Originally Posted by Davethebluessinger
If you need a bigger power supply for charging multiple cells or at a higher C rate just strip one out of an old PC case, on the power supply it will tell you the colour of the wires connected to the 12V rail and how many amps you can draw off the 12v rail. Just bunch together all of the 12v+ wires and solder them together use those wires and the bunch of Neutral wires to feed your charger. There are a couple of other wires you will have to join together to make the PSU start as they would normally be connected to the switch on the PC. Then cut all of the other wires short bunch and insulate them as they're not needed. There are plenty of tutorials on the net showing what to connect where. It's pretty simple and very cheap! I've been using a 25A supply for 2 years in this way without any problem with a 4 cell charger charging 4 lipos of varying sizes at 1C and 2C rates.
Not completely true. For the most part, what was said above is correct. The parts missing are :
Most PC power supplies require that a load be placed on the 5 volt bus to get good regulation on the 12 and 5 volt bus. Usually, a 5 ohm 10 watt resister on the 5 volt bus will do the job. This resister will get quite warm (hot) so mount it accordingly. You will have to connect one wire (usually the green colored one) to ground to get the supply to turn on. The amount of current you can pull off the 12 volt bus is not the same for all power supplies, some are as low at 5 amperes but most are around 10 amps or a little more. The sticker on the side of the supply will give you the maximum currents you can draw under ideal conditions, one of which is adequate cooling. Keep the vents open and clean and the fan working.