I too had been using the Battery Tenders for many years without any issues.
But finding the shorted unit with the melted case was a wake-up call for me.... eek
The Battery Tender is assembled with many internal components from China, and my basic question is why don't they design in an internal circuit breaker in case the unit shorts out.
This will shut down the unit as to prevent a possible fire..

Just my $0.02.. wink