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MEXICOWANDERER

las peñas, michoacan, mexico

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Posted: 01/03/18 07:37pm Link  |  Quote  |  Print  |  Notify Moderator

Yes that is correct. This of course is a vital protection when cable is passed beneath floorboards. As a plus, if you ever need to expose or work on the connector in the bed, the breakers can be manually clicked off.

And a tip, the electrical studs on the breakers is 1/4". Extremely heavy cable needs to have strain relief support a few inches away from the studs. Clamp down the wires tight then flex them by hand to achieve near zero pull force on the studs. I use bronze or stainless flat washers on top of the terminal to achieve better fit.

MEXICOWANDERER

las peñas, michoacan, mexico

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Posted: 01/04/18 01:51pm Link  |  Quote  |  Print  |  Notify Moderator

[image]

https://www.delcity.net/store/Aluminum-Clamps/p_800834.h_66350

S Davis

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Posted: 01/04/18 09:59pm Link  |  Quote  |  Print  |  Notify Moderator

Thanks, I got two more Bussmann 120amp breakers on the way. Should I have fuses at each battery as well?

MEXICOWANDERER

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Posted: 01/05/18 06:03am Link  |  Quote  |  Print  |  Notify Moderator

Any time there exists a possibility of over amping the wire conductor or damaging the generating supply voltage, fuses should be used. Inside the Megawatt and Meanwell power supplies for instance there are circuit board 10-amp AC fuses.

When an alternator shorts to ground, voltage at the field decreases so rapidly, the alternator cannot over-amp itself to death. This can be shown on a test bench where over-loading the alternator will quickly bring amperage potential down from say 130 amps to 20. A seven gauge power wire would therefore be intrinsically protected against over amperage. When power to the rotor field is slumped output is slumped. Therefore protection for this line is because the battery can cause wire overamperage not the alternator.

S Davis

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Posted: 01/05/18 02:10pm Link  |  Quote  |  Print  |  Notify Moderator

So it sounds like it would be a good idea to come off the batteries and through a fuse and then a battery switch and then to the buss bar, what should I fuse the batteries to?

brulaz

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Posted: 01/06/18 05:46am Link  |  Quote  |  Print  |  Notify Moderator

S Davis wrote:

So it sounds like it would be a good idea to come off the batteries and through a fuse and then a battery switch and then to the buss bar, what should I fuse the batteries to?


Usually you fuse to protect your wire, so the fuse depends upon wire size (and location).

Blue Sea has some good charts:
http://assets.bluesea.com/files/resources/reference/20010.pdf

I would use the smaller size fuse for engine room/bundled wires.


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Posted: 01/06/18 08:20am Link  |  Quote  |  Print  |  Notify Moderator

I thought you were using a breaker at each end as your "fuses". You asked if you also needed fuses. Mex did not answer that. I do not know the answer. I get confused over "slow" vs "fast" acting and when to use which.


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S Davis

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Posted: 01/06/18 12:12pm Link  |  Quote  |  Print  |  Notify Moderator

Ok so going by that chart using 3/0 wire from each battery it looks like a 400amp fuse to protect the battery wires and main buss bar.

MEXICOWANDERER

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Posted: 01/06/18 01:39pm Link  |  Quote  |  Print  |  Notify Moderator

FUSES are EXACT and almost instantaneous. They are also a pain-in-the-ass to have to change. Fuses are wonderful to protect sensitive electronics, the inverter, converter, stereos, computers etc.

Circuit breakers are sloppy. Not exact. React instantly only when badly overloaded, are forgiving and heal themselves quickly and automatically.

BREAKERS are perfect to protect main line trunk power cables. FUSES will blow if a power source is hooked up backward. But small appliances will still burn out with reversed polarity.

The actual only NEGATIVE with using 400-amp T class fuses on main battery cables is you'd better carry spare(s), and the fusing block should be in a very easy to get to place. If a fuse fails what do you do? Try another fus...****! ?

That's why I prefer breakers. Class T fuses are not cheap and an inadvertent "OH NO!" does not become an exercise of feeding more fuses by trail and error until the problem is found.

There is nothing wrong with using a ultimate limit fuse ahead of a circuit breaker. An example by toad has a 30-amp fuse, then a 20 amp breaker protecting the radiator fan motor. When the fan motor shorted, it blew the fuse -- telling me the 20-amp breaker reacted slowly. Then the circuit went "open circuit". Diagnostics were a snap. The motor is now open circuit but before that it had shorted. No sense in troubleshooting further. Motor bad. Bad motor. Recycle motor.

S Davis

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Posted: 01/06/18 05:20pm Link  |  Quote  |  Print  |  Notify Moderator

MEXICOWANDERER wrote:

FUSES are EXACT and almost instantaneous. They are also a pain-in-the-ass to have to change. Fuses are wonderful to protect sensitive electronics, the inverter, converter, stereos, computers etc.

Circuit breakers are sloppy. Not exact. React instantly only when badly overloaded, are forgiving and heal themselves quickly and automatically.

BREAKERS are perfect to protect main line trunk power cables. FUSES will blow if a power source is hooked up backward. But small appliances will still burn out with reversed polarity.

The actual only NEGATIVE with using 400-amp T class fuses on main battery cables is you'd better carry spare(s), and the fusing block should be in a very easy to get to place. If a fuse fails what do you do? Try another fus...****! ?

That's why I prefer breakers. Class T fuses are not cheap and an inadvertent "OH NO!" does not become an exercise of feeding more fuses by trail and error until the problem is found.

There is nothing wrong with using a ultimate limit fuse ahead of a circuit breaker. An example by toad has a 30-amp fuse, then a 20 amp breaker protecting the radiator fan motor. When the fan motor shorted, it blew the fuse -- telling me the 20-amp breaker reacted slowly. Then the circuit went "open circuit". Diagnostics were a snap. The motor is now open circuit but before that it had shorted. No sense in troubleshooting further. Motor bad. Bad motor. Recycle motor.


Ok thanks, so what size breakers should I get for each battery?

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