Computer Power supply as shop supply?

[(unknown)]

I have an old 450 watt PSU from a computer that specs at 14 amp on the +12 volt line.  I want to use it to power some battery chargers.  I ground the green wire to turn on the supply, and hooked the yellow +12 and ground to the charger, (which draws 2 amp), but the PSU won't handle it.  My charger reports low voltage, (it drops to 10.5 volts as the charger ramps up).  I don't understand why this would be?  I tried two different supplies and they both act the same.

Thanks in advance!

ERic

[TomW]

Air;

First thing wrong, if I understand you, is that a regulated 12 volt source will be pretty useless to charge 12 volt batteries that need nearer 14 volts for full charge.

I do not understand your reference to a "charger"? Do you mean a charge controller? If so the situation gets worse as the controller will drop that 12 volts some, also.

We need more information to help in any meaningful way.

Cheers.

TomW

[mungewell]

Hi,

You might find that the supply is primarly regulated from the draw on the +5V rail, and the other supplies are just a 'freebie'.

Try loading up the +5V rail at the same time and see if the +12V is any stronger.

Simon.

[gizmo]

This site has some usefull info.

http://www.wikihow.com/Convert-a-Computer-ATX-Power-Supply-to-a-Lab-Power-Supply

I've also modified a few AT PS's to drive my CNC router, tricked the output up to 14 volts, and connected two PS's in series to give 28 volts at over 6 amps, works great. Need to remember to isolate the -ve on the high side PS.

Glenn

[stephent]

"Most" regulator/controller/chargers need at least 1.5 volts or so input above their output to be able to regulate properly.....and loading up the +5 volt rail with a couple of ohms resistor is a good idea to get the PC PS into regulation good too--as was stated before.

[(unknown)]

The 5 volt line almost always has to be loaded to regulate the rest of the outputs.

[Opera House]

To make this a little clearer, the power supply has no feedback from the 12V output.  It doesn't even know it is loaded.  Only the 5V is regulated.  You can switch the sense line to the 12V.