Snowbird, That's what I was going to mention, If all your disconnecting is the battery your kidding yourself thinking that all you need to do.

There are several different grounds that should be included to isolate the electrical system.

I have been welding on trucks, heavy equipment, conveyors, buildings and everything else under the sun for the last 26 years.

I never disconnect the batteries, I just keep the ground hooked up next to me.

Even on buildings, If you don't keep your ground with you, You can catch a ground on a water pipe or building column and heat the ground up inside the wall that will then burn anything that is combustible.

You always need to keep your ground with you in these types of situations.