# Best/Inexpensive DC Power Supply



## TomS (Mar 10, 2014)

I have a surplus RV slideout gear motor, don't ask why I have an extra motor, I am adapting to my mill/drill to raise and lower the head.  It is rated 12 VDC 30A at maximum load.  The power supplies I've found at a reasonable price don't come anywhere near 30A.  Any suggestions?

Tom S


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## xalky (Mar 10, 2014)

TomS said:


> I have a surplus RV slideout gear motor, don't ask why I have an extra motor, I am adapting to my mill/drill to raise and lower the head.  It is rated 12 VDC 30A at maximum load.  The power supplies I've found at a reasonable price don't come anywhere near 30A.  Any suggestions?
> 
> Tom S


A car battery charger. maybe.


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## Terrywerm (Mar 10, 2014)

Considering that the head on your mill/drill will probably not fully load your linear actuator, it will probably not use a full 30 amps, but I think you can expect it to use 15 to 20 which still puts it outside the realm of most power supplies. As already mentioned, your best bet might be a battery charger.


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## DMS (Mar 11, 2014)

If you have a surplus electronic store nearby, that would likely be the cheapest option. You can also try E-bay, I have see some larger capacity switching supplies on their for not too much. Another option is PC power supply. Some can pump out a lot of current. I have one here that has 2 channels rated at around 14A each. They tend to be cheap too.


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## AlanR (Mar 11, 2014)

Amazon has some 30A/12V supplies for around $30 that's what I looked for but there probably are others.


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## JimDawson (Mar 11, 2014)

How about a car battery!  Throw it on the charger occasionally, you probably need a new battery in your car anyway. Keep the old one for your mill.


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## furpo (Mar 11, 2014)

http://www.ebay.com/sch/i.html?_odk....m570.l1313&_nkw=30a+DC+power+supply&_sacat=0


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## TomS (Mar 11, 2014)

Thanks to everyone for their input.  I like the idea of using a computer power supply but will have to order one.  In the mean time I'll search through my stash of battery chargers and see if I have one with enough amps to power up the motor.

Tom S


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## furpo (Mar 11, 2014)

I think a normal computer power supply will be way short on amps.


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## Hawkeye (Mar 11, 2014)

A trickle charger will do the job if you use it to keep the old car battery that Jim suggested topped up. When you use the battery to run the motor, the charger will put it back at a slower rate. Lead-acid batteries need to be kept fully charged, so leaving a very small charger (say, 1 amp) on it all the time won't hurt it. A big charger would hurt it, if on all the time.


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## SEK_22Hornet (Mar 11, 2014)

If you go the battery and charger route, make sure the charger you use is actually a battery maintainer - one intended to put on vehicles in storage. They are set up to maintain a full charge battery without overcharging and boiling out electrolyte. Also keep in mind that a charging battery emits flammable gasses - this may present a fire hazard - especially if you weld or cut, or even grind metal nearby. I'd suggest the switching power supply - about $30 and you will be set and not have to worry about the battery. Something like this one would be plenty, especially since the load will be intermittent. An old battery charger with the start or boost mode might work as well -


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## Millbo (Mar 13, 2014)

Idea #1
Car battery w/ trickle charger.

Idea #2
Electric motor to run cars alternator, will require the battery to excite the field.
A Permininate Magnet Generator (PMG) would be best in this case but not sure if they come in low enough voltages or current ratings.

Idea #3
If you have a Variac in your shop then just build yourself a variable DC power supply. You just need a full bridge rectifier. 
The 50 amp / 1000 volt model is $5 on this site. Be sure to mout the rectifier to a heat sink.
You can put a capacitor across the output to smooth the ripple but I don't forsee you needing that for this application.

http://www.myshopkart.net/blacksonline/product_info.php?products_id=49792919&



Just a couple thoughts.

I've built #3 to test some DC motors with.


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## TomS (Mar 13, 2014)

Thanks to everyone for the list of ideas.  I did find a 10 amp battery charger stashed away in my junk.  Hooked it up and it did move the head up and down although the gear motor struggled a bit more raising the head.  Could be the motor would run better if it was fed more amps.

I also have a PC power supply I'm planning on using.  I've got another thread going on this as I'm not at all electrically or electronically inclined.  The power supply is rated at 20 amps.  Hopefully it will work better than the battery charger.

Tom S


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