I made the mistake of connecting the negative first on my Laverda, 30 amp hour across my watch strap, through the spanner, and shorted to the frame. 😳 got hot real quick and welded the watch strap closed so I couldn’t get it off, had to rush inside and run it under the tap to cool down!
Won’t do that again☹️
That was nearly 40 years ago, still have the watch and it still works 😁