Wire Gauge

Started by Frank M, July 26, 2023, 07:48 AM

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Frank M

Need to replace the wire that runs from the 12v 40 amp circuit breaker in the battery compartment back to the converter on my 73 dodge Brave. Anyone have any suggestions on what gauge wire I should use?  I am thinking 8 gauge or 10 gauge should work. Thanks


It depends how you want your system to work. Do you want it to work like in 1973 or like 2023.

When your wiring is to thin you only create resistance and you can get something like this.

Aircon wiring.jpg

Now clearly something went wrong here in the specific area, but I guess you'll get the picture that this really is something you don't want.

As the wiring is for your inverter (so a main power source) to a 40 amp breaker switch you would want as less power loss as possible and you certainly don't want to create heat with your wiring so I would advise you to use double zero gauge wiring, based on underneath calculations.

Wire gauge calculator.jpg

You can find the Calculator here

All these figures matter so fill them in to you specific needs.

And of course, as you are handling your wiring yourself, following this advise is at your own risk.  ;)


The above voltage drop percentage is set at 1 percent. 3 Percent is allowable and within reason. Also, 200 inches is 16 plus feet...so your inverter/charger would be on a trailer behind your RV :D. Mine is less than 5' so a 40amp load at 12V with a 3% max voltage drop would allow me to use a 8awg or even a 10. You do need to use good practices and use good wire and connectors or you should upsize your wire size to make up for lousy work. 2/0 is an amazing size wire for a 40amp anything in an RV. I have 2/0 for my 160 amp alternator to my batteries at 7' and has 1.67% voltage drop..excellent. 
72 Brave..resto mod - Disk Conversion - Diesel Heater - Air Bags modified to fit - 318 Holley Sniper