1/0 wire with lugs through the firewall

I'm trying to route a 1/0 cable through the firewall. It is running from the battery, through a separate 150A fuse above the fuse box, to a bus bar on the back wall of the cab. I plan to have Polar Wire pre-crimp two 5/16" lugs onto the ends, and install heat shrink. The OD is about 0.55". My guess is the lug will not be much larger than the wire OD.

I've seen lots of threads for smaller wires, but nothing this large. What do people recommend for putting this wire through the firewall? Any other routing tips? I was going to route across to the center of the truck and run it back over the hump in the floor, under the shifter and e-brake area.

 

Seeing as your destination is the back wall of the cab perhaps you could run the wire under the cab and through the floor or through the back wall itself.

How about insulted bulkhead connectors:

 

i've done 1/0 in all my vehicles for stereo equipment, just haven't done the taco yet, planned for this summer.

there's the fancy bulkhead connectors rusty pointed out, but the disadvantage there is that it's an additional connection point, which can create additional failure modes.

i make my own cables. the ends, hydraulic crimpers, and adhesive-lined heatshrink is quite cheap, and allows for a much more custom installation than dealing with ordering specific sizes and then realizing it won't work as intended.

TEENO Hydraulic Crimping Tool 10T Hydraulic Cable Lug Crimper 12 to 2/0 AWG Hydraulic Hand Crimper Tool Electrical Terminal Cable Wire Tool Kit with 9 Die

https://www.amazon.com/Hydraulic-Crimping-TEENO-Electric-Terminals/dp/B0B312RF9G

$9 Sanuke 10pcs 1/0 AWG-3/8 Battery Lugs, UL Listed Heavy Duty Wire Lugs Ring Terminal 0 Guage terminals Battery Cable Ends/Terminal Connectors with 3:1 Heat Shrink Tubing

https://www.amazon.com/Sanuke-Terminal-Connectors-0Guage-3-Electrical/dp/B083QC122B

in every vehicle i've wired so far, there's always a main wiring grommet through the firewall with ample space to the sides. i normally cut an 'x' in the side of the grommet with a new razor blade, just making the cuts smaller than my wire diameter. i'll pull through what i need, and the rubber grommet self-seals behind it.

there's also typically rubber grommets in the floor that allow access closer to the destination point at the rear wall. my last truck, i followed the frame rail back from the battery, under the cab, and came up under the seats through one of those factory plugs to get to the back wall.

there's also rubber cable glands that some have used to drill a hole in the firewall--just verify the diameter of your specific 1/0.

$9 AMPELE 2 Pack 1-1/4'' NPT Cable Gland Waterproof Adjustable 18.5-25mm/0.73-0.98" Nylon Cable Glands Joints with Gaskets (1-1/4", 2 Pack)

https://www.amazon.com/AMPELE-Waterproof-Adjustable-18-5-25mm-0-73-0-98inch/dp/B09PVJR526

i've run into drastic differences between brands cable sizing. this isn't the worst offender, but are 2 different brands of 1/0 i had on hand a while back...



i've been sticking to knuconceptz for my wire because it's consistently sized correctly. other's, i've gotten "1/0" that is really 4ga...

and also be sure that you're getting pure copper or copper-tinned wire, not CCA wire. it's crap and should be banned, but halves the cost, so many people buy it for the price point--if using CCA wire, you need to step up 1 gauge to deal with the additional resistance, which most people don't do.

 

This is what you’re looking for:
https://mavenspeed.com/collections/b2t-engineering/products/radlok-connector-bulkhead

 

Hey OP! I'm actually in the same boat planning out my new wire runs and already have 2 AWG running through the firewall. My advice, don't go through the firewall with that large of wire. Let me explain.

1/0 is a very large wire, I only had 2 awg and could only fit my positive wire along the door tracks. and the carpet on the center hump is very tight and barely fit my two runs of 14/2 to my radios.

You stated you're running the wire to your back seat to a distribution setup (so just like I had initially but am replacing properly). In the back of the the cab right underneath the storage panels (the ones held on with 10mm bolts) is a LARGE roughly 2.5" grommet you can run through. It fits two 2 AWG cables easily and can even fit 2/0, so your 1/0 will be fine.

I'm only using 2 awg as its max 100A with tolerable voltage drop up to 10% for DC-DC charging otherwise I would use large gauge wire