Use vehicle chassis as inverter negative conductor? Pros/Cons

[apctjb]

Installing a 1000W inverter in my pickup truck (12V-100A max)) which will connect to my trucks starting battery. I was intending on using #4AWG cable for both positive and negative conductors (about 20' run from batter to inverter location) but ran across an article indicating it would be better to use the chassis of the vehicle as the negative conductor rather than running a separate negative conductor all the way back to the battery post. In other words the negative terminal of my inverter would connect to the chassis at the inverter, and the chassis to the battery terminal and the frame of the vehicle would be the conductor. I would use #4AWG to make the chassis connections

Good idea or bad?

Apologies if this topic has been covered previously, I am in a hurry to finish the install. Thanks

 

[time2roll]

For 1000 watts I would use the chassis frame for negative.

 

[apctjb]

For 1000 watts I would use the chassis frame for negative.

Thanks for the reply. Is there an inverter size/amp draw cutoff where you would advise against using chassis frame as a conductor? Just curious to understand.

 

[richard cabesa]

Circuit Wizzard says 2/0 cable for that load and distance. Remember you have to count there and back counting frame or wire it’s part of the circuit.

I don’t know how to figure if your frame rail is equal to a 2/0 wire.
Any way to mount the inverter much closer to the chassis battery. Maybe under the dash? You could then run easy to work with wire size to the rear

 

[time2roll]

Thanks for the reply. Is there an inverter size/amp draw cutoff where you would advise against using chassis frame as a conductor? Just curious to understand.

You are competing with other systems that are grounded such as the starter motor. I think 100 amps is plenty of extra. If going 2000 watts I would want more battery and not run 20' to the inverter with 2/0. So 1000w install would be my max before going with a more complete installed system.

 

[grizzzman]

Good grief. Most frames prepped correctly will do just fine as a ground path. I would suggest adding a cable from Alt/Battery negative to the frame. And if concerned preform a voltage drop at the max amps you plan to use.

 

[Mcgivor]

Personally I would never use the chassis as the negative and secondly I wouldn't use the starting battery to feed an inverter for anything other than short duration use as the battery nor the chassis intended or designed for the purpose.

 

[apctjb]

The article I mentioned that prompted the question suggested that installing a large conductor directly to the battery terminal was a very bad idea and could result in unintended current flows as the inverter negative cable might end up being the lowest resistance path to negative for other loads (like the starter). Hence my question...

 

[time2roll]

No electroencabulator needed to protect the dimodial back feed on the muffler bearing or blinker fluid.

 

[12VoltInstalls]

The article I mentioned that prompted the question suggested that installing a large conductor directly to the battery terminal was a very bad idea and could result in unintended current flows as the inverter negative cable might end up being the lowest resistance path to negative for other loads (like the starter). Hence my question...

That makes no sense - don’t trust that article. The starter is grounded to the block which is grounded through the alternator and/or battery.

Personally I would never use the chassis as the negative and secondly I wouldn't use the starting battery to feed an inverter for anything other than short duration use as the battery nor the chassis intended or designed for the purpose.

Most frames prepped correctly will do just fine as a ground path.

The amp capacity of the cable from battery or block to chassis needs to be addressed. Maybe it’s ok, often it’s not.

There’s ways to safely use the frame as a ground point.
i, however, prefer fused home runs from battery to inverter. And 4ga is too small imho for what your doing. A 1000W inverter is 2000W surge which is ~165A nominal. Never mind voltage drop. My opinion anyway.

 

[grizzzman]

No electroencabulator needed to protect the dimodial back feed on the muffler bearing or blinker fluid.

This what you mean?"Turbo Encabulator"

 

[carlrx7]

I had the same question, this video makes it pretty clear.

-cb

 

[Mcgivor]

The article I mentioned that prompted the question suggested that installing a large conductor directly to the battery terminal was a very bad idea and could result in unintended current flows as the inverter negative cable might end up being the lowest resistance path to negative for other loads (like the starter). Hence my question...

Using a secondary deep cycle battery dedicated for the inverter is by far the better way to go, almost 80% of vehicular breakdowns are electrically related, 80% of the electrical problems are chassis negative bonding related, having a potential 100A draw seeking the party of lowest resistance is a recipe for disaster, particularly where sensitive electronics are involved.

 

[Stepandwolf]

No electroencabulator needed to protect the dimodial back feed on the muffler bearing or blinker fluid.

Not to mention the nematode flyback oscillator.

 

[time2roll]

This what you mean?"Turbo Encabulator"

That one is for the transmission. This for the electronic devices...

Electro Turbo Encabulator