Oversized Solar Controller w/ Smaller Fuse & Wires

[windnsalsa]

Hi, I bought a used Epever 60a solar charge controller at an exceptionally low price. Its manual indicate an 80a fuse. But, I currently have only 2x100w panels. Maybe 300w-320w total next year.

Can I install a 20-30a instead of 80a fuse on the battery post for the battery-SCC connection? Then, I would be able to use a thinner wire [12awg-10awg]?  Good idea? Any negative?

 

[PlethoraOfGuns]

I would fuse both the wires going to the panel, and wires going to the battery. The size of the fuse is directly proportional to the wire size, as the wire is what the fuse is designed to protect. Even 320w won't make more than 30a, so I don't see a problem using 10ga and 30a fuse. But if you add more panels...

 

[windnsalsa]

I would fuse both the wires going to the panel, and wires going to the battery. The size of the fuse is directly proportional to the wire size, as the wire is what the fuse is designed to protect. Even 320w won't make more than 30a, so I don't see a problem using 10ga and 30a fuse. But if you add more panels...

Various vendors don't have a recommendation to fuse between panels and SCC when there are 2 panels, especially 2x100 as long as the wire is appropriate. But, does recommend with 3+ panels.

Yea, I am hoping that there are no negative aspects to use smaller fuse and wires, vs the manufacturers' recommendations.

 

[grandpa pete]

I would fuse both the wires going to the panel, and wires going to the battery. The size of the fuse is directly proportional to the wire size, as the wire is what the fuse is designed to protect. Even 320w won't make more than 30a, so I don't see a problem using 10ga and 30a fuse. But if you add more panels...

spend a couple of bucks more and put circut breakers..you don;t want to be looking for fusses out in Quartsite.....the circut breakers can be used as shutoffs when working on or adding to your system

 

[barleyguy]

Various vendors don't have a recommendation to fuse between panels and SCC when there are 2 panels, especially 2x100 as long as the wire is appropriate. But, does recommend with 3+ panels.

Yea, I am hoping that there are no negative aspects to use smaller fuse and wires, vs the manufacturers' recommendations.

It shouldn't be a problem. A smaller fuse is safer than a larger fuse. The worst problem would be that your fuses constantly blow, in which case you'll learn that you need a larger fuse.

 

[PlethoraOfGuns]

Well just remember that the fuse/circuit breaker is protecting the wire from a number of things. Yes, obviously overload protection, but don't forget about shorts. Wires running through the vehicle could always rub on some metal and then bad things happen.

 

[windnsalsa]

spend a couple of bucks more and put circut breakers..you don;t want to be looking for fusses out in Quartsite.....the circut breakers can be used as shutoffs when working on or adding to your system

My Dual Studs MRBF Terminal Fuse Block just arrived that connects directly to battery positive post: 1 stud for battery-SCC connection and other stud for battery-inverter [future purchase] connection. After confirmation from this thread, I'll be returning my 80a and exchange for a 30a fuse, which will allow smaller wires [already own] to be used. 

I read from this and other forums that breakers are not as reliable as fuses: trip at significantly lower amps than specification. Also, for the panels-SCC connection, I can disconnect mc4 connection at the SCC end. For the SCC-battery connection, I have a switch.

 

[windnsalsa]

Well just remember that the fuse/circuit breaker is protecting the wire from a number of things. Yes, obviously overload protection, but don't forget about shorts. Wires running through the vehicle could always rub on some metal and then bad things happen.

Please clarify, so you do or not agree that I can use smaller fuse & thus wires for my over-spec'ed SCC?

 

[PlethoraOfGuns]

As long as you don't add more panels that exceed the amperage rating of your wiring, you are good. Yes, you are safe to run 10ga with 30a fuse on a 60amp MPPT controller. If you do add more panels and you start blowing fuses due to overloading and you put larger fuse in without upgrading wires, you risk burning everything to the ground.