How much voltage can I get out?

[icecoolwas]

ok so let me explain. I have a 750w computer powersupply that gives out 60A @ 12v continious. I have modded it so it turns on without a PC Motherboard and have bundled together all 12v wires and all 12v- into cables, there is a senseline coming from the 12v mobo connector which I am intended to use to mod my psu 12v rail voltage. I found this diagram on the internet which shows me how to do it.



Since I am no good with eletrical designs etc I was wondering if that modification will work in my scenario and if so, what would the maximum amount of voltage I could be able to get out of my PSU without damaging it (approx?) I want to get like 13.8v but I am sure that is not possible, but how close would you go? I dont want to damage this powersupply. it does have overvoltage protection also.

Thanks. (Sorry if this thread is in the wrong section, I thought it suited it well if it is in the wrong place).

[godfrey]

I haven't tried, but would expect to get 13.8V easily - it's only 15% extra.

I don't think your diagram is correct, though. Shouldn't the red wire from the right side of the pot be connected to the other end of the 68 ohm resistor?

Perhaps a smaller pot could be used e.g. 1K or 2.2K? With 10K, all the action will be right near one end and it will be difficult to adjust accurately.

It might also be a good idea to connect a resistor in series with the pot as "stupid-proofing" to limit the maximum voltage. 150 or 220 ohms should limit the voltage to about 17.4V or 15.7V respectively.

btw: Computer PSUs can only deliver high current on the +12V rail. The -12V rail is normally rated much lower.

[fredy2]

I have yet to see an ATX power supply that will provide 60 amps at 12 volts.

[icecoolwas]

Originally Posted by fredy2

I have yet to see an ATX power supply that will provide 60 amps at 12 volts.

Theres quite a few.

take a look at the corsair tx750

or the one ive got, oryxx 750W.

[icecoolwas]

finally got my lazy *** up (yeah I know its been ages) and I'm getting down to doing this now.

godfrey I took your advice and ordered a 5K Pot and yeah I guess that diagram is wrong, so basically all I have to do is apply some resistance between the senseline and the ground right? I'll use a multimeter to make sure I start from the correct side, increasing resistance from non, at the wanted output I'll apply a small load, and adjust abit more, then just hotglue the pot from any other further adjustments.

[star882]

A friend of mine is modifying a 550W ATX power supply to output 10-15v at up to 35A, with adjustable current limit and output voltage. Its initial purpose is to float charge lead acid batteries in a home network rack, but the wide output adjustment and adjustable current limit make it easily adaptable for new lithium batteries.

[raquel2010]

I never try this before that is why I am not more familiarized with this thing.

[icecoolwas]

anyone know if I really need the 68ohm resistor? Can I just do this with a 5k preset pot? I'll be using a DMM to make sure I dont apply wayy to much resistance by starting at the wrong end, and once i get it to 13.8v, I don't think it'll be easy accidently knocking a preset pot.

thanks.

[es44]

Frankly, i really think you should get someone skilled to look at that schematic once more. There's (at least one) serious error, as the +12v is clamped directly to ground in the top right corner.
I'm not really shure about the 68r, i think it needs to be there to assure the pot doesn't go to zero ohms. That will still make a direct short if you avoid the 68r.
Don't use it as is, you'll end up with fireworks.

Best regards
Ebbe

[icecoolwas]

just had another look at my PSU, and I found something really interesting, theres two senselines, one for the ground and one for the 12v... doesnt make sense, I believe I have to apply some resistance between the 12v senseline and the appliance it will be hooked to.