How do you use a PC power supply?

[NeoPantera]

I need an inexpensive 12V source for charging 3S. I have an old PC power supply, but I don't know how to make it work for this purpose. Would someone please give instructions?

[Motions]

http://web2.murraystate.edu/andy.batts/ps/POWERSUPPLY.HTM

[catfight]

Neopantera,

I just bought a PC power supply from Frys.com and with rebate it is $0. Costs $40 + $8 shipping (really fast shipping to me anyway) so net cost will be $8. It is rated at 500 watts and 12.3 volt output is rated at 28 amps! Got it last night. Went to Radio Shack and purchased 8 ohm 20 watt resistor and hooked it across one red wire and one black wire (presents load so it does not cut off). Tied the green wire to another black wire (to allow the PS to turn on). Took the 2 long 12 volt only connectors (yellow wires are 12v) and the black wires from those same conenctors - soldered all 6 yellows together and connectod to my charger + input, and all 6 black wires together to the - on the charger.

Cut all remaining wires short and heat-shrinked them in bundles by color (prevents shorting out).

I now have a 12 v 28 amp power supply. Comes with power cord and builtin on/off switch. I tie-wrapped the resistor in front of the fan for cooling. Done :D Took about an hour. Rebate takes 8 to 10 weeks....

[NeoPantera]

thanks. both are excellent suggestions. The link from Motions worked great. I now have a 12V sourse from an old computer that was just sitting around.