How to convert 120V, 20Amp wall power into 12V, 700Amps?

Question

If you were MacGuyver what would be the simplest method using everyday items (if even possible)? I read one guy's article about a homemade battery charger he made using wall power, a lightbulb as a resistor, and some other house junk. It was pretty innovative.

Answer 1

The total power out put cannot exceed the source. The total Watts in a 120V/20A circuit is 2400 W. (Volt X Amp=Watt)
You cannot get 12V/700A because this would necessarily be 8400 Watts. The best, 100% efficient, conversion from 120V/20A would yield 12V/200A.
I doubt even MacGuyver could do this without a step-down transformer or at least the insulated wiring necessary to wind a 10:1 ratio windings around some sort of core or small frame.
Then again, MacGuyver has done some pretty amazing things.

Answer 2

You can get the needed power from a 40 amp 240 volt electric stove outlet. A 10 KVA welder will have a large enough transformer, but the voltage will be too high and the current will be too low. You would need to remove the secondary winding and replace it with fewer turns of larger wire. Wire large enough to carry 700 amps will be difficult to wind on the transformer, so several parallel windings might be needed. Although 700 amp rectifiers may be available, several sets of rectifiers would probably be easier to find and heat-sink. These are not everyday household items, but conceivably available as industrial salvage.

Answer 3

LeAnne's got it right

And keep in mind that the secondary winding of that transformer has to be able to handle the full 200 amps.

DIodes to rectify the AC into DC with that current capability are available.

Answer 4

A transformer array (with resistance circut should do the trick, but thats a lot of amps be careful