Power supply conversion resistor problem.
 

Hey guys, I am trying to increase the voltage out of the 12v rail via 2 1ohm 10 watt resistors in parallel on the 5v rail. Seemed like it worked as intended at first. Raised the volts from 12.3 to 12.9 but they got hot very fast even with no load and shut down the power supply. cut the resistors out and works fine like it did. Anyone know why?

Because you are trying to dissipate 25 watts from each 10 watt resistor. Overloaded.

V^2 / R = power

5V^2 / 1 ohm = 25 watts

Should I try 4 or 6 in paralell? Or go with a couple 10ohm 10 watt resistors?

More 1 ohm jobs in parallel won't help the overload issue. 10 ohm will. Add those in parallel to get the effect you need.

Ok, sounds good. Thanks for your help!

No problem, good luck!

Worked perfect! It did not raise the voltage near as much as the 1ohm 10 watt, but raised it enough to where my dual charger will charge 2 5000 packs at 10 amps each at the same time and the resistors barely get warm.. That's all I was going for. Thanks again for your knowledge.

How's it go.. even a blind squirrel eats once in a while. :lol:

Glad to hear it's working out for you. Thanks for the follow up, always good to get some feedback.