This is true. I completely missed that you said you're running 3500w. If it's a true 3500w RMS, you'll definitely want to go with OFC, not CCA. Also, depending on how long your runs are, you may want to go with double 1/0 runs. If you're running from the front to a large battery bank in the back, you can do a single run of larger gauge welding wire, like 2/0 or 3/0, but it depends on your installation needs.