Welding on a vehicle

[scrubber3]

I don't see where disconnecting the battery will do anything. It just wont. Sorry.... The only way to weld and avoid the problem that is on some of your minds is to take the ECU, BCU, and any other computer out of the vehicle before welding. Have fun with that. In the mean time, I will be welding on a yet another vehicle without problem. BTW, like I said before... I have been around literally thousands of vehicles being welded on problem free without even thinking about disconnecting the battery. I know so many other techs that have been around just as many vehicles as I have and we have never once been around a welder frying an ECU.

 

[BigAl]

Exactly. Difference in potential is what is going to cause the problem. The problem is massive current flow and the battery will allow it to flow through it. Battery not connected no current flow from the welder or induced voltage will go through the vehicles electrical system.

Still trying to wrap my mind around this...Isn't everything that is 12 volt in an automobile grounded to the frame. How would disconnecting the battery stop voltage from being back fed from the welder via the ground. I don't understand what disconnecting the battery would help. Maybe someone can use small words and explain this to me:sombrero: Anecdotally, I've never disconnected a battery and have had an issue.

 

[bfdiesel]

Anecdotally, I've never disconnected a battery and have had an issue.

What was the issue?

If there is no battery then everything will go to the same voltage (no path for current flow) on both positive and negative therefore no difference in potential.

The difference in potential backed by the ability to maintain it is how work is done by electricity. Think of voltage as pressure and current is the flow. A difference in voltage can cause a flow of current once the resistance (opposition to current flow) of the circuit is overcome. Everything being at the same pressure then there will be no flow.

A simple stick welder for instance has the difference in potential (pressure) between the work (ground) and electrode (welding rod) leads. Until they are connected in some way no current is flowing and no heat is being generated. Once the ground is connected to what is going to be worked on and the welding rod struck to it then the current starts to flow and the point in between with the highest resistance starts to get hot, how hot is varied by varying the flow of current. Ideally the point of the most heat is the tip of the welding rod being held at a small gap from the joint being welded.

This same thing can happen on a smaller scale with electrical components, all that is needed is enough flow through the circuit to to heat up and release the magic smoke from a component and once the magic smoke gets out there is no getting it back in.

 

[HillbillyfromAL]

The way I understand it unhooking the negative side of the battery ensures that the current flow from what ever your welding always travels from the gun to ground. If someone really wanted to test it don't connect the ground lead and try welding with the battery still connected. I take no responsibility for whatever breaks, or for a battery that catches fire

 

[hizen]

The way I understand it unhooking the negative side of the battery ensures that the current flow from what ever your welding always travels from the gun to ground. If someone really wanted to test it don't connect the ground lead and try welding with the battery still connected. I take no responsibility for whatever breaks, or for a battery that catches fire

Depends on if you are welding in DCEN (electrode negative) or DCEP (electrode positive) current flows from negative to positive.

 

[scrubber3]

You guys are trying to complicate something that is very simple. If there is no ground, there is no completed circuit. That is all.

 

[zidaro]

You guys are trying to complicate something that is very simple. If there is no ground, there is no completed circuit. That is all.

Thankyou, EXACTLY! Go with what works for EVERYONE. 4 pages?
I have welded on vehicles for years, i have always disconnected the neg. lead on battery, I have never had an issue. Doesnt matter which direction current is flowing, it needs a complete circuit- remove that ability

 

[scrubber3]

Also, if the vehicle has tires on it and nothing else besides the welder is touching it then you should not have an issue either way. Haven't you guys ever heard that a car is the best place to be during an electrical storm? I think that if there ever has been an issue with frying electronics on a vehicle then there must have been something grounding it out other than the battery cable or welder. A tool cart, air tool left attached to the air hose, transmission flush machine, a person, you get the idea right?