I'm using Matt's dual battery tray in my Taco.
Didn't get his kit, I built the rest of the system, but thought this tray was nice and worth the money since it's basically what I would have done anyway. I liked that the hold-down was made for an ML-ACR. Sometimes re-engineering the wheel isn't necessary. This is a pair of group 34/35 PC1400 Odysseys in place of a single group 27 OEM battery. Perhaps this would fit the Tundra?
Used 2 AWG primary wire for the starter, alternator and interconnections. I may rework the short wires between the batteries to use 1 AWG since I'm probably going to use that for the winch. Not that I intend to routinely parallel the batteries for winching, but just have a thing about uniformity. The starter and alternator don't need to be any larger. I'd use 1/0 AWG but it was just too heavy for the short positive leads. Any heavier than 1 or 2 AWG I think will require bending bus bar copper instead. There's only about 3 or 4 inches of cable between the crimps so it's got to be aligned and just the right length.
FWIW the rule of thumb is a battery cable less than 7 inches doesn't need a fuse. This is based on marine ABYC and Coast Guard guidelines, so for automobiles it's more about best practices than anything.
I didn't fuse anything that wasn't fused before from the factory, although I do plan to rework to add a twin fuse holder for the starter and winch when that wiring is done. I flip back and forth between thinking fuses are necessary and not, weighing safety vs. nuisance. Cutting a winch cable is bad but so would having a fuse open mid pull. Not worried on paper, a 300A fuse is going to let the windings in a winch motor melt before opening. I worry about corrosion and aging. Although I'm becoming more comfortable with those MRBF types, they seem to be holding up well. Guess I shouldn't be surprised being designed for saltwater marine use.
Bunch of technical stuff, ignore if you wish.
I prefer to rate 2 AWG for 170 A continuous (based on 30°C temp rise) and for safety I feel even a
300A MRBF is fine, which is rated at 200% for 60 seconds. Using welding cable with EPDM (rubber) insulation with max temperature of 150°C, 2 AWG will just reach 150°C at 616 amps for 60 seconds. A 2 AWG can hold a short circuit current (generally assumed to be 10 seconds) of 1,339 amps and a 300A MRBF will open well below this current, 350% or 1,050 amps, in a maximum of 1 second. None of this assumes any cooling (except for the continuous). Still, I prefer a max of 225A MRBF for 2 AWG to give a margin, so a 200A breaker is probably a good choice. For example, a
Cooper 187 series will open at 200% between 10 and 40 seconds, 300% between 5 and 12 seconds.
