# convert 12vdc to 1.22vdc

Discussion in 'The Projects Forum' started by electro01, Feb 27, 2013.

1. ### electro01 Thread Starter New Member

Jan 14, 2013
9
0
Hey guys...what would be the most efficient way
to drop 12vdc to 1.22vdc @80amps output? Could I just use a series of sand resistors or
something else? Sorry, I am kind of new at this.

Last edited by a moderator: Feb 28, 2013
2. ### crutschow Expert

Mar 14, 2008
13,021
3,235
You do realize that the resistors would be dissipating nearly 900 watts?

For efficiency you would need some type of switching regulator. But those aren't trivial to do at 80 amps.

What is this for?

May 11, 2009
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4. ### ohaib Asghar New Member

Feb 28, 2013
2
0
What is source that gives 12 v dc and 80 amp current?

5. ### DickCappels Moderator

Aug 21, 2008
2,656
632
The bank of resistors would be very simple and might work to your satisfaction if the load current is constant.

How accurate must the 1.2 volts be, and how stable is the load current?

6. ### Papabravo Expert

Feb 24, 2006
10,145
1,791
The implication of asking for 1.22 Volts is that the tolerance is plus or minus 5 milli-volts, which is pretty tight. On a switching regulator, 80 Amps out @ 1.22 v is about 97.6 Watts. assuming 80% efficiency you need 122 Watts in. for a 12V supply that is just over 10 Amps. This might be doable, but not for the faint of heart. Your big problem will be to find a suitable inductor to handle the current without saturating.

Trying to do this with resistors would only be possible with an absolutely CONSTANT load and the waste of tremendous amounts of power in the dropping resistor. If the load is 15.25 milliohms and the dropping resistor is 134.75 millohms then you get 1.22 Volts @ 80 Amps. and 862.4 Watts in the dropping resistor. Sounds pretty foolish to me, but what do I know.

7. ### bountyhunter Well-Known Member

Sep 7, 2009
2,498
507
You could do a sync rec buck converter.

8. ### t06afre AAC Fanatic!

May 11, 2009
5,939
1,222
The OP has some threads about earth batteries and joule thieves, used for to make energy. And I think this is somehow related to this.