15 replies to this topic

[eeae6000]

my first questions is this, the battry ground wire and the main power wire for starter, what gauge is it, if i had some 8 gauge laying around, would that be a upgrade or not big enough??


second questions is im going to be rewiring my whole headlamp and spot lamp aassembly with all new wires with relays and new switch, is 12 gauge good enough or should i get 10, 10 just seems so large

[dklawson]

It is unusual to hear someone on this board reference wire by its gauge. Regardless, 8 AWG is not going to be large enough for the main battery/earth cables for the Mini. I would consider nothing smaller than 2 AWG (35mm²). In the case of power cables, bigger is better, however, you must pay attention to the jacket size/diameter. If you are replacing the main battery feed from the rear to front of the car, you still need a jacket thickness that will fit in the track on the bottom of the car. In general stick with automotive wiring, not industrial power cable. However, finely stranded welding cables are also suitable for automotive use. Do not use any cable with coarse stranding of its multi-conductor copper core.

For the headlight relays, 16 to 18 AWG was good enough for the factory. 14 to 12 AWG is an improvement, 10 AWG is overkill and probably will not fit in your relay bases or fuse holders. The Ampacity of 14 AWG is nearly 1.5 times that of 16 AWG so it will offer a lot more current capacity while remaining fairly flexible and easy to work with.

[eeae6000]

ok, i ordered some 8 AWG and it is much larger then i expected, seems more like 4 or 2, i compared it to the stock ground on the mini battery and it is a bit bigger then the stock ground

i think i will go with 12 gauge then, seems like a good spot

thanks!!


by the way, how do you guys rate your wire size?

[Dan]

By the cross sectional conductor area. You aren't comparing the jacket size when you compare these cables are you? Two cables of different construction (number of cores or bundles of cores or weave for example) will look completely different even though they may have the same physical conductor size. You can't compare cables by outer diameter, you have to go by the given cable size. That's why they are never sold or specified simply by outer diameter. If you undersize the main battery cable or earths, if you are very lucky the car simply won't start. More likely you will start a fire.

[dklawson]

8 AWG will have much less copper than what is on the Mini now.

As Dan said, the appearance and size of the conductor (not the jacket) is highly influenced by the strand size and lay of the stranding. As a general reference, 2 AWG will have copper with a diameter close to 5/16" (about 8mm). For comparison, the copper in 8 AWG is close to 5/32" (4mm) in diameter. Again, this is highly influenced by the stranding. Regardless, #8 is smaller than #2 so something is not correct. Perhaps you are looking at the jacket diameter and not the copper diameter.

You asked how "you guys rate your wire size". Do you mean how/where did the AWG standards come from or something else?

[eeae6000]

im just sayings its 8 gauge because thats what seller said, the measurement of he actual wire (no jacket) is approx 1/4 inch

[eeae6000]

• and i ment how are wire size rated in the UK

is gauge and awg same thing?

[Dan]

Ahem, as I said :

By the cross sectional conductor area.

Expressed in square mm.

AWG = American Wire Gauge. When all things were imperial we used to have a wire gauge of our own over here, it wasn't quite the same as in the US though. We had SWG, Standard Wire Gauge.

[dklawson]

And if that isn't confusing enough, AWG is derived from Brown & Sharpe wire gauge.

Every European application I have worked on in my job has specified wire size by its area in mm² as Dan said. That is why I was surprised to see you were referencing wire by its gauge, and that is also why I gave you the 35mm² figure (for 2 AWG) in my first post.

[eeae6000]

im from the US, stationed in Germany, so thats why i used gauge, so would 1/4 inch inter size be good?

[dklawson]

According to the wire gage tables, #2 is nominally close to 1/4" copper diameter. However, that is really very dependent on the stranding of the copper. Most finely stranded #2 is going to be closer to the 5/16" size I mentioned above.

Something close to 1/4" will work, particularly if it is listed as #2 AWG or 35mm². As mentioned above, don't confuse this with the jacket diameter and if replacing the main cable to the front of the car, remember the cable still has to fit the track on the car's underbody.

[freshairmini]

I think the point is with wiring is what's important, is surface area. As electricity flows over the surface of a conductor.

So you could have a 1/4" cable (diameter) but with very thick wire stands. But compared to the same 1/4" cable with a greater quantity/fine strands you would have more surface area, so a more current could flow. hence why you need to buy wire that is graded by the proper standards, either american AWG or the british mm²

Am I right in saying that?

Edited by freshairmini, 29 February 2012 - 01:21 PM.

[Dan]

Yes and no, you are right about area being the most important thing but it's not surface area. It's cross sectional area as has been said above. Current travels through a conductor, not over it. The cross section of conductor at any point, including the cross section of contact in joints, is the most important point.

[eeae6000]

so smaller the strands the better?

mine prolly has about 20-30 strands in the 1/4 area

[SolarB]

so smaller the strands the better?

Not for this application. Smaller strands give greater flexibility but are more prone to corrosion.