Wire guage safety?

[YEOJ]

According to this chart:
Ampacity Charts

10ga copper wire is only good to 30A... does this mean I need to build a box mod with 8ga wire if I plan on using builds that draw a potential 35A?

I'm curious to know because I want to start building my own box mod and I want to be as safe as possible....

 

[gandymarsh]

That chart is for 110/220 Volt AC circuits that run for a considerable length of time. I don't think the same applies to low voltage circuits that only run for a few seconds. Disclaimer: I'm not an electrical engineer or even close. Most modders use 14 gauge or even higher (number wise) wire in their mods.

 

[YEOJ]

Ok cool thank you. Do you know if there is a performance difference when it comes to braided or single strand wire?

 

[gandymarsh]

Solid wire will perform better, stranded wire is more flexible.

 

[JimmyDB]

The heating of the wire (safety) has to do with the amps and it's called Joule heating. It's [dang near] the same for 110/220 60Hz AC as it is for 4.2V. You will get [dang near] the same voltage drop as well. The main difference is that we are using it in short bursts... so long term heating of the wire isn't an issue... but the voltage drop is still an issue and in our case, a bigger issue.

 

[Visus]

It all depends on your finger size if you have bigger fingers than you need to use huge wire and smaller than use...,.

Now not to be confused with actual swap positions of lefty righty then thats a whole different solar system..

Because mods arranged so close in runs less than 5" then no worry at 14ga and up @ ~50A

Solid wire leagues better than stranded but needs routing pre-thought and use of even 18ga would be more than specific @35A

Pipe dreamers give huge vape numbers and whoa at even 100wattages overwhelmed by old desires being silly
unless ur a cracky then IDK what wattage ya need.

 

[Poisontail]

8 gauge lol that about the size of a pencil

 

[Norrin]

You also have to consider the lengths involved, which makes it basically a situation where just use the thinkest wire you can for what you are doing, but even 20g will do most of the time because of the really short lengths.

Not suggesting using 20g here just saying it is usable if no option because of space.

 

[JimmyDB]

So... what';s the voltage drop for 14AWG solid copper wire pushing 4.2V at 50A... with a total path of 6"?

or 18AWG running 35A at 4.2V?

 

[Visus]

At 6" the wires resistance is
Wire Resistance: ~0.0015 ohms
@54A The wire will draw ~2.9watts and sag @ ~0.05477v
Its your switch, the 510 connector @ atomizer, atomizer metal, solder joins, ambient temperature, battery resistance etc etc
the 14ga wire is more than capable to give ya a sag free vape, its everything in between..

 

[JimmyDB]

At 6" the wires resistance is
Wire Resistance: ~0.0015 ohms
@54A The wire will draw ~2.9watts and sag @ ~0.05477v
Its your switch, the 510 connector @ atomizer, atomizer metal, solder joins, ambient temperature, battery resistance etc etc
the 14ga wire is more than capable to give ya a sag free vape, its everything in between..

That's the info for 10AWG, right, cause that's what I would get for 10AWG @ 54A with 4.2V. I admit 54A is quite a bit of power though... I think 6" is fair for the total path of wires going from a battery to mosfet to atty etc.

14AWG / 54A / 4.2V @ 6" -> 70mV drop ~> 3.5W loss
18AWG / 54A / 4.2V @ 6" -> 177mV drop ~> 9.5W loss
20AWG / 54A / 4.2V @ 6" -> 282mV drop ~> 15W loss

14AWG / 20A / 4.2V @ 6" -> 26mV drop ~> 0.5W loss
18AWG / 20A / 4.2V @ 6" -> 66mV drop ~> 1.3W loss
20AWG / 20A / 4.2V @ 6" -> 105mV drop ~> 2.4W loss

I totally agree that the wiring is only a portion of the total losses to deal with, and I don't generally see the gauge as a safety issue considering the short time frames we are working with and given common sense

For me, it's partly about the voltage lost before it makes it to the 510... that's just lost power. What's weird, is I keep seeing examples where someone just measures the no-load voltage at the 510... as though that is indicative of what happens under loads.

UPDATE: Losses have been updated

 

[Visus]

That's the info for 10AWG, right, cause that's what I would get for 10AWG @ 54A with 4.2V. I admit 54A is quite a bit of power though... I think 6" is fair for the total path of wires going from a battery to mosfet to atty etc.

14AWG / 54A / 4.2V @ 6" -> 140mV drop ~> 7W loss
18AWG / 54A / 4.2V @ 6" -> 355mV drop ~> 19W loss
20AWG / 54A / 4.2V @ 6" -> 564mV drop ~> 30W loss

14AWG / 20A / 4.2V @ 6" -> 52mV drop ~> 1W loss
18AWG / 20A / 4.2V @ 6" -> 132mV drop ~> 2.6W loss
20AWG / 20A / 4.2V @ 6" -> 209mV drop ~> 4.2W loss

I totally agree that the wiring is only a portion of the total losses to deal with, and I don't generally see the gauge as a safety issue considering the short time frames we are working with and given common sense

For me, it's partly about the voltage lost before it makes it to the 510... that's just lost power. What's weird, is I keep seeing examples where someone just measures the no-load voltage at the 510... as though that is indicative of what happens under loads.

Solid gauge was what I used in the calculator not stranded they had different figures you said solid
Another factor that will change the outcome is if you wire with no insulation. Many variables..

If you use the wires resistance @ 54A @6" you get what I posted lol
Not considering voltage just the wire@ 54A you will never get close to 4.2v @ 54A in a mech
without a huge battery array lol..

 

[JimmyDB]

Solid gauge was what I used in the calculator not stranded they had different figures you said solid
Another factor that will change the outcome is if you wire with no insulation. Many variables..

If you use the wires resistance @ 54A @6" you get what I posted lol
Not considering voltage just the wire@ 54A you will never get close to 4.2v @ 54A in a mech
without a huge battery array lol..

Right, so that was based on 10AWG solid copper which has a circular mils of 10380 with a resistance of 12.9/cir mil foot at 167F with a generally accepted correction factor of 1.0 for common 'room temp'.

I agree 54A from even a few common (18650 and the like) batteries without significant sag is unreal. I introduced 50A (not 54A) at the same time I introduced 35A just in asking what the Vd was. I figure 20A is much more reasonable and that's why I listed the 20A drops of common wire sizes. Looking back though, I probably should have included 35A info as the OP was asking about 35A pulls in a box mod. I would personally try to stick with a Vd of 2% or less at the highest voltage level... 4.2*0.02-> 84mV.

10AWG / 35A / 4.2V @ 6" -> 18mV drop ~> 0.63W loss
14AWG / 35A / 4.2V @ 6" -> 45mV drop ~> 1.6W loss
18AWG / 35A / 4.2V @ 6" -> 115mV drop ~> 4.02W loss
20AWG / 35A / 4.2V @ 6" -> 183mV drop ~> 6.4W loss

Agreed, many variables even right down to the heat dissipation capability of the wire (insulated or not) including the case itself... splitting hairs at that point in how much it will have any noticeable effect... might as well start talking about making the copper black so it can dissipate heat better if we go any deeper down that road of these details

Which calc were you using? I would like to check out the source and see how it compares to the NEC values, etc.

UPDATE: losses updated.

 

[YEOJ]

Y'all are getting way too technical... so 14ga is safe? Ok cool, I'll use that haha

 

[JimmyDB]

Y'all are getting way too technical... so 14ga is safe? Ok cool, I'll use that haha

I wasn't really concerned with the general 'safety' of 14AWG... I was concerned with the voltage drop and how that would effect the output power... I figure if someone is making their own box, they probably don't want to lose a chunk of power simply due to cheaping out on the wire. As I write my own calc, I'm starting to think this other one was off by about a factor of 2 when I compare the results to what I see in Ugly's.

 

[Dampmaskin]

If it was off by a factor of 2, maybe it assumes that you have two wires in series (plus/minus), in other words a separate wire for the return current so to speak.

 

[JimmyDB]

If it was off by a factor of 2, maybe it assumes that you have two wires in series (plus/minus), in other words a separate wire for the return current so to speak.

That's what I'm thinking as when I was doing it by hand, that's how I would do it. Thank goodness for an Ugly's sitting around

 

[Visus]

Which calc were you using? I would like to check out the source and see how it compares to the NEC values, etc.

UPDATE: losses updated.

Just used ohms law 54A X resistance lol Using the wire as a coil rudimentary mental was close lol

Ohm's Law Calculator