What did you do to LED a 1W casio diode? ESD? :thinking:
I've seen these take 2A+ and still live.
But this behavior is normal for these diodes. I thought it was abnormal because I thought you were talking about a 660nm diode.
Compare yours with the measurements I took off one of mine in this thread. You'll probably find the the voltage and current numbers for yours are fairly close to mine if it's electrically intact.
You have it backwards. It's still a diode in the circuit. As voltage increases, it's resistance increases. That's why the voltages don't really change that much compared to changes in current.