I've got a simple solar charging setup on my 12V boat battery. It's controlled by a MPPT 75/10 which worked fine for 2 years. Recently battery was dead and the guy who does my electrical work said a fuse inside the MPPT had blown.
What could cause that? What investigation should I perform? Should I install a fuse elsewhere in the system to protect the MPPT's internal fuse?
Thanks.
Don't these units have a 5 year warranty? Contact your seller/installer.
It's impossible to say with certainty, but if you're too close to the 75V limit, you can pop the controller. Cold weather causes PV voltage to increase by 10% and more.
Concerning last question, all wires should have over-current protection (OCP). The controller wire to the battery should have a fuse/breaker protecting the wire. The PV wires to the MPPT only need a fuse/breaker if you have more than 3 in parallel, or are using very very thin wire. If using 3 or more, you need a fuse/breaker on each string of panels.
