Inverter Mystery..

You have a ground and also a chassis ground. If you tied the chassis Ground from the invertor it simply picked up the "-" part of the battery system.

If you did not have the invertor chassis tied to the truck frame then it would have not worked unless you had the Black wire tied to the truck frame or Battery "-".

https://www.lifewire.com/install-a-power-inverter-in-a-car-534683

 

double post

 

Inverter Chassis ground is tied to inverter Ground...

Any car/truck frame is tied to battery Negative unless you have an alt system hooking "+" to frame..

Sharing the negative battery lead to engine bolt with anything else or connecting directly to the battery negative post with anything except the block and chassis grounds is a terrible idea. Connecting electrical devices or hardware directly to a battery negative post is a bad idea (no matter who tells you to do it) unless the negative connection is 100% ground isolated at the electrical device. When an electrical device is directly connected to the negative post, if the negative post to block or chassis connection opens up or develops excessive resistance, the battery negative post will divert alternator or starter current through whatever is attached to the negative post. This can be hundreds of amperes! Very few devices and wiring will suffer a fault like this without permanent damage. It is also a fire risk.

https://www.w8ji.com/negative_lead_to_battery.htm

You might want to take electrical wiring 101 if you are not understanding this.. Google.

 

You are making it confusing... It is simple..

RED is Hot and goes to your Hot side of your Electrical system.

BLACK is Negative or ground and this is tied to your truck frame.

All cars/trucks are done this way. Go look at your car and you will see that the Negative of the battery is tied to the frame within a few feet of the battery.

Some cars are wired reversed but those are rare.

You will see in the truck the Black or Negative tied to other black wiring, but in the end it goes to truck frame.

Nothing should be tied directly to the Hot or "+" of the battery without an in line fuse. The Negative does not need an inline fuse.

 

@Mark Kling has it right. Its simple. Think of the inverter as simply any other electrical part used on the truck. Hook fused power to the inverter from battery positive, ground cable to the truck's frame. Then ground the case of the inverter to the truck's frame. Grounding the case is to protect you. If there is a fault and the case isn't grounded, the electricity could see you as the easiest path to ground. ZAP!!!

 

It only takes 100-200 ma to kill you... batteries put out Amps...

 

What do you want? Your questions have been answered time and time again. If you do not understand batteries and how they are wired in a car/truck I suggest you use Google and find your answers..

It is so simple .....