Good tiny tiny 12V ~20A PSU

[Intrepid]

I'm looking for a PSU for a "unique" project that needs 12V about 20Amps, I don't need the other rails, but dedicated 12V PSUs from DigiKey are about $200 and up, yet I've found some workable 240W (12V1 @ 18A) small form factor PSUs on newegg for under $50.

I recall some forum regulations about posting links to products so I won't do that here just in case.

I'm also looking for something small, its going into a tight (but very well ventilated) space, so mATX, SFX etc.

 

[antipesto93]

i remember there are some very old dell psu's that are tiny, i guess you could try searching 'small dell psu ' or something

 

[ratbuddy]

You want one that runs on 120v? What parts is it going to be powering? How much room do you have?

 

[CharlieCS]

Have you considered Pico PSU's ?

http://www.mini-box.com/DC-DC they are expensive however .

 

[Ben333]

For the three replies to the OP, I'm thinking that an older dell SFF power supply wouldn't have that amperage - even an older full size one might not, he said its for project and needs it to provide around 20 A, a pico PSU wouldnt make sense, that breaks the voltage down to 5V and 3.3V also and he only needs a 12V supply. Pico supplies don't offer near 20A either as far as I know.

How clean does the power have to be? Whats your budget? If the quality of the power isn't too critical, might I recommend an older outdoor DC lighting transformer? (Powers lights along walk ways) I've seen those up to 700W 12 - 14 V DC and for less money than 12 V "lab" power supplies. Other than that, unless you find a deal on a lab PSU, I'd say take a PC supply from a decent brand, add a load (resistor) to the 5V rail if required and use that. If the case is well vented, then you could strip the computer power supply of its case to save a bit of room.

 

[CharlieCS]

If you actually looked into it there are several Pico's that provide more then 20 amps, it does break up to 3.3 and 5 as well but i think size is the major concern here and pico eliminate that concern better then anything else .

 

[BossBorot]

IIRC the pico uses dc-dc conversion on from the 12v to 5v and 3.3v so if you don't use 5v or 3.3v you should be able to draw enough power from the 12v on certain models

 

[4GHZ_or_bust]

You may need to look into industrial use PSU. I've seen some when I used to work at an engineering company that designed and built custom balancing machines. There are PSU of various sizes and rating. The 12v I've seen once were capable of 25A and measured about 7inches by 4 inches and about 1.5" thick or about the size of decent 1000 watt ATX power supply squashed to about 1/4 the original height.

It's been so long I can't remember who made it but they were often listed as industrial PSU in catalogs.

 

[Intrepid]

Well, I don't want to spend too much on a supply that I'm ultimately going to be modifying anyway, I will be running them off of DC 76.8V by soldering into the bridge rectifier after the normal 120VAC input power stage. DC-DC converters and dedicated AC-DC supplies are expensive. The 12V power itself can be noisy and inaccurate, and having the 5 and 3.3 V rails is a bonus as I have another piece of hardware that can use those (no more than a few hundred mA). Someone I saw online had made this modification to the old Thermaltake purepower express PSUs made to add an extra 12V rail for video cards. I found one for $20 that can give me 19A, it should be enough to do the job, assuming it is suitable for the kind of modification I'm thinking of for it.

Has anyone here ever modified a PC PSU to run on HVDC (60-80V range)?

The application is cheep 12V power for an all electric motorcycle.

 

[nd4spdbh2]

i dont think you could easily take a pc psu that accepts ac and convert it to use higher voltage DC stuff.

 

[Intrepid]

In a PC PSU (or any switching unit that converts ac to dc), the first stage is a bridge rectifier that converts the AC into crude DC at between the peak and rms voltage of the AC applied, so for 120VACrms it will have 120-170 VDC after the rectifier. If you apply 120vdc to the output of the rectifier it will fool the unit into thinking it is connected to an AC supply, depending on how smart it is, but for $20 I doubt its smart enough to tell the difference. Many AC-DC converters can be made to work on DC by bypassing this initial rectification step.

 

[Evilsizer]

i think i got you covered, let me find the url...

*edit*
nvm seems you know the psu i was going to link to. in any case for others, im suprised this is still for sale at newegg. in case you need more POWER, check out this Thermaltake 650w job.... something i just saw for the MITX crowd, [http://www.thermaltakeusa.com/Product.aspx?C=1156&ID=1710#Tab0]Thermaltake A2422RU.[/url]

sorry if i went a bit off topic, didnt mean to.



wait, what? let me get this straight this psu project is for a electric bike?

 

[Intrepid]

I ended up choosing one of these to do the job.

http://www.newegg.com/Product/Product.aspx?Item=N82E16817338031

It should be enough, kind of sounds like a no-name brand from china, but thats all I need, the rest of my parts are from china except the controller.