Introduction: Make a Powerful Rechargable Flashlight Out of a Used Battery (earth Day Part II)

Old lithium ion batteries - many of us have them laying around. And in most cases there is little use for them. Well, until today. In my previous ible and video I showed you how to use them as a powerbank, today I will show you how to turn them into a useful flashlight that lights up your working environment. I also made a project video.

Step 1: What You Will Need

To create your own helpful tool you will need...

• a used lithium ion battery
• a container that fits your battery and the other components
• some wire
• a lithium ion battery protection and charging board
• a circuit board
• a few female pins
• a small switch
• two 3 Ohm resistors
• 24 white SMD LED's (from an LED-strip)

as well as

• a piece of acrylic

To make your work more efficient some tools might be helpful. I recommend using...

• a hot glue gun
• a soldering ion
• a pair of pliers
• a wire cutter

and of course

• a cutting knife

Step 2: Make the Battery Pins

You can use the arduino slots to make two battery pins. Simply rip two metal pieces out and bend them as shown in the pictures. After this you carefully solder them onto a small piece of circuit board so that they have the right distance to fit the pins on your battery. Don't use too much tin, otherwise it will stiffen the pins and therefore make them likely to break.

Step 3: Make the LED Panel

The first thing you need to do is get your SMD LED's. You can purchase them separately but the cheaper way is buying a piece of LED strip and cutting the LED's out of it. That's what I did.

When you have all 24 chips, cut your circuit board to the right size and solder the LED's onto it. I will go with a grid of 5X5 LED's with one missing in the bottom row. They are going to be separated into two groups of 12 LED's in parallel. Each of the groups is connected to the power source through a 3 Ohm resistor.

It is a good idea to pre tin the soldering spots before applying the LED's. Carefully push them down while melting the tin underneath from the sides. As I did not have stripped circuit board for this project I used some garden wire to create negative and positive rails and connected the chip's to it.

When you are finished soldering test the panel using a bench power supply or a few AA batteries. When I first attached it to a power source only half of the LED's where working. It turned out that I had caused two short circuits while soldering and three of the LED's were not working at all (I should probably have tested them before). After I replaced the broken chips and repaired everything it finally worked.

Step 4: Connect the Components and Fit Them Into the Container

Attach wires to all of your components and solder them together. The schematic shows you how to do it right.

I used an old nail container for the housing. Those things are awesome for small electronic projects, that's why I always keep them. Your container should fit your battery as well as the other components. Use a drill to make holes for the switch and the charging port.

When you think that you found a good way to arrange everything, hot glue the parts in place.

Step 5: Create a Tight Battery Compartment

Cut a piece of plastic to the size of the container and make a small hole for the battery pins. Insert it and secure it with hot glue. The only thing that should fit between it and the cover is your battery. Cut out a few more small plastic pieces and use them as spacers so that the battery wont wiggle around.

Step 6: Insert the Battery and See It in Action

The final thing you need to do is insert the battery, close the box and flip the switch. You just turned a seemingly useless old battery into a really helpful little flashlight. You can not really see it in the photos but this small gadget is really bright and if you attach a magnet to the back of it it turns into a great working light for your car. In case the battery is empty another feature comes in handy, it is rechargable. Simply plug your charger in and you are good to go.

I hope this ible was as helpful to you as this little light is to me and that you found another purpose for your old lithium ion batteries. If you didn't already you might consider reading or watching my previous project and maybe you still want to see my current video.


WannaDuino (author)2016-05-01

and I have a question about your schematic,how you calculated the resistance

Becouse I think it is very wrong,you say 5 x in parallel (with 1 of 7 LEDs and 1 of 2 LEDs ( in parallel al the resistors need to bee the same 5"x

In series only 1 resistor (5 LEDs times the voltage devided by current)

In parallel in only 1 row of 5 LEDs ( you need 5 Resistors before each led, of 20Ohm) with 5 volt input

1Rtotal =1*Rtot=1*R1+1*R2'and so on to R5

But you use only 2 resistors before the LEDs

But that's when it is in series, ,I can not see it,and i am not able to come at your 2 times 3 ohm.

led_freak (author)WannaDuino2016-05-01

I know that you would usually use a resistor for every single LED so that if one burns out the voltage won't increase. However I don't think that any of the LED's will burn out in the lifetime of this flashlight and I did not have 24 resistors either so I simply connected 12 LED's in series. This makes 12*0,02A=0,24A of current draw.
The battery has a working Voltage of 3,7 to 4,2V while the datasheet for the SMD LED's states that they work best between 3.0 and 3,3V so I have to get rid of around 0,7V.
So I went with a 3Ohm resistor connected in series with the parrelel group of LED's.
You can also go with 24 seperated 35Ohm resistors. I hope I could clear things up a little bit. If there are more questions left do not hesitate to ask.

WannaDuino (author)led_freak2016-05-01

thanks mate, I Wil look again and recheck,

WannaDuino made it! (author)2016-05-01

this is getting funny friend look,are you my long lasted brother???

Hahahaha,we do exact the same things frisnd

led_freak (author)WannaDuino2016-05-01

Seems like we're thinking the same way. Your next project isn't coincidentally something audio related or is it:D.

WannaDuino (author)led_freak2016-05-01


ALREADY HAVE l my parts,but I am while I was busy, adding more features

Speaker system to Bluetooth,added features radio,module,and blinking LEDs on beats

WannaDuino (author)WannaDuino2016-05-01

I am getting scared now, I Wil ask my mommy if she forgot 1 baby in the hospital,dude. I think this is cool, al the instructables,are thinking almost the same way.we must help each other always. You no what they say!! Mind over power. And a collective over the ones

WannaDuino (author)WannaDuino2016-05-01

I whas testing a few days ago, to do it in series or parallel to make a led bulb or something as you see.but now you gave me an idea for using other pcb boards with copper strips and no dots.thanxxxx

About This Instructable




Bio: Hi, my name is Jan and I am a maker, I love building and creating things and I am also quite good at repairing stuff ... More »
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