Hi All,
I have come across a few online voltage drop calculators and I believe I am misunderstanding the application or input parameters for these calculators because the voltage drop results I calculate by hand conflict with the calculator results. I have posted an example below.
Assumptions
Wire: 14 awg, CU Wire, I used 3.14 Ohms/Kf or 0.00314 Ohms/ft for a resistivity
Parameters
Voltage: 12 VDC (12 Vdc battery)
Rwire: 0.157 ohms (I am using 50' of wire, 0.157 was found by .00314*50')
Rload: 4 ohms
Schematic:
Now, according to typical voltage drop methods using the online calculators. Vdrop is found by using the load current multiplied by the wire resistance. I agree with this, however I am confused why they do not factor in the wire resistance in series with the load when determining load current. See example below.
Typical Online Voltage Drop Calculator Method
Load Current (IL) = Voltage/Rload = 12/4 = 3 AMPS
Vdrop = IL* (2*Rwire) = 3 * (0.314) = 0.942 Vdc
My Calculations
Rtotal = Rload + 2*Rwire = 4.314
Load Current (IL) = Voltage/Rtotal = 12/4.314 = 2.78 AMPS
Vdrop = IL* (2*Rwire) = 2.78 * (0.314) = 0.873 Vdc
I am just looking for any feedback for this discrepancy.
Thank you all for your time,
Chad
I have come across a few online voltage drop calculators and I believe I am misunderstanding the application or input parameters for these calculators because the voltage drop results I calculate by hand conflict with the calculator results. I have posted an example below.
Assumptions
Wire: 14 awg, CU Wire, I used 3.14 Ohms/Kf or 0.00314 Ohms/ft for a resistivity
Parameters
Voltage: 12 VDC (12 Vdc battery)
Rwire: 0.157 ohms (I am using 50' of wire, 0.157 was found by .00314*50')
Rload: 4 ohms
Schematic:
Now, according to typical voltage drop methods using the online calculators. Vdrop is found by using the load current multiplied by the wire resistance. I agree with this, however I am confused why they do not factor in the wire resistance in series with the load when determining load current. See example below.
Typical Online Voltage Drop Calculator Method
Load Current (IL) = Voltage/Rload = 12/4 = 3 AMPS
Vdrop = IL* (2*Rwire) = 3 * (0.314) = 0.942 Vdc
My Calculations
Rtotal = Rload + 2*Rwire = 4.314
Load Current (IL) = Voltage/Rtotal = 12/4.314 = 2.78 AMPS
Vdrop = IL* (2*Rwire) = 2.78 * (0.314) = 0.873 Vdc
I am just looking for any feedback for this discrepancy.
Thank you all for your time,
Chad