1 Need Some Help

Discussion in 'General Electronics Chat' started by electro-man, Apr 9, 2006.

  1. electro-man

    Thread Starter New Member

    Apr 9, 2006
    4
    0
    Hi guys, need some help choosing a resistor. I have a 12v 7.5aAh SLA battery and would like to alter the voltage to around 4 volts or so I'd like to use a resistor - what amp rating (ie: 1/4 watt, 1 watt etc.) and resistance.

    Cheers.
     
  2. n9xv

    Senior Member

    Jan 18, 2005
    329
    1
    It depends on load current. The series droping resistor is connected in series between the battery and the load. The calculation is;

    (Battery voltage - 4) / load current


    4 is the desired voltage in your case.


    With a resistive voltage divider like this, the voltage may not be stable depending on load current demands. Depends on what your trying to do with the 4-volts.
     
  3. paultwang

    Well-Known Member

    Mar 8, 2006
    80
    0
    What is the voltage tolerance of your load before you begin to damage it?
     
  4. Gadget

    Distinguished Member

    Jan 10, 2006
    613
    0
    You'ld be much better off with a voltage regulator, but again, need to know what sorta current your after...??
     
Loading...