diy solar

diy solar

Wire gauge from battery to inverter

ohmboy

New Member
Joined
Feb 1, 2024
Messages
88
Location
Out West
Hello,
Before I purchase wires and cables for my project, I would like to confirm that my calculations are correct.
My plan is to build a 24V 100ah LifePO4 battery bank. It will be used to charge my power tool batteries, lawn mower, drills, etc.
Below is the Voltage Drop Index (VDI) formula that I am using. Got it from JF Legaspi on you tube and using 2 for the %voltage drop.

VDI = Current x Distance (ft.) / % Voltage drop x Voltage

My Solar Panel specs: (I have 2 connected in series. Newpowa NPA100m-12I)
Pmax 100W
Vmp 19.06V
Imp 5.26A
Voc 21.82V
Isc 5.55A

LiFePO4 batteries to be purchased: 8x EVE LF105 3.2V 105Ah

Solar Panel (2 x 100W in series) to SCC wire:
VDI = 5.26A * 15ft. / 2 * (19.06v *2) = 1.035 --> 14 AWG

SCC to 24V battery wire:
I = 200W / 25.6V = 7.8125
VDI = 7.8125 * 2ft. / 2 * 25.6V = 0.30516 --> 16 AWG

Battery to Inverter wire: Looking at getting a 2000W inverter
I = 2000 / 25.6V = 78.125
VDI = 78.125 * 2ft. / 2 * 25.6V = 3.051758 --> 10 AWG

Will the above wires be sufficient for my project?
Also, do I purchase stranded or solid copper wires?

thanks advance.
 

Attachments

  • powerBank_sch.png
    powerBank_sch.png
    15.4 KB · Views: 8
  • vdiChart.png
    vdiChart.png
    3.8 KB · Views: 7
10 AWG from a 24 volt battery to a 2009 watt inverter.is risking fire.

You’re running 100+ amps through wire rated for 30 Amps.
 
I use this chart for ampacity:


IMG_1348.jpeg
To figure out amps for the inverter, the math I use is

(Inverter rated wattage) / (low voltage cutoff) / (inverter efficiency as a percentage)

To figure wire size:

(Inverter rated wattage) / (low voltage cutoff) / (inverter efficiency as a percentage) x 1.25 safety factor.

Some when sizing wire for wire inverter would use 24 volts and not a low voltage cutoff of 20 volts, and also not include a safety factor.
 
Last edited:
To figure out amps for the inverter, the math I use is

(Inverter rated voltage) / (low voltage cutoff) / (inverter percentage)

To figure wire size:

(Inverter rated voltage) / (low voltage cutoff) / (inverter percentage) x 1.25 safety factor.

Some when sizing wire for wire inverter would use 24 volts and not a low voltage cutoff of 20 volts, and also not include a safety factor.
Thanks again.
 
Back
Top