# PSU / Combine 12v and -12v rails for 24v?

1. May 1, 2010

### singlespeed

I would like to increase my voltage on these PSU's to 24v. If I combine the -12v and +12v for 24v do I still get the high current of the 12v side?

+12v 70A

-12v .8A

24v... but what is the current potential?

2. May 1, 2010

### uart

No you don't.

You must still respect the -12V side's current rating which is typically only half an Amp or similar, so that will set your overall current rating for 24V operation. Note that you also require a floating (non ground referenced) load for it to work, this part is very important!

3. May 3, 2010

### singlespeed

Thanks for the reply, I figured it would inherit the lower amp side. Is there any way I can boost the current voltage to above 12? I'd like to see it slightly higher in the 14-16v range.

4. May 3, 2010

### MATLABdude

ASSUMING the outputs are floating and completely independent, you may be able to put the power supplies in series (as you would with two 12V batteries). You should be able to use a mutlimeter (with the supplies turned on) to see what the voltage is between one supply's 12V supply, and the ground (or 12V output) of the other. If it's anything but open circuit, then a connection exists between the two of them.

Unfortunately, I suspect all of these will have the ground output tied to case and the ground prong on the plug, and hence be connected through the ground line, and you won't be able to do what I suggest above. A decent (current-limiting, short circuit protecting, etc.) adjustable two-channel power supply (up to 30V) will only run you around $150-$300 new, and possibly less somewhere like eBay. However, most of these will only supply 3 or 5A max, per channel (though you can connect them in series to get up to 60V, or put them in parallel to get 6 or 10A).

EDIT: Finished dangling thought