R_W_B
Senior Member
Glider's statement about the negative batt lead off first and on last is good practice. If you don't follow it; you will eventually let the magic smoke out of the electrics and make yourself unhappy.
Plus one on that, the reason you need to take the neg off FIRST is that the electron current flow runs from neg to pos. So if you take the pos off first and let it hit a ground then you have destructive current flow quickly.
You can still get a spark even taking the neg cable off first IF you dont move it away quick and clean, But as soon as the neg cable is moved away from the battery all possible current flow is stopped at the neg terminal of the battery.
I always put masking tape over my neg terminal just in cast the cable (or something else) happens to get knocked back into the terminal. One of my most exciting moments was once on a car battery I dropped a wrench across both battery posts. I had to knock it loose it got so hot so quick.