PC Power Supply repost

[srnoth]

Note to whoever deleted this:

Please tell me why my post was deleted. I posted it in the right section (controls), and I am thinking of a way to power 12v appliances, while the battery is charging, there by allowing the battery to charge more quickly, taking the extra load off the charger. Does this not have to do with RE controls? It could be usefull for someone charging their battery bank off a 120v generator. Anyway, if whoever deleted this really has a problem with this topic, please atleast explain.

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Hey there folks,

I just got a Dell P4 power supply for free, and the label on it says 14amps at 12v, which is a nice amount of power. I connected it to a 60w bulb and it lit it up no problem. Anyway, I was wondering if I could use this as a battery charger, and adjust the voltage to 13.7v instead of the 11.6v its putting out now.

I have a feeling it will not work as a charger, because I think (not sure) that the way these power supplies work is that they try to reach the set voltage, and if they cannot, they simply shut down.

But, even if I can't use it as a charger, I was wondering if I could use it to power 12v appliances (bulbs, car amps etc) while charging the battery with a regular charger. Basically, if I can change the output voltage to 13.7v, and use diodes so that the items only run off the battery if the battery voltage is greater than the power supply voltage. So power can come from the battery to the power supply and appliances but not the other way round.

So, I guess my question is, can the voltage be changed?

Thanks for your help,

Stephen.

[Nando]

Stephen:

The supply may be used to charge a battery, all depends of the type it is, unhappily I am not familiar with it.

Most of the power supplies now, do have current protection so the battery can be charged with the battery, it will behave as a constant current supply until the voltage of the battery reaches the setting of the power supply.

Some supplies may have a small adjusting trim potentiometer to adjust the output, and if not, one needs to discover the resistors that set the output voltage to adjust them to your new voltage settings.

There is one that goes from ground to a pin of the controlling I.C. and from there one or more resistors in series to connect to the output voltage.

To increase the one from the pin of the I.C. to the output voltage or reduce the resistor from this famous pin of the I.C. to ground -- ideally it is best to increase the upper resistor to the output voltage --than reducing the lower resistor BUT the change of the output voltage is low.

So one can change either resistor, the lower one is probably the best in this case to parallel a resistor to the one going to ground.

Do you have a voltmeter ?.

To read voltages to determine the change?.

let me know

Nando

[veewee77]

Those power supplies are generally set to put out the 5v supply and the rest of them are pretty much along for the ride.  If you only load the 12V outut, that thing won't live very long. The extra circuits are by-products of the extremely clean 5V supply and it must be loaded properly for the rest of it to work correctly.

Doug