30 Volt Computer Power Supply Stack
Or: What do you do with a bunch of old computer power supplies?
This site was last updated on July 22, 2004
Wow! What a pile of power! Let's see what we can do with these gems!
These surplus Dell power supplies were chosen for a very good reason - I got them for free, and I got a LOT of them. A bonus was that I discovered that these did not need a standby load connected to the supply to keep them running - just apply mains power and close the Start lead to ground.
Oh Wow! Whatta' mess!! Can we ever figure this out? You bet'cha!
The nameplate says we can get 29 amps @ 5 volts - with no load on the other lines, these babies tested out at 40 amps!
Here's the assembled Tower of Power. Six supplies in series make 30 volts at 35 amps - that's a total of 1050 watts! Taps are available every 5 volts from 5 to 30 volts.
This side view shows that there is a piece of cardboard separating the cases of each power supple so they do not short circuit each other. The supplies are strapped together with clear packing tape. The side vent holes are covered, but the holes on the ends are left open to allow cooling air to flow through the supplies.
The business end of the power supplies. Note that all of the red and all of the black wires have been connected together to form a (+) and (-) cable from each supply. you can see that the black (-) lead of the bottom supply is free. It is the negative end of the Tower of Power. It is also connected to the case of the bottom supply. The case of the bottom supply is also connected to earth ground through the power cord. note that none of the other supplies have their cases grounded as they are all above ground potential.
This shows the plastic insulators I made to hold the tap point terminals between each power supply and it's neighbor.
A close up of one of the tap points. Note also that all the other wires from the supply have been cut off as they exit the case of the supply. The gray wire is the power supply start line. It is connected to one of the black ground leads from that supply. That starts the supply running as soon as the mains power is applied to the supply.
The mains connector going to the top supply. Note that it has only the mains wires connected to it. The ground lead is not connected.
An overall view of the Tower of Power mains wiring. The power cord goes to the bottom supply which has its case grounded to earth through the power cord. A separate set of power wires splits off of the first mains connector and feeds two supplies. That reduces the mains voltage drop between the supplies under load and ensures that all the supplies get the same mains voltage.
A closer view of the mains power distribution system.