Welding brackets on tractor frame

[LouNY]

I had been told to lift the battery ground connection before welding on any vehicle long before the internet was even a dream.
I have usually lifted the ground cable(s) and have seldom ever had an issue. I did lose a generator one time, was that coincidence or not no clue but it was working before I started the repair and wasn't when I finished the initial repair. Replace the generator and the system worked again.

 

[rScotty]

Seems like there are several opinions. Here's mine:

It doesn't take long to disconnect the battery.

 

[ruffdog]

My Bobcat manual says to disconnect the battery AND unplug the computer before welding.

 

[rScotty]

My Bobcat manual says to disconnect the battery AND unplug the computer before welding.

Good on them.

 

[5030]

I never do but again, I keep the current path as close to the weld point as possible. 20 years and no issues but then my units aren't electronic controlled either. If they were, I'd probably unplug everything anyway.

Welding current will always take the shortest path and least electrical resistance, no exceptions.

Only takes me a second to disconnect them anyway. I have battery isolators on all of them as a theft deterrent when I leave them in the field. Insert key, turn and pull and no circuit.

 

[SylvainG]

And if your FEL and implement isn't on the ground, then there is no current. Tires are pretty good insulators.

 

[Sberry]

What? Feel free to explain that and any real explanation as to how unhook helps anything would be read.

 

[Sberry]

I think some simply put that in manuals as a disclaimer and the guy wrote it doesn't know any more about it than the janitor does.

 

[Sberry]

Think about how a car or truck is wired. If welding current could go thru a battery it would need to be shorted. The world would come to a stop if everything with electronics had to be disconnected.
Couldn't use trucks for welding platforms, the guy with the big Cat service truck has a weld vise on the bumper. Look at all the pipeline rigs, brandy new 1T, north of 70k and welding on the beds. My own, welding work lead bolted to the frame/body bumper.

 

[rScotty]

What? Feel free to explain that and any real explanation as to how unhook helps anything would be read.

I think what he is saying with the tires as insulators and potential paths through FEL and 3pt attachments touching the ground you have a real situation.
I agree, and here is why:
The ground clamped on the welder frame and the electrical supply ground SHOULD be at the same potential if all the grounds and neutrals in the supply circuit and in the welder are connected correctly - but that doesn't mean that they are.
And if they are not, then the potential to ground is not absolute, it is relative. And we know that current can flow between two dissimilar "grounds".