Andonso1

Any suggestions for a location to drill a hole(s) in the firewall?

I need to run a couple of 1/0 battery cables (pos+ / neg-) through the firewall on the passenger side or near the center. (97+ XJ).

I would like to drill a separate hole or holes and protect them with a grommet and some sort of sealant or caulking as waterproofing and keep the wiring in the upper part of the engine compartment and firewall if possible.

CrawdadSlim

There's a factory punch out in the firewall drivers side center. What's the negative for?

Andonso1

Ok, thanks I will look for a punch out. I am not sure what the negative is for.

CrawdadSlim

You know what It's just to the right of the master cylinder.

Andonso1

There are oem and aftermarket wires (#10, #12 and smaller) running through a knock out between the fender and brake booster. Not sure if there is enough room for a larger cable, its sealed up with silicon.

I want to run some 1/0 to the passenger side and was hoping there was somewhere to drill hole(s) through the firewall, (passenger side). The heater assembly and venting block clear access to the firewall, takes up most of the space on the passenger side underneath the dash. I don't want to drill into the heater assembly, other tubing and wiring.

Possibly a cable could be run through the passenger side harness knock out if it could be enlarged. I am looking around for a clear shot to drill without compromising the heater and needing to remove the dash board.

CrawdadSlim

Find a likely spot and drill a small pilot hole. Shove a stick or staw through it and see where it ends up.

Andonso1

I was thinking about doing something similar but thought someone from the forum might know a more specific spot or area on the firewall they have already drilled.

If I can't find a more specific area then I will most likely remove the dash and loosen up the heater assembly, find a spot to drill, route the cables, grommet, and seal up to prevent any water and moisture leakage.

5-90

For what? You're best off using a "pass-through post" to keep from having to worry about chafing of the wire jacket, but they're limited in current carrying capacity (150-200A, or so.)

As far as the earth? Unless you're dealing with some really heavy loads, using the chassis should do.

You probably don't need 0AWG wiring, either - so you could save a decent amount of money, if you chew on it a bit.

Please advise.

Andonso1

Pass-through post sounds like a good idea, but there needs to be an unrestricted area to pass-through.

I have some existing 1/0 (black & red) welding cable, that's not being used for anything. It could probably use some additional jacketing when running in the engine compartment. Not recommended for permanent installation close to a hot engine, around dripping hot oil, gas, etc. I would think it should work ok when installed e.g. along the top part of the fender well using some convoluted tubing as additional sheathing.

I am looking to use a min. 1/0 cable as sometimes a HD 2000/4000 watt inverter is connected for things such as power tools, etc. It's heavier and larger than similar wattage inverters, uses a recommended min. of 2/0 cable. (carried when needed.)

Potentially there would be a maximum 400 amp draw from the inverter to the second battery, connected to the car battery and alternator.

Alternator == (starting battery) == (fuse) ====1/0 ===(isolator)=(fuse) == (HD marine battery) == (fuse) ==2/0== (inverter)

However the recommended vehicle installation would be to isolate the main battery from the second battery at the alternator. Another type of isolator would be required, such as a solid state isolator, cost is more than a $20.00 ~100 - 200 amp mechanical isolator.

alternator ==== (isolator) ====== (marine battery)=(fuse) = inverter
----------------------------||======= (main battery)

Andonso1

...

CrawdadSlim

Buy a generator.

Andonso1

Right now what I'm trying to do is upgrade the smaller cable to a 1/0, where the second battery can be used as a starting battery if the main battery goes dead as well as powering and recharging other devices.

Once a batteries reserve goes below a certain percentage the recovery time becomes much longer.

Simply by increasing the cable size can significantly increase a battery systems efficiency and reduce vulnerabilities.