12V DC Transformer

[RayCo]

For years, I have casually looked for a decent 12V DC transformer that I could put in my garage so that I could run 12V DC power to various locations throughout the garage along with the standard AC power that exists. There have been many times that I wanted a 12V source and wound up just going to the nearest car or tractor battery.

In looking for a solution, I've found 12V transformers that only put out 1 or 2 amps. This is no good. I'd like a MINIMUM of 30.

I was able to find higher amperage transformers when going the route that a high school physics teacher might go for classroom equipment purposes, but as I recall, everything was very expensive.

I've considered using a medium-duty battery charger, but I don't get a good feeling about leaving such a thing on 24 hours a day.

I've considered using a car battery and charging it when need-be, but this is pretty junky solution.

Anyone have any thoughts or suggestions?

 

[jinman]

Ray, what do you want to power with 12V DC? I would think the battery charger would be an excellent choice and easily portable to any location.

BTW: There is no such thing as a 12V DC Transformer. All transformers are AC. What you want is a 12V DC Power Supply. The small plug-in 12 volt power supplies are sometimes called transformers, but they have a transformer and at least a bridge rectifier in that case. Some have regulators too. A bench-type variable DC power supply could be used for any DC voltage level you need. I'd consider one of those if you have serious needs at different voltage levels.

 

[GaryBDavis]

If you use is for short periods of time, consider a 12V marine battery (deep cycle) and a trickle charger/maintainer. You can get a Schumaker battery maintainer available at Wal Mart for under $30. A battery maintainer like this one only puts out a couple of amps and will shut off when the battery gets fully charged. Since it continuously monitors the battery, it will start charging again when the battery drains back down. Compared to standard trickle chargers, they are designed made to be continuously hooked up to batteries for very long periods of time.

A typical marine deep cycle battery is around 100 Amp/hours, so you could run a 30 Amp load for about three hours.

You can buy both these items for close to $100 and the battery, if properly maintained, should last 4 plus years.

 

[ultrarunner]

I use an old Lionel train transformer... it has different voltage taps on the back and the thing weighs about 12 pounds.

 

[Wayne County Hose]

I have researched and priced 12 dc power supplies. No thanks. I did what Gary said, a 12v marine battery. I could replace it every 3 years for the next 20 years and still be ahead on money.

 

[gemini5362]

I am glad that you found a way to do what you need. You probably could have taken a variable ac transformer and then took the diode pack out of an alternator and made what you need. You can pick up variacs (variable ac transformers at swap meets and flea markets sometimes for a few bucks. You did not tell us what you you were going ot use it for. Different things need different amounts of regulation and filtering capacity. Using the 12 volt battery gives you almost pure dc. If you use it without the battery charger attached you will have no ac ripple. Using the trickle charger wont make enough difference for you to be able to detect without some very good test equipment so it really wont make a difference. The better battery chargers with the wheels on them and start capabilities will give you the power you require with some filtering caps on the output they can give pretty clean dc power. If the battery does not work out message me and I can tell you what you need to do

I am not real worried about it but I should point out that if you are keeping a battery under constant charging there is a possibility of it giving off gas and being an explosive hazard

 

[gordon21]

If you decide to set up outlets in the shop, look at boating supply catalogs for all types of 12v outlets. You can have them mounted flush on walls, locking caps, etc. There are lots of choices out there in plastic, stainless, etc. BOAT-US or West Marine are good places to start looking. They have outlets, circuit breaker boxes, wiring, busbars, fuses, mini panels, faceplates, etc.

A marine battery with proper wiring would be fine for a permanent installation with attached slow/intelligent charger. A typical 21' boat can easily have a couple hundred feet of wiring in it. Use common sense and have everything labeled, bundled and clamped so it looks neat and professional.

 

[cmuncy]

If you go the battery route, make sure you have a fuse at the battery to prevent the leads from causing a fire in teh event of a short.

Also, you might want to purchase either a maintenance free battery or a gell battery ( Optima) so that you wont have to worry about electrolyte levels.

 

[RayCo]

Thanks a lot for the replies. I will look into the marine solutions. I do indeed want to have 12V receptacles of some kind (even just spring-posts and cigarette lighters would be fine) throughout my garage for any number of things that come up.

Not that this is the only thing, but I have old car stereos lying around that would be better than the 1980's boom box I have setup. Also, most electronics like cell phones and things these days have 12V chargers made for cars. This would allow me to charge things in my proximity without disrupting my normal charging location in the house.

 

[Keoke]

Ray Co, if you looking for a cheap 110 ac to 12 dc power supply consider one from a wrecked RV. Many of these will give the 20 amps dc you are looking for.
However, if want to keep the AC ripple down you will have to put a 12v battery in parallel with the load to flat line the voltage. For low amp requirements with minimum ripple a 12v power supply would be your best shot.

cheers,

 

[Lazy]

Hi
You might consider a power supply from an old computer
Charlie.

 

[mbrule]

Hi,

Why do you need 30 Amps? So far you have mentioned car stereos, and cell phone chargers. You will run most car stereos on less then 5 amps, unless you have high power amps, subwoofers etc. Cell phone chargers will draw less than an amp. Do you have other uses?

You might look at commercial power supply companies, I use a lot of supplies from Astrodyne (www.astrodyne.com) for around a $100 you can get a 20 amp switching power supply. If, as I suspect, you don't really nead 30 amps, you can get one significantly cheaper.

Hope this helps.

Matt

 

[Soundguy]

If it were me, I'd get a small motorcycle battery plus a charger capable of doing 10a. have the charger on a switch so that you could turn it off when not in use. ( i see many chargers that have a 2a/10a rate.. so you can select the high rate when you need it ).

Wire up a fuse block with taps for each circuit and keep the batter in the line but out of ircuit with a isolator switch. Kick the batt charger on when you need power.

that will be the cheapest route.

as others have said.. xformes are usually ac.. except for autotransformers for high votlage whivch are colapsing field ( pulsed) dc.. etc.. not what yuo are looking for.

hey jinman.. when did you change your avatar?

soundguy

 

[gemini5362]

If it were me, I'd get a small motorcycle battery plus a charger capable of doing 10a. have the charger on a switch so that you could turn it off when not in use. ( i see many chargers that have a 2a/10a rate.. so you can select the high rate when you need it ).

Wire up a fuse block with taps for each circuit and keep the batter in the line but out of ircuit with a isolator switch. Kick the batt charger on when you need power.

that will be the cheapest route.

as others have said.. xformes are usually ac.. except for autotransformers for high votlage whivch are colapsing field ( pulsed) dc.. etc.. not what yuo are looking for.

hey jinman.. when did you change your avatar?

soundguy

soundguy, USUALLY AC ? LOL I have not seen a lot of pulsed dc systems most of the ones I have seen use the DC to drive some type of oscillator and then convert the hire voltage back to dc. I would think that for all intents and purposes on a tractor net that saying all transformers are AC would probably not get too many people that would argue

 

[Soundguy]

soundguy, USUALLY AC ? LOL I have not seen a lot of pulsed dc systems

Really.. you havn't seen many... You walk or ride a bike alot? what about an auto transformer?

You know, for a basic example..... and ignition coil and a set of breaker contacts with a condensor across them.? ring any bells?

I would think that for all intents and purposes on a tractor net that saying all transformers are AC would probably not get too many people that would argue

Some other forums.. but not here. lots of sharp people here.. and if you make a blanket statement like that and leave a big loophole in it.. someone will call you on the rug pretty quick.. Like I said.. had i said all xformers are run off AC.. it would'nt have taken very long for someone to post about autotransformers. After you have experienced enough 'power rebuttals' for omitting a seemingly insignificant yet valid fact.. you learn to CYA when writing posts of a technical nature.. etc..

soundguy

 

[slappie]

I have done the exact thing you mention in my garage.

I flush mounted a car stereo into the wall and speakers into the ceiling along with an amp and subwoofer.

I used a 20Amp power supply that I got from Fry's Electronics store.

Samlex may offer 30 amp but they are not available at Fry's.

The 20Amp is plenty to keep my garage rocking very well.

The brand is Samlex and it was about $120.

Here is a link
http://shop3.outpost.com/{6xhFYh526cskijrVX9myug**.node3}/product/1927131;jsessionid=6xhFYh526cskijrVX9myug**.node3?site=sr:SEARCH:MAIN_RSLT_PG

 

[Soundguy]

Dang that alotta money.

Could build a good one from surplus computer supplies..

soundguy

 

[schmism]

is there a reason a car battery charger wont work?

they are common in RV's you could check out the RV supply places

radio shack and the like usually feature a few powersupplies....

ham radio operators use them alot to make a portable radio more permant.... check the ham supply places (although there/our power supplies are usually high end to avoid interferance etc)

 

[RayCo]

Hi
You might consider a power supply from an old computer
Charlie.

That's rather brilliant! Especially since I have about 10 old power supplies sitting around!

 

[RayCo]

Why do you need 30 Amps? So far you have mentioned car stereos, and cell phone chargers. You will run most car stereos on less then 5 amps, unless you have high power amps, subwoofers etc. Cell phone chargers will draw less than an amp. Do you have other uses?

I'd mostly like to have 30 amps just for room to grow. I think what originally caused me to want 30 amps was the power seat in my project car stopped working, and I needed to move it. So, I ran some jumper wires from the battery to the harness for the seat motor, which worked. But it'll be nice to have 30 amps available everywhere. Especially if I make a lounge in my garage with power seats from a Cadillac or something.