May I chime in here? when I was a teenager I was known by my peers for being that kid who built his own stereo power amplifiers from scratch (not kits).
Later for Magnolia Hi-Fi audio/video I opened staffed and trained installers for 6 new car audio install shops as I had 7 years full time of installing of electronics in 12volt vehicles already. Magnolia had never installed anything before they met me. After that I went into the repair service end of the business and ended up as tech services manager for NW Audio Video. Later I bought their repair shop and opened my own electronics repair shop which grew to 2 shops a dozen component level repair techs and between 50 and 60 chassis repairs daily when busy between the 2 repair shops. Did that for 12 years. Been around the electron block a few times. I know what breaks, what works and what works better. So over the years I have always been skeptical about "ampacity ratings" as they are published saying basically "oh yeah 10ga can carry 30 amps". Not so much in my opinion. Sure the wire won't catch fire if terminated properly, but there will be losses. Voltage losses to be clear. When you draw current (amps) through wire a voltage differential appears from one end of the wire to the other. The voltage drops as the current traverses the wire. The total voltage drop is equal to total overall wire Resistance (ohms) X Amps. (E=IR). Not a big deal if you can afford to loose some volts, say input 120 and deliver 110, or input 220 and deliver 210. But when you are starting out with only 12v then each volt becomes more prescious, because there are fewer to loose. My opinion. That is why Magnolia HiFi, before it's sale to Best Buy, always used 8ga for loads up to 20 amps and larger for 30 amp loads. The practice minimizes wire and terminal heating and minimizes voltage losses. We always did, and I still do, derate wire to a value less than what the ampacity chart says, by at least by one wire size. The practice results in better performance, higher reliability and longer service life. Cheers! jg Ps I use welding cable type wire for my engine connected alternator(s). It survives vibration better than most wire types and the cost is reasonable. The strands are very fine and the wire is extremely flexible. Great for high vibration applications. Strain relief and wire support are still a must. A second choice is type SO wire, it has similar flexibility, but to obtain single strands you usually have to disassemble a multi conductor SO cord. SO has high temp natural rubber insulation. SOOW has synthetic plastic and so does not do well in high temp applications but it is flexible.
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