$10 LED Flashlight & Emergency Phone Charger

September is national preparedness month. You can learn more at Ready.Gov.

Communications are a key part of any emergency plan. I'm going to show you how to convert a $10 LED flashlight into an emergency USB charger. The concept is simple and the process is easy using standard DIY tools and cheap parts you probably have on hand.

This would be be great to have on hand when the power goes out or for camping.

The theory is simple. Disassemble a car charger and put it in a flashlight.

For this project you will need:

1 6v "rugged" lantern. $10 at my local Wal-Mart
1 Phone car adapter - conveniently I had a broken one.
1 USB extension cable
1SPST switch - I should have used a smaller one.

Note - this is the $10 LED ruggedized Rayovac. I can't speak to other brands. This one has a 6v to 4D battery adapter that is necessary for this build. It also has a removable handle top with space for wires.

Please bench test your phone adapter on the 6V battery before disassembling it! Not all adapters will accept a 6V input.

Split open the car adapter.

Note the terminals where the power comes in from car. The center pin is the positive and the outside is the negative. Carefully trim these off.

Note where the LED and terminals are. I clipped mine of so I could relocate the power indicator light to the handle.

Note where the USB out + and - are on the board with a marker and trim off the wire that would go to your phone.

Split the wire that was just removed and save it. We'll use it later. I trimmed down about an inch and was able to pull the outer jacket off the wires. Just pull in opposite directions. No need to cut it out with a utility knife.

On Light Prep:

On the rear of the flashlight handle there was a very small Phillips screw. Remove it and put it in a safe location.

Flip the handle top up and remove the screws for the LED light switch.

Trim the excess composite material from the end of the USB cable. Be careful. Removing too much (like I did in the photo shown) will cause the center of the cable to come loose from the housing. Fortunately I had another dollar store cable laying around.

Cut the male end of the USB cable off Drill the flashlight housing in the rear handle area to allow the USB cable with the cable jacket attached to allow to be passed through to the battery compartment.

Now back to the handle - drill a hole in the front for the switch. I should have used a smaller switch but it is what I had on hand.

Drill a hole for the indicator LED that is as big as the end but not bigger than the base of the LED. This will allow you to glue the LED into place.

Drill a hole near the new switch hole into the housing to allow for switch wires and LED wires to pass into the battery housing.

Using a utility knife carefully cut a rectangle slightly smaller than the size of the female USB end. Carefully I made it larger creating a snug fit. Cut this hole as close to the top and end of the handle before the downward curve as possible. This will allow for maximum room for the cable without hitting the light housing.

I drilled 4 small holes in the center of the battery adapter to allow wires to go from the board is located to the spring terminals. There is enough room in the center of the round batteries to allow wires to pass without adding extra width to the adapter.

Assembly:

Power Input: Cut two pieces of 12-18 inch red wire from you scrap.

Solder one end of each to your switch and thread the wire through the hole you drilled in the front.

Thread one end through the battery adapter and secure it under the positive spring. Solder the other wire to the voltage input on the circuit board (Where the 12V + was)

Cut about 18 inches off you USB cable. Use the black and red and solder them to the indicator LED.

Solder these leads to where the LED came off the board. This step is not necessary but I wanted to know when the board was powered on.

Thread the black ground wire through the battery adapter assembly and att Put the handle back on the housing.

USB Cable

Trim the USB cable so it extends a few inches past the . There will be 4 wires. The red goes to USB + and black goes to USB -. Solder those now. Twist the two remaining (green and white or blue and white) wires together with a dab of solder to hold it. You can read more about USB charging standards here - but it will not charge an Apple device quickly.

Since I have an iPhone I'll be making an update to this build soon when I have some additional parts come in.

Place the circuit board under the battery adapter. I put mine in with electrical tape to check the fit. I'll add epoxy later.

Now you have a functioning light with a separate switch for a USB charger!

Final thoughts:

A flush mount USB extension cable in the end would have been easier - but not cheaper.

The LED on this thing is bright! On the batteries that came with it I can clearly see into the top of very tall trees three houses down! This little DIY build hack is great for camping, an emergency grid down power outage or for my for my prepper friends to toss in the bug out bag/vehicle.

This setup uses the standard 5V USB connection to charge my iPhone. It is slow but it does work. I'd like to get 2v on the D+ and D- terminals of the USB. This is the voltage Apple uses to tell the phone to charge faster.

I successfully figure out the pin out using a multi meter from the tiny circuit board on the end of my broken USB adapter. For an iPhone you need to put 2V on the D- and D+ on the USB plug (green and white).

If I had it to do over again for faster charging I'd start with an Apple fast charge compatible car adapter that would allow the 6V input from the lantern battery. If I had one of these I'd remove the case, slim the adapter down and use a male USB plug on the car adapter....sadly my $5 Amazon purchase only works at 12V. So not all adapters are created equal. When I get another cheap one I'll give it a go again.