Hey guys, have most of my solar set up ready to install, just have one last thing I still cant fully grasp (I am pretty green to this electrical stuff). I have a 40amp mppt charge controller that will be running to a single 12v 155ah battery from renogy. I am running the provided 10awg able to connect the charge controller to the battery. Will a 30amp fuse be sufficient to protect the charge controller? Bigger? I am still a bit confused as to what size fuse I would need. I only have a single 100watt panel as its all I could afford at the moment, but planned to be able to add additional panels.
Fuse confusion
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Optimistic Paranoid
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The general rule of thumb is that you fuse to protect the wire and prevent fires. 10 Gauge wire should have a maximum fuse size of 30 amps. If, for some reason, more than 30 amps were to flow through 10 gauge wire, it would dangerously overheat and probably cause a fire.
Now, the exception to the rule of thumb is if the charge controller's manual specifically called for a smaller fuse than 30 amps in order to protect the controller itself from too much current that would burn it out. In the absence of any such specification, stick with the 30 amp.
Now, the exception to the rule of thumb is if the charge controller's manual specifically called for a smaller fuse than 30 amps in order to protect the controller itself from too much current that would burn it out. In the absence of any such specification, stick with the 30 amp.
Wabbit
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Currently, I don't have a fuse between my CC and battery. How important is this fuse? Will look into it myself, but any real world experience/knowledge is appreciated. Thanks!
EDIT: From what I read, yes it should be fused. I don't remember seeing it on diagrams when I was setting mine up, but the diagram at the following link does show one should be there.
https://www.windynation.com/jzv/inf/how-properly-fuse-solar-pv-system
EDIT: From what I read, yes it should be fused. I don't remember seeing it on diagrams when I was setting mine up, but the diagram at the following link does show one should be there.
https://www.windynation.com/jzv/inf/how-properly-fuse-solar-pv-system
Any wire connected to battery positive should be fused. The maximum amp for 10 agw 105C rated wire is 60 amps outside an engine room. The problem of 10 agw used for charging is the voltage drop reducing the charge getting to the battery. One needs to know the distance between the CC and battery to determine that. But at 10 feet, 10 awg, 40 amps, you would have the maximum recommended voltage drop of 3%. As for the fuse, less than or equal to recommended safe current, 60 amps, but more than rated CC 40 amps. With 10 awg, I would fuse 60 amps as close to the battery as possible. The larger fuses have less voltage drop than smaller. The voltage drop in the charging circuit should be as small as we can make it, so more charge gets to the battery. You may need larger cable.
Spaceman Spiff
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1X on what OP said.
A fuse between the solar panels and charge controller also gives you an easy way to disconnect the panels when doing maintenance on your system.
And use the largest fuse your wiring can handle (to minimize voltage drop), unless your CC specifies a lower value fuse.
You should also have a fuse between your batteries and everything else (in your case 30 amp also).
-- Spiff
A fuse between the solar panels and charge controller also gives you an easy way to disconnect the panels when doing maintenance on your system.
And use the largest fuse your wiring can handle (to minimize voltage drop), unless your CC specifies a lower value fuse.
You should also have a fuse between your batteries and everything else (in your case 30 amp also).
-- Spiff
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