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Do you understand how electricity works?
Posted by LDH (more from LDH) on Tue, 1 May 2001 13:24:31
In Reply to: this is what you will need..., Jordan, Mon, 30 Apr 2001 17:39:32
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The only time I've ever heard of anyone running both power and ground to a trunk is when kids try their first amp install and don't read any instructions.
The reason we ground to the chassis is because it's convienient and has a very low resistance. See, the resistance of a wire is based on two things: it's cross-sectional area and it's length. The smaller the cross-section, the higher the resistance. The longer the cable, the higher the resistance. When we're moving large amounts of current, we want to have the smallest amount of that current eaten up by the resistance in the wire. That's why we use big wires for heavy loads. If the wire's way too small, the high resistance will waste much of the power, not allowing it to get to the component we're supplying. What's more, the energy wasted doesn't just disappear, it turns into heat. This starts fires.
The chassis is a huge amount of metal compared to a -02 AWG. While it actually has some resistance, it is pretty much nill as far as we're concerned. -02 wire has very low resistance, but not as low as the chassis. As I said, resistance depends on length. So what resistance is lower? -- Your 40ft of -02 AWG wire or 20ft of the same wire plus the almost nill resistance of 20 ft of chassis? That should be obvious now.
Also, 1" diameter cable is absoultely absurd. The reason you have to use it is because you have twice as much wire as you need. You make up for the higher resistance of longer cable by using thicker cable. For the rest of us, there's no reason to use any larger than 0 AWG. Honestly, 2 will work fine. As long as you make sure the battery is well grounded to the subframe, as is the engine, everything will be fine. The starter system on a Saab will draw less than 150 amps, which is well within the range for 0 gauge.
Anyone who has done some work in car audio would laugh out loud at 40 feet of -02 AWG wire in Saab, or anything for that matter. You'd need enough stereo equipment to level a building to justify that.
Posts in this Thread:
- Battery in trunk guys, What did you need to do the job., Mike 87 900s, Mon, 30 Apr 2001 13:00:18
- this is what you will need..., Jordan, Mon, 30 Apr 2001 17:39:32
- go to Painless Wiring, Chris F, Wed, 2 May 2001 00:07:51
- I'm inclined to agree with LDH..., TS, Tue, 1 May 2001 16:10:07
- Do you understand how electricity works?, LDH, Tue, 1 May 2001 13:24:31 <-- Viewing This Message
- 1" Diameter (750 MCM ???)copper cable is overkill, Tino, Mon, 30 Apr 2001 23:21:51
- Get cable from welding supply - welding cable n/m, Tcar, Mon, 30 Apr 2001 17:56:32
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