Load test 12V on power supply???

[jonnyGURU]

I've got one of those load testers we used to use on car batteries when I was a car mechanic. It's not the digital one, but it's the big one with the guage and the load switch.

You know the device: You put it on a battery and put the load on it and if the needle drops below a certain point, the battery may be toast or at least need charging and if you hook it up to an alternator and the needle drops than the alternator has issues.

I Was wondering if I had jumpered the green and black on a power supply as to energize it and I hooked this puppy up to the 12V rail and flipped the switch... what's going to happen and if nothing really happens, does that prove anything to the worthiness of the power supply?

 

[Slaimus]

You might actually damage the power supply to run it bare because it has a minimum draw required on each rail.

 

[Mark R]

Hmm. a car battery load tester may be a bit OTT. However, I have stress tested PSUs before by plugging a pair of foggies into a spare pair of disk drive connectors.

 

[jonnyGURU]

Originally posted by: Slaimus
You might actually damage the power supply to run it bare because it has a minimum draw required on each rail.

Nah. On the bench I've used power supplies to do nothing but spin fans, etc. You don't HAVE TO have a load on all of the rails.

Besides, if I damage the power supply, I've made my point.

On that point, why not put the load tester on all of the rails. Nobody said it HAD to be on the 12V just because it's made for a car.

 

[jonnyGURU]

I found specs for my tester online. Apparently it drops a 100A load on 12V. That would be equivalent to 1200W's! SWEET! Let's see if overload protection works!!

 

[jonnyGURU]

Well... At least I know the overload circuitry works.

I used an Ultra 300W. Paper clipped the turn on lead, clamped the tester down onto some nails. Shoved the nails into a couple of the drive Molexes and plugged in the power supply.

The power supply fired up and the tester read 11.6V on the 12V rail. I then flipped the switch and the needle dropped. Cycled the power switch and it fired right up again and went right back up to 11.6V.

I thought that I'd at least see a voltage jump before the protection kicked in, but I didn't.

I guess it really was OTT. But it makes me want to get a load tester that allows me to dial in the load. They have some of those out there, but so far I've seen them all around the $300 price range.

 

[Zepper]

Use a batch of 50W/12V halogen bulbs wired in parallel and switched to add one at a time - that'll give you approx. 4 Amp steps. Could throw in some smaller bulbs to get finer steps at the limit. TEST TO FAILURE! That's my motto...
.bh.

 

[jonnyGURU]

Like car halogens? They're 12V. Hmm... I could do that.

 

[Operandi]

Originally posted by: jonnyGURU
Like car halogens? They're 12V. Hmm... I could do that.

Do it! I double dare you!

 

[jonnyGURU]

Hey! I'll do it.

Actually, I just saw that used in a test today. The guy had a wood board with a bunch of lights going across it.

That's freaking BRILLIANT! Actual PC component draw fluctuates too much. A drive might be 10W on startup, but only 2W idle and 5W while seeking. A 12V 40W light is going to pull 3A no matter what!

FREAKING AWESOME!!!

Ooh! Ooh!

If I wire up the low beam/high beam to a switch, I can increase my load by 50% with the flip of a switch!!!! Ooh! Ooh!

 

[Zepper]

And on a cold winter's day, the test rig can keep your lab toasty...
.bh.

:moon:

 

[jonnyGURU]

Originally posted by: Zepper
And on a cold winter's day, the test rig can keep your lab toasty...
.bh.

:moon:

Haha! That's true. I've got a pair of halogen work lights in the garage and I get closer and closer to the light as the night closes in NOT because it's getting darker outside.

I'll start building it this weekend and post pics.

 

[jonnyGURU]

Hehe... I wired up a 1157 30W high-beam bulb so both filaments lit up and hooked it up to my PC while it was running and I immediately got a BSOD.

SWEET!

I only have two bulbs for now, which should be good for only 5A. I guess I should pick up a whole bunch more, drill some holes in a board the size of the bulb socket ($100 per bulb, $4 per socket) and let her rip!

Autozone has a 12V terminal block too that I can screw down all of the lights to and then plug into the power supply. Then, I only have to touch these little buttons to turn on the lights. This is going to be sweet.

 

[jonnyGURU]

Ok. I've been busy lately and am only half way done with this project. I can really only test 300W power supplies now, but I plan on adding four more lights and I've got a Kill-A-Watt coming that I can plug into the AC side of things.

I ended up not using halogens due to cost. Halogen bulbs are about $10 each.

I said I'd take pictures of the Ghetto-fab Tester.

Observation.... It gets HOT AS HELL standing a foot above these bulbs!!!!