Fuse or Circuit Breaker

mjohns2

Observer
I'm still debating whether or not I truly need a single or dual batteries. So I kind of want to start off with a single, with the option to move to dual batteries. My research has lead me to the Blue Sea products, but this has also raised additional questions. From the main battery, it's my understanding that, a fuse should be used between the battery and the fuse block. My question is does it have to be a fuse block, can a circuit breaker be used instead (what's "best practice")?

Battery -> Blue Sea Systems MEGA/AMG Safety Fuse Block -> Blue Sea Systems ST Blade ATO/ATC Fuse Blocks

vs

Battery -> Blue Sea Circuit Breaker Surface Mount 285 (120 amp) -> Blue Sea Systems ST Blade ATO/ATC Fuse Blocks
 
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DaveInDenver

Middle Income Semi-Redneck
Either a fuse or circuit breaker is fine. My feeling is fuses are simple and cheap. They're tolerant of worse environment and vibration. Breakers are usually smaller when you start going up in capacity and somewhat more predictable as far as where exactly they will open. Ultimately it's six of one, half dozen of the other really.
 

dwh

Tail-End Charlie
Breaker has an advantage in that it's a switch that can be easily turned off. Another advantage is not having to carry spare fuses.

Otherwise it's either/or. Both do the job.
 

v_man

Explorer
On my rock crawler I have my starter powered through my aux. fuse box. There's a CB between the aux. box and battery. A flick of the switch on the CB and the truck won't turn over, so it's like a poor man's kill switch. It's nice to be able to shut off power when you want to...
 
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rayra

Expedition Leader
Breaker has an advantage in that it's a switch that can be easily turned off. Another advantage is not having to carry spare fuses.

Otherwise it's either/or. Both do the job.

Another consideration is adding an aux fuse block that uses the same size/form-factor fuses as your vehicle, so you can carry common spares or rob from one fuse block to restore a function in the other.
 

rayra

Expedition Leader
I've got CBs everywhere. Like mentioned above, I like being able to cut power to a circuit by flipping a switch.


No reason you can't do both. Fused supply near the power source for hazards / danger, switch downrange of that in the interior for the device(s). Safer to do it that way anyway.
 

DaveInDenver

Middle Income Semi-Redneck
My thought is if you need a switch put one in and let the circuit interrupter do its job. For occasional use it's fine, that's why they have switchable breakers. But even the best MIL-PRF-66529 types are only rated to a fraction of the number of mechanical cycles (10,000 total, 6,000 powered) as a plain old Carling Contura switch (which are rated to 150,000 cycles minimum).
 

dwh

Tail-End Charlie
Another consideration is adding an aux fuse block that uses the same size/form-factor fuses as your vehicle, so you can carry common spares or rob from one fuse block to restore a function in the other.

OP was talking about a battery main line. ANL fuse. Not likely to find any of those elsewhere on the vehicle that can be borrowed in a pinch.
 

dwh

Tail-End Charlie
My thought is if you need a switch put one in and let the circuit interrupter do its job. For occasional use it's fine, that's why they have switchable breakers. But even the best MIL-PRF-66529 types are only rated to a fraction of the number of mechanical cycles (10,000 total, 6,000 powered) as a plain old Carling Contura switch (which are rated to 150,000 cycles minimum).

Switching the battery main line on/off is never going to happen 6000 times.
 

DaveInDenver

Middle Income Semi-Redneck
Switching the battery main line on/off is never going to happen 6000 times.
I know that, as a main disconnect that is exactly why breakers have a switch. You might do that twice, when you prep the truck to leave and when you return and park the rig. Over the life of the breaker it might be done a hundred times. Totally legitimate use and clear advantage over a fuse.

I was thinking of using one in place of a $5 CMB or CLB resettable breaker and a $10 panel switch that you might use every time you switch on lights or whatever. You might do that in the thousands of times in the life of your truck. Those cycle life numbers aren't guaranteed unless you're buying actual military components.

So a Contura while said to last 150,000 usually doesn't and the same is probably true of a Blue Sea breaker that is said to meet MIL-PRF-66529 probably won't have been lot tested to guarantee it actually meets it. Since it's primary duty is to protect a circuit I'd prefer to stay *well* within its life cycle expectancy.
 
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DaveInDenver

Middle Income Semi-Redneck
OP was talking about a battery main line. ANL fuse. Not likely to find any of those elsewhere on the vehicle that can be borrowed in a pinch.
It may be easier to carry an extra ANL with you than to have back up for a bad breaker. It's a mechanical thing, they do sometimes fail. It's usually possible to find large fuses at car stereo shops, electrical supply houses, marine suppliers, etc. Although that's also gonna be the case with common type breakers, too. Unlike what I've been using recently, those MRBF fuses. Those aren't very common anywhere outside of online but darned if they aren't convenient. But I just keep a few extra with me. If you blow a main fuse it's probably something serious like a cut winch cable or stuck starter so having one or maybe two spares is more than sufficient since you'll have to fix something major anyway.
 

rayra

Expedition Leader
OP was talking about a battery main line. ANL fuse. Not likely to find any of those elsewhere on the vehicle that can be borrowed in a pinch.

vman and sleepwolf talking about aux circuits, mon quibbling Statler.
 

dwh

Tail-End Charlie
vman and sleepwolf talking about aux circuits, mon quibbling Statler.

You quoted me, not them, and I was talking about the main line - in response to the OP's question.

Dunno anything about Statler except I think I've seen it in zimm's .sig. I'm guessing it's a TV related thing and you meant it as an insult. Didn't work.
 

dwh

Tail-End Charlie


No, not the same at all. One is just a fuseblock. The other is a fuseblock with integrated relays and remote switching of the relays.
 

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