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Convert PC power supply for RC use

The following article is nothing more than a project report. I take no responsibility for how others may use this information. 

I have seen many reports of people using standard pc power supplies to power their chargers, so I thought I would give it a try.
What I used for this project
I used a handful of tools to convert my unit, including a soldering iron, drill, pliers, cutters, multimeter, etc, with no special tools required.

I had an older, retired power supply sitting around the office, so it became my guinea pig. Beyond that, all I needed was some case mount banana plugs and a load resistor, so the project definitely didn't break the bank.

The conversion process
Below are the basic steps I followed to convert my unit and it took me about an hour to complete. 
  1. My power supply (PS from here on out) was safe. I have read about some people being worried about stored energy in the capacitors but my unit had been unplugged for months, so I felt I would be safe. So i removed the 4 screws on the top of the PS to open it. 
  2. I got my bearings and I freed all the wires that leave the PS, laying them out so I see them all and separated out the ones I would need. My power supply used standard color wiring, so I needed
    - the green one for power on
    - a red one for the load resistor
    - several black ones for the ground output
    - several yellow ones 12V output
  3. I then trimmed all the nonessential wires and cut all the wires I wanted to save to about 6-8in long. I made sure to cut nonessential as close to the board as possible to make sure they wouldn't get in the way or cause problems. I capped the few wires I could not cut close to the board with heat shrink tubing. Once done the PS looked much cleaner inside.
  4. Next came the load resistor. I knew I needed about a 1A load on the 5V bus in order to stabilize the 12V bus, and that more was better. I ended up using 2x 1.5ohm 10W in series to create a 3ohm resistor that would draw 5/3A. I made the connections and attached the resistor to the case to keep it out of the way. 
  5. Next came the banana plugs and I had an idea for them. The back side of the PS is made up of a grid of hex shaped holes, so I thought that if I trimmed out just enough to get the plugs to fit, it might be easier than drilling a hole somewhere else. That worked out really well. I then soldered 3x 12V wires to the red one and 3 ground wires to the black one.
  6. Lastly I connected the green (power on) wire to ground. That way when the PS is plugged in and switched on, it will come on.
In conclusion
Once I was finished and had everything tidied up, I replaced the cover and tried it out, and it worked great.

Notes and such
  • I found out that there is a specific order to powering on the PS and charger. The PS must be off when the charger is plugged in or it trips some safety thing in the PS. I then had to unplug it and wait about 30sec before it would come back on again. As long as the charger is plugged into the PS first though, it worked fine.
What I used

Opening up the PS

Getting my bearings

Trimming the wires

Installing the load resistor
I used 2x 1.5ohm 10W resistors
in series for a total of 3ohms

Mounting the banana jacks
This PS allowed me to use some wire cutters to
make the holes for the banana jacks. That
saved me from having to drill the holes.

Connecting the green wire to a ground wire and tidy up

That's it, my converted pc power supply