Nope, not normal, it's indicative of a fried R/R, best to replace the R/R , battery and repair the wires and plug if melted.

Check the battery to see if the electrolyte has boiled off - which is why I mention potentially having to replace the battery

Best not to put a new R/R in with a nicely cooked battery resulting from a bad R/R - best practice is to replace both.

 

Don't forget to check the stator for a short to ground as well.

 

Thanks for the replies, guys. The stator checks out OK. Oh well, there goes the after-Christmas budget on an R/R and battery...