Looking for a low cost 12v power supply

[stercorarius]

Long story short, I'm building a box to test trailer lighting without having to bring in a tractor just for the pigtail. It needs to run off 120vac. I need a 12v power supply that really only needs to be able to do about 180 Watts right? I've only been able to find ones in the triple digit range. Anyone else have ones that they have found for a low cost alternative?

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[one9gt]

YouTube CPU power supply 12v bench tester... plenty of tutorials out there


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[ryan20021982]

YouTube CPU power supply 12v bench tester... plenty of tutorials out there

Was going to say that also, they are cheap and you can also get different voltages from them for testing other things.

 

[stercorarius]

YouTube CPU power supply 12v bench tester... plenty of tutorials out there


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I'll have to see if my brother has any old 400w PSUs laying around from computer builds.

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[maxpower_hd]

At work we have a home made one that uses a two wheeled dolly and a truck battery instead of plugging in. It has a 7way and a long cord wired onto it for testing trailer lights.

I am still in the thinking stages of building one that runs of a battery in the back of my truck so I can test lights on multiple trailers at a time without loading up the home made tester.

 

[pedrodagr8]

YouTube CPU power supply 12v bench tester... plenty of tutorials out there


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Definitely this. For electronics, a CPU PSU converted to a power supply is a really really bad idea. For this usage case, a CPU PSU converted to a power supply is damn near PERFECT for what you want to do. One thing I will mention, this is something some YouTube tutorials don't mention or gloss over, if you do use a CPU PSU put a permanent load on the 5V line. Some CPUs do not handle high loads on the 12V rail but not the 5V (or 5V but not the 12V) and the voltage can drift really really far out of spec. So to make it easy, just permanently install a light bulb on the 12V line (treat it as an indicator lamp that the PSU is on) and call it a day.

 

[pstemari]

I don't know that a computer PSU is going to drive 15A on the +12V rail. IIRC it's the +5V that provides the most power.

If you can find a 15A dumb battery charger that should work well.

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[pedrodagr8]

I don't know that a computer PSU is going to drive 15A on the +12V rail. IIRC it's the +5V that provides the most power.

If you can find a 15A dumb battery charger that should work well.

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That hasn't been true in a long long time. The last time that computer power supplies used a large 5V rail was the P4 days. These days most computer PSU's put out around 50-80% of their power on the 12V rail. It isn't uncommon to see PSUs now with 50+A 12V rails. Some of the 1500W systems will have over 100A possible on the 12V rail. See the Corsair AX1500i as an example, which has a 12V rail rated at 125A. Now obviously OP is not going to use a $300 PSU for this job, just using it as an example to show how the industry has moved dramatically from the P4 days of large 5V rails.

 

[EOC_Jason]

I don't know that a computer PSU is going to drive 15A on the +12V rail. IIRC it's the +5V that provides the most power.

If you can find a 15A dumb battery charger that should work well.

Old computers (like circa Y2K) primarily used the +5V for power, however with modern computers because of the graphics cards and overall power demand the +12V rails have taken over as the primary power source.

I picked up a 20A continuous power supply at a garage sale for $8. Guy used it to power his old CB equipment back in the day.

Also just look on ebay for 12V open frame / closed frame power supplies. I bought a whole box of them for cheap when I only needed one. In fact, I'm going to go dig in my closet and see what they are rated at, maybe it will work for you...

 

[EOC_Jason]

Just found them, sorry they are only rated for 5A @ 12V.

But yeah, if there is a computer repair place near you, I bet they would give you a pile of old power supplies for free.

Or you can search ebay for "power-one power supply" and find you something nice for a reasonable price.

Or just get a SLA 12V battery from wallmart or a sporting goods store that is used to power deer feeders and such? Just put it on a charger when not in use.

 

[skruft]

For higher amperages I found a couple of RV power supplies at the flea market.

 

[gungatim]

computer psu will work just fine. I made one to run some cb's and other stuff on 12v. to get full power, connect all the yellows together for +12v, and all the blacks together for ground. a 200 watt supply will give you 8 amps, if you really need 15 amps, get a 400 watt supply. add a USB to the red wires to get 5v to charge stuff if you want...

 

[Roberts210]

Go to SurplusCenter.com find the Transformers and Bridge Rectifiers page. You can get a 120 VAC to 12 VAC, 3 amp transformer for $5. Then get a bridge rectifier from Radio Shack for about $1.50 and run the 12 VAC output from the transformer through the bridge rectifier to turn it into 12 VDC. Bingo.

 

[M_George]

This is where Radio Shack used to come in. You could get the plans and parts and build it custom.

 

[Richard Cranium]

I think I have read a thread on this a few years ago.

 

[engineer2]

Here ya go for $50, less whatever coupon you find.
http://www.harborfreight.com/3-in-1-portable-power-pack-with-jump-starter-62306.html

 

[stercorarius]

At work we have a home made one that uses a two wheeled dolly and a truck battery instead of plugging in. It has a 7way and a long cord wired onto it for testing trailer lights.

I am still in the thinking stages of building one that runs of a battery in the back of my truck so I can test lights on multiple trailers at a time without loading up the home made tester.

I'm primarily mobile so the plan is to make it in a Ridgid case. I'll wire a set of banana plugs into one of the tool boxes on my service truck for switched auxiliary power and do banana plugs on the box. Then I can run it off my pickup or a wall outlet. One idea I've been toying around with but haven't done any research for is to gut a tool and run it off a power tool battery.

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[gungatim]

when you are done post it up. I've been wanting to make one too but never got around to it. somewhere I had a pic of someone's setup they made in a small tackle box with a battery inside, had lights for each, a flasher, and 4 5 & 7 way connectors that fit inside...can't find it though.

 

[66HertzClone]

I followed instructions I found on the Instructables web site, I set it up using banana plugs and a meter for both volts and amps for the 12 volt supply. Sorry the damn picture is upside down. I think I kept the instructions as a pdf on my garage PC, I'll check when I get home. In order for this to work a resistor was required to be used, a dummy circuit is created using the resistor in order to fool the power supply into turning one.

 

[Brian_WK]

A SLA Battery and a tender. Make up a control board with switches to test your light functions. Use battery power when testing remotely or not near a plug. Plug it in and get the battery boosted back up. I used a little 200MaH SLA battery to test the trailer lights on my trailer after I rewired them worked fine.

Brian

 

[desertdog256]

Ham radio power supply fits your requirements of 12v DC from 120v AC with plenty of amperage.

MFJ makes one that does 22 amps continuous at 13.8v and it sells for around $85.

Try mtcradio.com or hamradio.com

 

[olds463]

https://www.circuitspecialists.com/csi-power-supplies

 

[Grandmaster]

I ran across this for RC chargers. http://www.2zo-rc.com

They are reasonably priced and multiples can be hooked up in parallel or series to deliver more amperage and volts.

 

[FigureItOut]

One idea I've been toying around with but haven't done any research for is to gut a tool and run it off a power tool battery.

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What power tool systems do to have? Probably no need to gut a tool.



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