# High Current Low Voltage Power Source

#### Clickster

I am in need of a high current low voltage DC power supply, around 8 volts and around 250 Amps would be ideal.

A transformer could take a 110v 20a house line and using Pincoming = IPVP = Poutgoing = ISVS and
get (110vx20a)/8v= and get 275a which is good.

But how do I make that DC?

I know that diode bridges are the norm for converting AC current to DC current but I have done a fair amount of browsing and found none that have the requirements that I need. I think the most I have seen are like 35 amp continuous and 400 amp surge.

Anyone have any ideas?

Related Electrical Engineering News on Phys.org

#### Gnosis

I am in need of a high current low voltage DC power supply, around 8 volts and around 250 Amps would be ideal.

A transformer could take a 110v 20a house line and using Pincoming = IPVP = Poutgoing = ISVS and
get (110vx20a)/8v= and get 275a which is good.

But how do I make that DC?

I know that diode bridges are the norm for converting AC current to DC current but I have done a fair amount of browsing and found none that have the requirements that I need. I think the most I have seen are like 35 amp continuous and 400 amp surge.

Anyone have any ideas?
It would be helpful if you stated what you’re attempting to power, as well as the duration of time it must be continuously powered. Must you use 8 volts?

#### Clickster

Its for an electrolysis experiment and duration of time depends on amperage. I think a max of 10 volts needs to be established, if it is over 10 volts, other materials with a higher reduction potential could come out.

Anything under 50 amps will not be cost effective.

Last edited by a moderator:

#### jeff morriss

At these low voltages and high currents the best way to go is a switcher. Don't even try to build your own. Go on Ebay and look. I have seen supplies like this at reasonable costs.

#### Topher925

Do you have a price in mind? There's a lot of industrial power supplies out there that can do this no problem. However, they cost a small fortune and are very big and heavy.

#### bipolar

Do you have a price in mind? There's a lot of industrial power supplies out there that can do this no problem. However, they cost a small fortune and are very big and heavy.
They also have efficiency levels high enough to pay for themselves after a long period of use in electroplating. The small ones (under 100A) aren't super expensive - roughly $3-$4/Amp, but are very efficient switching supplies with extremely stable output.

#### Clickster

I found this on eBay, it looks to be what I need and not too expensive either. The only thing that it needs is 220v...

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&ssPageName=STRK:MEWAX:IT&item=400008509005 [Broken]

Last edited by a moderator:

#### kk_joshi99

Its for an electrolysis experiment and duration of time depends on amperage. I think a max of 10 volts needs to be established, if it is over 10 volts, other materials with a higher reduction potential could come out.

Anything under 50 amps will not be cost effective.
the voltage required for electrolysis is 1.24V only so wat i suggest u is that u connect 12V supply to 6 cells in series in this way u can avoid heat produced and generate more h2...the current drawn is dependent on the resistance of the cell u just need to take care of the voltage and heat generated...

Last edited by a moderator:

#### fbs7

That reminds me when I was 12 years old, with that cool new chemistry box, thinking "bah, who needs a battery, I'll get a faster electrolysis with a higher voltage!" and just dropping two wires into a cup of saline solution and then connecting them to a 110V power plug...

... ah, good times!

Last edited:

#### Antiphon

Use a 1200 Watt ATX power supply. You'll get 12 volts, not 8 but even the really good ones can be had for under \$300. You may have to plug it into a dummy motherboard to make it turn on but that's easy too. Tap your power off the lines that would go to the graphics cards.

250 amps is asking too much. Even at 8 volts that's 2000 watts, too much for one standard US outlet to supply.

#### Averagesupernova

Gold Member
The only thing that it needs is 220v...
So what's wrong with 220 volts? If you are not comfortable and capable enough to be working with 220 volt mains electricity then I don't think you should be messing with this project.

#### NascentOxygen

Mentor
So what's wrong with 220 volts?
As the original poster has not logged in since he asked about a high current supply, and that was 3 years ago, he may no longer be closely following this thread.

Just wondering, what voltage are home electric welders?

#### Averagesupernova

Gold Member
Oh jeez I hardly ever do that. I always look at the dates. Oh well...

#### jim hardy

Gold Member
2018 Award
Dearly Missed
Just wondering, what voltage are home electric welders?
there are small ones that'll run from a 115volt 15 amp outlet and deliver sixty amps or so.

the old standby cathedral shaped Lincoln 225 amp needs 230 volts.
i run mine from a dryer oultlet.

new microwave ovens have inverters - i'm curious if one could rewind the output transformer with a few turns of large wire.......

#### NascentOxygen

Mentor
there are small ones that'll run from a 115volt 15 amp outlet and deliver sixty amps or so.
But what is their open-circuit voltage? They are just a robust transformer, right? Or do electric welders include rectifiers?

I'm thinking a welder might furnish the avid experimenter with a robust source of low voltage AC?

#### jim hardy

Gold Member
2018 Award
Dearly Missed
But what is their open-circuit voltage? They are just a robust transformer, right? Or do electric welders include rectifiers?

I'm thinking a welder might furnish the avid experimenter with a robust source of low voltage AC?
Welders make perhaps seventy volts to strike the arc.
Better ones have rectifiers and will say " DC "

Hobbyists are using microwave oven transformers (aka MOT) to make low AC high current for spot welders. They remove the high voltage winding and replace it with a few turns of BIG wire.

Four re-wound MOT's and something like these might make a versatile setup...
http://www.ebay.com/itm/Bridge-Rectifier-50-Amp-10-1000-volt-KBPC50A10-Aluminum-Casing-HEAVY-DUTY-/130592483935?pt=LH_DefaultDomain_0&hash=item1e67eb2a5f
and there's usually 150 amp ones on Ebay.

<<<WARNING>>> :: a microwave oven transformer with its high voltage winding still there is more dangerous than a handgun.
NEVER enegize one until the high voltage winding is physically removed. And i mean removed with a hacksaw.

### Physics Forums Values

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving