Simple 9v Battery Case Flashlight

In this Instructable, I'm going to show you how to make a simple LED flashlight using a 9v battery case and a small LED. It's extremely simple and quick to make. It only uses two parts (other than the 9v battery itself). Since it uses so little power, it also has a very long battery life.

Components:

9V battery case with switch

9V-12V 3mm LED (they come in large packs)

9V battery

*if you don't have it and don't want to buy these LEDs, you can use a typical voltage 3mm led, but you'll have to add in a resistor in series (300-500 ohms). With the resistor, it might be hard to fit everything in though, so I strongly recommend a 9-12v 3mm LED.

Tools:

scraper tool, spudger, chisel, etc - prying tool

Soldering iron - if you don't have it, you'll have to twist the wires together.

Wire stripper (scissors OK but not ideal)

Scissors, wire cutter, some cutting tool

Slide the top cover of the battery case off. The cover is on the side of the battery case without the switch.

*note: my battery case in these images is a bit dirty because I used it for another project before. yours will have longer wires than the one in the pictures.

Use a prying tool to open up the inner cover at the top of the battery case. Don't try to grab it by the notch where the screw would go in - that's not connected to the inner cover. Taking off the inner cover should reveal a switch with some wires.

First, cut off the wires until there's only a bit more than half an inch (1.2-1.5cm) of wire sticking out. Then, strip around a quarter-inch (0.5-0.7cm) of wire so that the conductor is exposed. If you don't have a soldering iron and will instead twist the wires to make connections, strip more, closer to 3/8 in (~1cm).

Trim the LED to around half an inch (1-1.5cm) long, depending on how much you want the LED to stick out of the case in the flashlight. Make sure that the long lead stays longer when you trim it so you don't get confused about the polarity.

Bend the negative lead of the LED (the shorter one) outwards to the side at a 90° angle. In the picture, it's bent immediately at the bulb, although you may want to leave around 1/8 inch (~1mm) of space before it's bent so that the bulb sticks out more out of the case. If you bend it immediately as shown in the picture, the bulb won't stick out that much of out of the case.

Solder the negative wire of the battery case to the negative lead of the LED (90° bent lead). If you don't have a soldering iron, twist the wires together.

You don't have to apply heat shrink tubing, just make sure that the exposed wire doesn't touch.

Solder the positive wire of the battery case to the positive lead of the LED (unbent lead), similar to the previous step.

Put the soldered LED into the battery case. The LED should be oriented so the unbent lead (+) is inserted on the right side of the screw notch, as shown in the picture. You may have to bend some of the wires to make it fit. The LED bulb should fit in the hole where the wires used to go.

Carefully put the inner cover back on. Make sure you align the holes and columns. You may have to move some wires a bit so that no wires obstruct the case attachment columns.

Put in a 9V battery (make sure it has charge in it) by inserting it in the large case compartment, then pushing it up. Make sure the polarity is correct (it'll not snap if not).

Then, slide the case cover lid back on, and you're done!