Wire sizes vs current capacity {split from Shops that install DC-DC charger}

[Gr8ful]

As I just states NO ONE uses a 10% loss chart unless you want a fire. Standard is 3% or 2%. If you don't understand electricity DON'T Guess then try to prove you're correct! It shows a major flaw in your character and/or lack of.
Your chart is 120VAC NOT 12VDC.

 

[rruff]

Yes, I know you said it, and you are still wrong. It won't start a fire, and the temperature has nothing to do with how long the wire is. 8 gauge running 40A will be the same temperature regardless of the length, and the temperature will be conservatively below the danger threshold.

Also, the required wire size for AC or DC at the same amperage is... the same.

Your comments regarding my lack of understanding of electricity and how I should be humble enough to learn, would best be directed to yourself. I was going to write out the equations, but then figured that would just confuse you more...

 

[Gr8ful]

What is the maximum voltage drop in a 12v circuit?

This loss shall not exceed: 12-volt system: 0.500 volts maximum voltage loss. For a 24-volt system: 1.000 volts maximum voltage loss.Jun 1, 2013
So this proves your 10% is wrong & would be 1.2 voltage drop which is 2.5 times the .500 max voltage loss shown. It's actually 2,2v per 6 cells=13.2 at full volts @ full charge, so your 10% is 1.32 volts. The alternator puts out up to 14.8 volts so your 10% will be 14.8 volts. 3X the max listed max of .500 volts. Better take up woodworking with hand tools

 

[Gr8ful]

A Bit More Proof 2% Voltage Drop Chart For 12 volt Systems
Maximum distance in feet of various gauge two conductor copper wire from power source to load for 2% voltage drop in a 12 volt system. Do not exceed the 2% drop for wire between PV modules and batteries.

Is 5% voltage drop too much?
Excessive voltage drop in a circuit can cause lights to flicker or burn dimly, heaters to heat poorly, and motors to run hotter than normal and burn out. It is recommended that the voltage drop should be less than 5% under a fully loaded condition.

What is the NEC recommendation for voltage drop?
The maximum total voltage drop for a combination of both branch circuit and feeder should not exceed 5%.
What is the formula for voltage drop in DC?

​

Jul 24, 2018 — Fire safety is based strictly on amps and wire gauge. Voltage drop is based on what the load will tolerate.
Here's the formula BTW. To calculate voltage drop use one of the three equations: V=R*I, if the flowing current and the electric element's resistance are known. V=P/I, if the power and electric current are known. V=V_{A}-V_{B}, if the voltage of two points is known.

 

[rruff]

What is the maximum voltage drop in a 12v circuit?

12V obviously.... is that a trick question?

A Bit More Proof 2% Voltage Drop Chart For 12 volt Systems

You keep talking about voltage drop rather than the thermal carrying capacity of the wire... after I've tried 3 times to explain it, and you don't even comment, just keep harping on something else...

 

[Gr8ful]

You haven't shown one fact or formula showing it won't start a fire. I've shown the charts, tables, calculations to prove my point. Quit being a truth denier. Case closed!

 

[Dirtrider]

You haven't shown one fact or formula showing it won't start a fire. I've shown the charts, tables, calculations to prove my point. Quit being a truth denier. Case closed!

I used 2 gauge for an 8 ft run to a 40A dc to dc charger. From everywhere I checked that would be a correct size.
I felt safe going with that size and it has worked great without getting hot at all.

 

[Gr8ful]

It's easy as the lower wire # the larger the wire size. The higher the Volts the smaller gauge wire you can use. I always go up (larger) one wire size larger than recommended. I had bought out a bunch of new left over wire from a job & had a roll of 12/2 wg I thought I'd never use but was putting in 10 400 watt metal halide lights in the hanger. You can tap into 120v, 208v, 240v, & 480v. I did 2-2 light circuits & 2-3 light circuits @ 240v & used my 14 ga wire up. So I have 4 switches for 10 fixtures so I can turn on 2 lights over the workbench in needed.

 

[tx2sturgis]

The charts that Gr8ful provided links to (in the other thread) have been relisted here:

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https://battlebornbatteries.com/battery-cable-size/
https://www.omnicalculator.com/physics/dc-wire-size
https://www.wirebarn.com/Wire-Calculator-_ep_41.html
https://mgispeedware.com/wire-size-chart/