Built ATX PSU to Multi-Volt power supply. Voltage drops when applying load, what may be wrong? Answered
I converted my 500w PSU following instructions in here. The PSU boasts 480w real power on with 20amps on the 12v rail. I thought I had done everything correctly, and the Power supply gives correct voltage on all binding posts when there is no load, but when I connect a simple 5w lightbulb to the 12v the fan spins down and the light is not as bright as I would expect. Also when measuring the output voltage it now is down to 8,30 volts. Measuring the amp shows 0,33A. When trying out a 21w lightbulb the problem gets more visible, as the light flickers and there is a ticking sound from the PSU. The voltage now travels between 8,10 and 8,16 volts, the amp showing 1,31 amps.
I tried grounding directly to the PSU chassis, I cut the wires to the 5v USB ports (these did not work anyway, perhaps because I have no sandbar resistor?) and also tried to give power from the wires only related to the 24 PIN molex connector or only from the 4 pin connectors, all with the same symptoms. Anyone have any clue as to what may cause this anomaly?
My plan was to use the power supply as a substitute for a battery to run power in my caravan, converting straight from the 220v. There are only a set of lights and a small water pump running on the circuit, adding up to approximately 200 watts if everything is turned on. I figured the PSU would be sufficient to do this, but maybe I am mistaken?