Not understanding the difference in amp draw and wire size 12v vs.120ac

[moneypit]

Now coming from an electrical background in commercial and residential im not makeing the connection. It didn't matter if it was 120,240, or 3 phase 480, 200 amps required a to 2/0 wire. Which depending on insulation is rated at 200 or 225. this is not including calculations for any kind of voltage drop. How is it that 1/0 is recommended for a 12 volt system for 200 amps. Is there math at work im not familiar with dealing with 12 volt systems.

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[T3mpest 10+ year member]

How long of a run is an average home wire like that? In a car we are only dealing with 20 feet or less, which is the distance they rate the wire for, hardly enough to get out of one large room in a home.

 

[jrdnhsnbrg 10+ year member]

Now coming from an electrical background in commercial and residential im not makeing the connection. It didn't matter if it was 120,240, or 3 phase 480, 200 amps required a to 2/0 wire. Which depending on insulation is rated at 200 or 225. this is not including calculations for any kind of voltage drop. How is it that 1/0 is recommended for a 12 volt system for 200 amps. Is there math at work im not familiar with dealing with 12 volt systems.

True 1/0ga car audio wire has high strand count for fexibility, I don't know if it has any more of an effect of how well it is able to carry current. Typically in car audio you won't have runs of wire much longer than 20ft where with residential and commercial wiring it is VERY easy to have runs of wire MUCH longer than 20 feet as I assume you know. Smaller wire can carry a lot of current over a short distance.

 

[UsAmpsFreak]

Now coming from an electrical background in commercial and residential im not makeing the connection. It didn't matter if it was 120,240, or 3 phase 480, 200 amps required a to 2/0 wire. Which depending on insulation is rated at 200 or 225. this is not including calculations for any kind of voltage drop. How is it that 1/0 is recommended for a 12 volt system for 200 amps. Is there math at work im not familiar with dealing with 12 volt systems.

I'm not too up on the actual terms for this but in my teachings the way i understand it is for example they type of current ran through the lines in a power grid is a different type of current than is ran in vehicles. It isn't dependant on huge gauge when running long runs of wire. From a car battery if you were to run a 100 ft run of cable, the amount of loss and resistance you would have in a run that long you would need to have a mammoth size of cable and would have atleast 1 volt difference from the battery to the end of the wire. I'll let someone else that knows the technical terms for this to explain with more facts than i can.

Doesn't commercial grade cable use one strand of solid copper or something versus car audio wire which is many strands? I bet that is the main difference.

 

[jrdnhsnbrg 10+ year member]

I'm not too up on the actual terms for this but in my teachings the way i understand it is for example they type of current ran through the lines in a power grid is a different type of current than is ran in vehicles. It isn't dependant on huge gauge when running long runs of wire. From a car battery if you were to run a 100 ft run of cable, the amount of loss and resistance you would have in a run that long you would need to have a mammoth size of cable and would have atleast 1 volt difference from the battery to the end of the wire. I'll let someone else that knows the technical terms for this to explain with more facts than i can.

Residential and commercial wiring use AC current where our cars are purely DC (besides the outgoing amp signal). When you get up in the range of 120V a 5V drop isn't that big of a deal, where if you dropped from 14.4 to 9.4 in your car you'd flip shit and wonder what the heck is going on

 

[basswiigee]

all wire all sizes have different strand count and recommendations for wattage/amps tolerable...

 

[moneypit]

Aha so it the actual construction of the wire and probably its insulation on top of the short runs that you would do with it. Gotcha thanks guys

 

[keep_hope_alive Premium Member]

Aha so it the actual construction of the wire and probably its insulation on top of the short runs that you would do with it. Gotcha thanks guys

THHN/THWN is made to very specific standards and ratings. car audio wire is NOT. you will see 10 brands and 10 different constructions/strand counts/strand AWG/ insulation material/insulation thickness/etc. even actual AWG will vary between brands for the same labeled wire. Some 1/0 is good for 300A, some for 200A. the 200A wire you saw is probably CCA or copper clad aluminum - so you are actually comparing against aluminum wire ratings.

to others - THHN is stranded but the strands are much thicker making the wire much harder to bend.

 

[jrdnhsnbrg 10+ year member]

THHN/THWN is made to very specific standards and ratings. car audio wire is NOT. you will see 10 brands and 10 different constructions/strand counts/strand AWG/ insulation material/insulation thickness/etc. even actual AWG will vary between brands for the same labeled wire. Some 1/0 is good for 300A, some for 200A. the 200A wire you saw is probably CCA or copper clad aluminum - so you are actually comparing against aluminum wire ratings.
to others - THHN is stranded but the strands are much thicker making the wire much harder to bend.

One time I got some 6ga wire from a teacher at my school who had it left over from installing something in his garage, it was like 6 strands or something and was a royal PITA to work with. It always wiggled out of both crimpable ring terminals and set screw ring terminals.