Left an 18v XR battery in the charger last night, in the barn. It went
down into the 20s. Today I went to change batteries and it was stuck in
the charger. I finally got it pried out and there was a smell of burnt
plastic and the battery and charger were both partially melted, to the
point that another battery wouldn't fit into the charger and the charged
battery wouldn't fit into any tool I had.

Noticed that the charger is marked "do not use below 40F". Either
they're real serious about that or the charger picked last night to die.

Went down to Lowes and got a couple of new batteries and a new charger
for going on 180 bucks after tax. Was tempted by a cordless drill which
with two batteries and charger was 129, but they were the smaller
capacity batteries, the charger was the older design that doesn't do
NiMH or Lithium ion, and I already have a better drill.

Be interesting to see if the new charger resurrects some of the
batteries that the old one said were dead.