A simple high quality 12Volt 100Amp Power Supply- Part3
If I was building one again I would do two things:
1) Check that the power supply worked before I soldered on the output wires by plugging it in and turning it on. The fan starts and the green LED blinks to show it’s in standby. Then with a voltmeter across any of the two adjacent blade connectors, push on a servo lead and twist the three bare ends together. The fan speeds up, 12V will appear and the LED will glow solid Green if it is OK.
2) Solder the wires on differently. I used heavy gauge silicone covered wires and soldered them to the end of the blades which is fine but it is hard to get a solid join and there is always the risk one will get knocked and come adrift. The better solution would be to use 25A wire which can be pushed in between the two blades of each connector, then soldered. It’s easy because the blades are gold plated and they grip the wire while you solder. Makes a stronger, neater job. See the pictures (which are of different similar supply – hence the five blades not four). I carved away the top ledge of the plastic connector frame with a Dremel to let the wires go down far enough.
How well does it work?
The supply is rated on the case at 106A @ 12V on a 200-240Volt supply and 74A on a 100-127V one. In addition it supplies 1A@ -12V and 7A@ 3.3V. The lower rating for US voltages is presumably a function of the maximum current allowed in the input stages.
The attached .pdf file shows the regulation as I increased the load to 118 Amps. That’s when I ran out of 12V loads! The total voltage drop from no-load to 118A is just 0.5Volt which is pretty impressive. It will also not start if the load is too high. For example two 12Volt cup heater elements, 10x 50Watt and 4x 160Watt light globes in parallel have too low a cold resistance and the supply simply refuses to start. I had to connect them separately one after another to do the full load testing.
I used a Camlight 400 in parallel with the resistive loads to supply the variable load and an Emeter2 to drive the Camlight and log the results. Both are brilliant gadgets! Thanks John, Mark, and Dave.
Pros and Cons
Pros: This is a compact, extremely high quality (the MOSFETS inside are the biggest I’ve ever seen), high current supply with excellent regulation. It requires NO modification to the supply or disassembly. I’m pretty sure you could run two in parallel if you wanted 200A as they are designed to do this in the server. I haven’t tried this but Everydayflyer got two of the IBM’s to work just fine. They automatically shared the load.
Cons: They aren’t as cheap as a PC supply or the older IBM ones (but they do deliver a lot more current). The fans make a noise, although it is not an irritating high pitched one. You can’t run two of these in series if you want 24V. Because the case is connected to ground through the power plug connecting the -12V of one to the +12v of a second will just produce a dead short. UPDATE: There is now another thread I started on Running two 12V supplies in series which covers this. It starts here: