Start Battery fuse blowing

[Lake Effect]

2021 RT 25 LE start battery fuse is blowing. The schematic notes this fuse goes to the AC to DC charger.
Any idea as to what the problem may be?

 

[venajeff]

My first step is to always begin with replacing the battery, unless it is new within 1 year. If that doesn't stop the charging line fuse from blowing, you will probably need to replace the charger.

 

[SKing]

Fuses aren't cheep so identifying what is causing it is helpful. When does it blow? Can you isolate things from the circuit to make it stable? (lift the wire going to the DC DC charger etc.)

 

[Submariner]

2021 RT 25 LE start battery fuse is blowing. The schematic notes this fuse goes to the AC to DC charger.
Any idea as to what the problem may be?

Trace the wires to ensure it actually goes to the AC to DC charger (battery charger).
It could also be the DC to DC charger fuse (engine to house).

The above two fuses are right next to each other on the bus bar.

I've heard of salt water (from a leaky raw water wash down connection) dripping down on the DC to DC charger, shorting it out electrically.

 

[Lake Effect]

Trace the wires to ensure it actually goes to the AC to DC charger (battery charger).
It could also be the DC to DC charger fuse (engine to house).

The above two fuses are right next to each other on the bus bar.

I've heard of salt water (from a leaky raw water wash down connection) dripping down on the DC to DC charger, shorting it out electrically.

I just attempted to trace the wire attached to the start battery fuse to determine where it goes. It travels behind the mounting board but the right size and color wire does connect to the DC DC charger. With the boat on shore power and battery charger connected, the start battery takes a 14v charge. When I touched this wire at the charger, I badly burned my fingers. Very hot connection. I switched the battery charger off. The start battery then tested 12.8v but will soon be dropping voltage.

There is a similar (same) size and color wire (red) wire traveling behind the mounting board attached to the AC charger mounted below the dc to dc charger.