Should I add extra fuse to SmartMPPT75/15

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cybermaus asked Sep 4, '20

Should I add extra fuse to SmartMPPT75/15

The SmartSolar MPPT 75/15 has a build in fuse. But what does it secure, and should I add an extra one.

Is it securing the Battery, or the Load. And does it make sense to add another one?

The load would go to my distribution panel (formerly connected to the hitch) and has a fuse of itself. Of course I would add a fuse as close to the battery itself as possible, but the MPPT is like 40cm away from it, lead wise.

I am assuming putting a fuse on the solar panels would not make sense. Yes, I can short them, but I would want it to be able to deliver its maximum capacity without blowing, and it seems silly to add a fuse for more Amps then the Solar can deliver.

MPPT Controllers fuses

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Answer 1 · 2020-09-04T21:41:45Z

Justin Cook answered · Sep 04, 2020 at 09:41 PM

Hi @cybermaus, the fuse in the Smart 75/15, as detailed in the user manual, exists only as a reverse battery polarity protection: it does not protect the battery positive circuit, nor the PV input, nor the load-out ports.

As such, yes, you absolutely must have a fuse or breaker as close to the battery as possible that protects the circuit from the controller to battery; you absolutely must have a fuse or breaker on the positive circuit of the load-out port (as close as possible to the controller) and you should have a fuse or breaker on the PV input to the controller, if for no other reason that you need to be able to isolate the controller from PV power if you need to, without either waiting until dark or climbing up and covering your panels.

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Answer 2 · 2020-09-05T05:44:17Z

cybermaus answered · Sep 05, 2020 at 05:44 AM

Ok., clear.

Good point about the PV fuse too, I had not considered that. More of a switch then a fuse, but we may as well have 3 identical wire boxes.

Thanks.

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