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Old 01-23-2018, 06:03 PM   #1
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2013 25' Flying Cloud
Middleton , Idaho
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50 or 60 amp MRBF fuse?

I want to put a Blue Seas MRBF fuse on the factory 6 ga positive battery cable at the battery. I looked up several charts and most say to use a 60 amp fuse with 6 ga battery cables (some say 80 to 100 amp). But I have seen some past postings where 50 amp fuses were recommended for stock Airstream battery cables (which I assume are 6 ga).

Any recommendations from those who have done it?

Thanks- Bob
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Old 01-23-2018, 06:33 PM   #2
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The fuse is intended to protect the wire. So if references say to use 60 amp, that is the most you should use. No problem using 50 amps, as long as the wire will not need to carry more.

Does it feed an inverter? What is the capacity of your converter? If either are more than 50 amps, go with 60.

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Old 01-25-2018, 07:15 AM   #3
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Thanks Al, that makes sense. There is only a small 300 watt inverter, but the converter is rated for 55 amps. I'll go with the 60 amp fuse.
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Old 01-25-2018, 11:25 AM   #4
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The temperature rating of the cable insulation will determine the safe amperage capacity. 6AWG marine cable has 105C temperature rating. Other wire can be as low as 75C. Also if installed in hot areas or in bundles make a difference. The lowest rated 6 AWG, in free air, is 75 amps. Another thing to worry, will 6 AWG have too high a voltage drop for your inverter or charging circuit? That is dependent on the length.
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Old 01-28-2018, 10:19 AM   #5
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Thanks Zil, that explains why I saw the higher amp rating on the Blue Sea site-- they were referring to a higher temp rated wire.
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