I was trying to charge up my bike batteries. And I got the connections wrong. As a result, 50 amps tried to go down a wire rated for less than one amp. There was grey smoke, and then blue smoke, I realised that I'd done and pulled the connections apart, but by they they were really hot, and I have a burn on my thumb and first finger. They'll heal.
The good news is that I don't seem to have damaged anything important, the thin wire acted as a fuse.
Even better news; all my bike batteries are still good, and so are at least six of the chargers - I'll check the others tomorrow And I inflated the tires of my three best bikes, and they seem OK.