Cheap Power Supplies for Battery Chargers

When you get into flying and driving RCs, things tend to get expensive. Because of this, I'm always looking for a cheaper way to do things, which is why Flite Test is so awesome.

When i got started in RC flying, I ordered the cheapest power supply i could find for my battery charger. When i tried to charge 4 cell batteries, it would overload the power supply. So i had to charge my 4 cells slowly. I decided to do something about it.

This tutorial is really only cost effective if you have a computer that you're getting rid of, or have access to junk computers. Watch out for your local dumpster day!

WARNING! Computer power supply units have massive, very powerful capacitors inside of them. They can give a pretty nasty shock if you are not careful. This should not be attempted by anyone who doesn't have a basic knowledge of electronics. If you have any concerns or questions, ask them below BEFORE you open up your PSU. Now, lets get started!

Materials that you need:

• PSU out of a computer
• XT-60 Panel Mount Kit
• SPST Switch (optional)
• Power Cable for PSU
• Small breadboard (optional)

Tools/supplies that you need:

• Soldering iron
• Solder
• Flux
• Wire cutters
• Wire strippers
• Medium/thin CA
• Phillips screwdriver
• Drill with large bit
• Dremel
• Multimeter/voltmeter

First thing you need to do is make sure that you have enough output power on the 12 volt rail. On this power supply, i have 18 amps, which is plenty for my battery charger.

Now, you need to know which color wires go with each power rail. One color wire corresponds with each voltage. The most common color for +12 volts is yellow. Black is always ground. If you aren't sure, you can turn on your power supply, and check each wire color with a multimeter. To turn on the power supply, you have to find the Brown wire, and connect it to a ground (Black) wire. Now you can check each wire color's voltage. You can cut all of the connectors off of your unit at this time, but leave enough wire to work with. You can always make it shorter later.

Once you know each voltage, write them down, and start taking the case off of your unit, keeping track of all the screws. Unscrew the fan from the case at this time also.

Cut all the zip ties that hold the wires in place inside the unit.

Unplug your fan from the unit, and take it out of the case. Then, remove the power wire from its track. We are relocating the fan to the outside of the case, just to make more room.

Route the power wire through the fan grill so that it won't be pinched anywhere when you re-attach the fan.

Plug the fan back into its connector, as seen here.

Make sure the connector isn't going to pull off of its pins.

Now screw the fan back onto the case from the inside.

Next, untangle the wires and sort them by color. Notice the group of different color wires on the right. The only wire we need from this group is the power wire, which is brown.

We only need the Yellow, Black, and Brown wires. Cut all of the other wires as short as you can, making sure the bare end isn't going to touch the side of your case, or any other components on the board.

Now lets move to the switch. I'm using a lit SPST switch. It works the same as a normal SPST switch, but when its on, it lights up. I used one of my +12v wires to power the light on the switch.

Take measurements of your switch, and mark out a spot where there is plenty of room on the inside of the case for wiring. You don't want components touching each other inside the case.

Test fit your switch before you start soldering!! It will save you time in the long run.

Run a ground wire and your brown wire through the hole. The yellow wire is for the light on my switch. Put shrink tubing on your wires at this step if you prefer.

Solder the wires onto the terminals of the switch. I chose to skip the shrink tubing, since it was in an enclosed, grounded case.

Insert your switch into its mounting hole.

Now its time to start soldering. In order to get as much amperage as advertised from your PSU, you need to combine all off the ground and +12v wires. You need to combine all of the +12v wires and all of the ground wires to get the maximum amprage possible from you unit. For the ground, since there is about 15 wires, i like to use a breadboard. Put all of your ground wires together and solder them into one large connection. If you chose to skip the breadboard, simply solder all of the ground wires together.

Do the same wit the yellow wires, but without the bread board. Then, add some wire to each solder lug so that you can connect it to a plug later. (That solder lug for the ground looks horrible!)

Cut your breadboard off so its as small as possible. (An even closer look at that ugly solder lug! Eww.)

Wrap both the breadboard piece and the +12v wires with electrical tape. Make sure all of the bare metal is covered.

Now we can move on to the panel mount. Find a drill bit the same size as the panel mount. I used a step bit.

Drill your hole, and make sure its clean of any burs.

Test fit your mount. If it fits, use a marker to mark the 3 holes around the mount.

Drill these 3 holes for the mounting bolts.

Using a dab of medium or thin CA, glue the 3 nuts into the back side of the mount. This makes installing the bolts much easier later.

Thread the wires through the back connector and solder on you ground and +12v wires. If you want to use shrink tubing, put it on before this step. As you can tell, i again, chose to skip the shrink tubing.

Thread your connector through the mounting hole. Line the back mount up with the mounting bolt holes.

Mount the connector into the panel mount using the included grub screws.Try and make sure the connector is level with the edge of the mount for a neat look.

Install the bolts using your screwdriver. (Aww man, my connector is crooked...oh well)

And youre done! Put the cover back on and test your unit. When you turn your switch on, your fan should spin up. If the fan does not come on, and you get no power from your XT60, you may have:

• Used the wrong wire for the power wire on your switch

• caused a short somewhere in the circuit

• used a PSU that didn't work to begin with (there was a reason they were getting rid of that computer. haha.)

Go back and retrace your work if it does not turn on properly.

Use your multimeter to check and make sure you have +12 volts coming out of your connector. (I had my probes connected to the plug backwards, which is why it shows negative.)

Connect up your charger and start charging! Thanks for reading! Please let me know what you think. If you have any questions, please leave them in the comments below and i will do my best to answer them! Keep on flying guys!

If you're on Facebook, check out this awesome group that I am a part of. Its called Flitetest Fan Swapables. We hang out, bounce ideas and questions off of each other, and post about our builds. Anyone is welcome! https://www.facebook.com/groups/1418914708327072/

See you there!

Sherman H.