modify ps power supply to car battery charger

If your supply has a 15V output - that will probably work for a fast charge, but be careful - that is on the high side of charging voltages. If not, forget it - you don't want to go mucking about with an off-line supply like that. There are lethal voltages involved.

What is a PS power supply?? It just strikes me as being "power supply power supply"?? Hows 'bout further information...

Bill

As long as it's a DC power supply and depending on the output amperage.If it's milliamps you will get a trickle charger!

You will need to provide more information on the power supply you are planning to modify, before we can suggest anything. Such as;

Output voltage

Output Current capability

Is output voltage adjustable?

Is output current adjustable?

Tom

sorry for all mine question is I want change old pc power supply to car battery charger

OK, this might be possible to do using the +12V output, if the circuitry of the supply will allow this output to be adjusted up to around +14V. The problem is going to be figuring out which components you need to change to adjust the output up to the needed voltage. If you don't have a circuit schematic, or a very good knowledge of switch-mode power supplies, you are going to have a hard time making the necessary modifications. If you do manage to get the voltage changed to what is needed, you will still need to figure out how to limit the charge current. I think this project might be more trouble than it's worth. Perhaps others here on CR4 may disagree, if so, perhaps they will instruct you further on how to accomplish this.

Tom

OK!! Things now begin to make sense!!

It can be done conceptually, but it could not work very well. The only high current output would be down around 5 volts (on older supplies for 5 volt logic) with secondary outputs say +12 volts at maybe 1 amp, which wouldn't charge a dead battery too well without zapping the supply.

I came across an interesting supply which puts out 25 amps at 13.8 volts at Radio Shack (part number 22-510). This I could use to charge a battery. I got mine at a garage sale for $5.00 so I have no idea what the list price is for it.

I am considering making a 50 amp at 13.8 volt switcher which would run from 90 vac line voltage through 260 vac. This I will do from scratch though. I would not think of converting a PC supply to do the job.

I will encourage you to get a schematic of the supply if possible... and there is gobs of information on power supplies on the internet. It could be a good learning experience for you. Just remember that there are lethal voltages inside. Mine will have as much as 400 volts dc when I rectify the line voltage.

Good luck

Bill