When to move from chassis to direct ground wire?

[Lasherž]

I'll admit I'm not likely to utilize this information but the google search for it is empty at the moment, so I'm curious if anyone knows.

How much wattage or amperage can go through a vehicle chassis before you start seeing voltage drops and/or heating? It's a steel frame and yet the voltage drop is often lower than that of a big wire, so I imagine it's quite a bit, but does anyone have experience of doing a build and suddenly realizing that your voltage drop is caused by the frame's limitation rather than just a certain grounding point on the frame or the ground wire running to the battery from the chassis/engine mounts?

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