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Author Topic: Ignorant question about putting a 30A Fuse from controller to batteries  (Read 235 times)

BigSkyTrailerGuy

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I just pulled the pin of a couple of 100W Solar panels and a Renogy Wanderer controller. 

They specify a 30A fuse between the controller and the batteries --  But if that cable is 4 AWG (for minimum voltage loss),
doesn't the resistance of an in-line fuse negate our coveted current flow?

Sorry again for the ignorance.

John From Detroit

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Re: Ignorant question about putting a 30A Fuse from controller to batteries
« Reply #1 on: September 03, 2017, 07:06:03 AM »
No the fuse is a very short section of small wire. The 4AWG is 100's times longer

The resistance is "per foot" so being as the fuse is like 1" there's not much resistance there.
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QZ

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Re: Ignorant question about putting a 30A Fuse from controller to batteries
« Reply #2 on: September 03, 2017, 07:31:15 AM »
At 200 watts you will get 12 amps or less. If you push close to 30 amps through the fuse you may see insignificant heating of it. I have experienced it with anl fuses. Gadgets like https://www.amazon.com/dp/B01H3DKGFK?th=1 are a cheap way to protect and give you an easy way to disconnect. The high quality version is this https://www.amazon.com/dp/B004XXOVP0/ref=twister_B01ENZVS7G?_encoding=UTF8&psc=1. You may also want a disconnect between the panels and the controller  because some companies specify disconnecting the panels before disconnecting the battery. Your controller manual may mention it.

Gary RV_Wizard

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Re: Ignorant question about putting a 30A Fuse from controller to batteries
« Reply #3 on: September 03, 2017, 09:40:44 AM »
As QZ & John say, your max current flow is nowhere near 30A, so the fuse is insignificant in the circuit resistance. 4 AWG cable is probably way overkill anyway. Even 10 gauge will handle 200 watts (about 12A @ 16v) with insignificant loss, and 10 gauge is rated for 30A loads.
Gary
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Lou Schneider

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Re: Ignorant question about putting a 30A Fuse from controller to batteries
« Reply #4 on: September 03, 2017, 04:15:51 PM »
How far from the batteries is the solar controller?  Put it close by and the need for overly large wire becomes insignificant.

In any case, you do want a fuse close to the batteries in case you get an internal short in the controller or an external short in the wiring.  Better a fuse gets hot and blows than the wiring gets hot and starts a fire.

sunfighter

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Re: Ignorant question about putting a 30A Fuse from controller to batteries
« Reply #5 on: September 04, 2017, 08:10:57 AM »
Here's my 30 amp fuse setup. Being an old guy, I used the jumbo size fuse. (easier to see)  :D :D
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AStravelers

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Re: Ignorant question about putting a 30A Fuse from controller to batteries
« Reply #6 on: September 07, 2017, 11:26:18 AM »
I would install a Blue Sea 30amp circuit breaker disconnect switch like this: https://www.amazon.com/dp/B0055MV7AA/ref=twister_B01ENZVS7G?_encoding=UTF8&psc=1

This give you the ability to disconnect the controller much easier than pulling the fuse.
Al & Sharon
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2009 Chevy Colorado 4X4

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