The charger failed to even turn on after the leads were momentarily connected in reverse polarity to a mostly discharged battery.
I found the 50 amp output fuse right away but it was still good. After checking a few items out I observed some components tucked into slots near the center core of the transformer. The leads were long enough to pull these components out and one appears to be a 2.5 Amp fuse along with a 150 degree centigrade fuse. I jumpped this item with a green clip lead and all worked.
I did not bump into this device on the DigiKey web site so purchase a 3 amp package of auto fuses and installed one across the leads.
All worked until I tried the 30 amp position. I had the charger hooked up to my charged car battery for this test. The fuse blew so I replaced it with either a 10 or 15 amp auto fuse. This time the fuse held for all tests.
(The above is the inside view of the charger.)
I seldom jump the fuse up so high from original but I figure the house circuit will be protected and if the charger blows, fine. Get a new charger. We don’t want a good charger to fail due to a fuse especially a fuse hidden inside the box.
Note - since the charger is running of 120 vac and then converts this ac voltage to only 12 vdc the input amperage will need to be only 1/10 or so of the rated output.