    The USB port is free
    The wires are free
    Total price: 3.75€


    1 year ago

    One thing I would point out to you; in your schematic there is no resistor on the LED, but in your actual circuit there is one. I would suggest updating your schematic to avoid the rather aggressive comments of those with less patience for beginners.

    1 reply

    Thanks for the tip! I didn't notice that!

    Very simple idea! How long does it take to charge your phone?