Fuse or Circuit Breaker

dwh

Tail-End Charlie
What thing paired with the Bluesea?

A relay module hiding down there under the wiring? Hard to tell in that pic.

But if so then yea, same net effect - fuses and relays. Just one has both integrated into a single unit.
 

JPaul

Observer
Personally I am going with a 200A MRBF fuse to my 3/0 power feed to my rear Blue Sea Safetyhub 150 fuseblock. I thought about a breaker but the fuse has greater amp blocking when it fails open (10,000 amps) than their 200A breaker does (5,000) which to my understand will become important when I increase the battery capacity in my system. Plus a fuse is dead reliable in the majority of cases, and I think especially so when used in a rough terrain vehicle.

Is it all overkill? Probably, but I'm building this thing to last a really long time so I am trying really hard to not cut corners and make sure that whatever I put in will only need to be done once. Plus a quality fuse and it's holder are less than a quality breaker, even if I pick up a couple spares. And like someone else mentioned, if my main fuse blows then there is something major wrong. Lastly, this is an auxiliary system so the fuse blowing will be more of an inconvenience than something that will stop me dead in the water.

Ultimately a breaker vs a fuse is up to you and your application. A lower amp system and/or a lower surge amp source can easily be accommodated by a breaker. Once you start going to a high surge amp source you'll want to reconsider to make sure that whatever is interrupting the current flow in case of a short will be able to keep the circuit open. If the in-rush of current is too great it can cause the circuit to remain effectively closed due to arcing and welding of the contacts in the case of a breaker (at least the welding is a scenario I can picture, I'm not 100% sure).

Take everything I say with a grain of salt though, I am by no means an expert, I'm just regurgitating the information I have discovered as I researched all this myself from credible resources such as Blue Sea and my own knowledge of electrical principles and theories I have accumulated over the years.

Sent from my SM-N950U using Tapatalk
 

Skeptic

Adventurer
I'm bringing a power line into the cab of my 4Runner that I can break out into individual circuits for an amateur radio and some other accessories. I was considering a circuit breaker between the battery and the penetration of the firewall, but when I started looking at the specs on your typical automotive circuit breakers, I'm finding maximum operating temperatures in the 150 to 185 F range. Even the Blue Sea Systems 285-Series breakers max out at 185 F. Do breakers fail beyond those temps? Don't know, but I'm sure under hoods temps can get past that point, particularly in summer.

Theoretically, fuses and breakers do the same thing, but one uses a thermal breakdown of a fusable link while the other relies on a mechanical operation that may not work so well at under-hood temps in excess of their stated limits. I realize that many manufacturers use breakers in their under-hood fuse/breaker assemblies, and I'm sure I can find a breaker built to some mil-spec that will operate reliably, but I think that a fuse is probably the simplest and most reliable solution for me.
 

DaveInDenver

Middle Income Semi-Redneck
You're supposed to derate fuses for temperature, generally about 0.5% per degree C. But even just at +20C over ambient (easily achievable in an engine bay) a fuse will hold about 10% less current than it's 25C/77F nominal rating.
 

JPaul

Observer
The automotive/marine breakers are generally thermally tripped, so heat will affect the amperage it will actually trip at, similar to the fuses derating, though I'm not sure what the curve is and Blue Sea at least didn't provide one for theirs.

I don't think they'll just stop working in high heat, but they will trip at lower amperage since it will take fewer amps to heat the bimetal switch enough to trip, and the operating temperature is probably part of that problem, after passing the maximum it will no longer be within an acceptable threshold, in addition to entering the point of possible structural failure of the device. When you get to the lower end it will take too many amps to heat the bimetal switch inside which can cause all kinds of other issues. But that's probably not really much of a concern in our applications.

Sent from my SM-N950U using Tapatalk
 

mjohns2

Observer
Thank you guys/gals so much. I think I have what I needed. I will post, once I get home from work, one more question. It’s really a quick diagram I’m going to follow. I want to make sure I’m doing everything correctly.


Edit: I apologize for the crude diagram. This is how I'm thinking of wiring everything. Does it look correct?

setup.PNG


MJ
 
Last edited:

mjohns2

Observer
First thank you guys guys/gals for you helpful input. I almost forgot to come back and report how everything went. Well, I completed the install and wiring this past Sunday (May 13, 2018) and it went completely smooth with one small hiccup (another story and another day).

Images can be seen here


Again thank you all very much for your patience and help.

MJ
 

mjohns2

Observer
Thank you guys/gals so much. I think I have what I needed. I will post, once I get home from work, one more question. It’s really a quick diagram I’m going to follow. I want to make sure I’m doing everything correctly.


Edit: I apologize for the crude diagram. This is how I'm thinking of wiring everything. Does it look correct?

View attachment 442527


MJ

I’ve noticed my frig turns itself off after shorter trips since the battery can’t get a good full charge.

I want to add a solar panel, and it’s required equipment, but how do I connect it based on the diagram above?

MJ
 

mjohns2

Observer
Two easy places to connect.
The 'pos & 'neg battery output of the solar controller, directly connect to the battery, or positive anywhere along the positive conductor between battery and Bluesea.(Of course with appropriate overcurrent device on solar controller positive lead)
Or, If you have a fuse space available on your Bluesea fuseblock, You can connect your solar controller battery positive output to that, and use appropriate size fuse. All negative connections can be made anywhere its handy.


Ohhhh man, no wonder there are no writeup on this. So I can just go straight to my Bluesea fuseblock since I do have space available and I ran an extra cable.

Would 10 Gauge Ga cable be okay from the solar charger to the battery?

I'm still doing my homework on this, but if I were to go with the AllPowers 20A Solar Charger Controller, is it safe to say that my fuse should be 20A?

And with a 20A fuse, is there a maximum size solar panel watt or volts I could use?


 
Last edited:

luthj

Engineer In Residence
First confirm you don't have excessive voltage drop in your fridge wiring. Confirm your battery is charged or not via open circuit voltage. Then asses your alternator charging voltage. There could be a large drop in the charging wiring.

What is your fridges cut-out votlage? 11V? 12.2V?

Then pick a solar controller that will actually charge your batteries properly. For flooded lead acid that is often 14.6V or higher absorb charge.
 
Last edited:

mjohns2

Observer
One thing about connecting solar to your Bluesea fusebox. If 100A circuitbreaker is switched off, The solar will keep the Bluesea fusebox energised as long as its exposed to sunlight.
Aside from possibly confusing, I cant forsee that being a major problem.
Just pull out the solar fuse along with switching off 100A breaker if you need to fully de-energise your fusepanel for some reason.


Excellent point and I don't think there's an easy way around that.



First confirm you don't have excessive voltage drop in your fridge wiring. Confirm your battery is charged or not via open circuit voltage. Then asses your alternator charging voltage. There could be a large drop in the charging wiring.

What is your fridges cut-out votlage? 11V? 12.2V?

Then pick a solar controller that will actually charge your batteries properly. For flooded lead acid that is often 14.6V or higher absorb charge.

It's an ARB 50qt fridge, I have it set to Switch off voltage to high which from my understanding is 11.8V.


The issue im having is, when I have a short drive, hot day, and no covered parking, the fridge works the battery. And within 5 hours I think it cuts itself off from the battery. When I come out for lunch the fridge is already in the high 50s. I'm hoping solar can help the battery some.
 

luthj

Engineer In Residence
Okay, so is your battery reading 11.8V after the fridge has cut-out? Even moderate resistance, or improper gauge selection can result in over 0.5V drop from the batteries to the fridge. If you battery is still showing in the mid to upper 12V range after your fridge has cut out, you may have a voltage drop causing erroneous safety cut-out.

The easiest thing to do is to turn the fridge on. Use a volt meter to probe the wires as close to the fridge as possible. Record the voltage, then do the same right at the battery terminals. Ideally you want less than 1% drop of about 0.125V. 0.3V would be my upper limit for a fridge with voltage cut-out feature.

I don't know what logic ARB uses on their voltage cut-out. It may be that it will restart once it sees a voltage above 11.8V (no load voltage). Some fridges will try a couple of times, but if the running voltage drops below the threshold it will lock out until the main bus rises above a higher setpoint (12.5V or so?)

Anyways, solar is still a great idea, just make sure you got all your bases covered.
 

dwh

Tail-End Charlie
It's a spiral-wound AGM. Set the Victron to bulk/absorb at 14.7v./14.7v (yes, both the same) and float at 13.8v.

No EQ.

Don't worry about the higher float voltage - that'll stop when the sun goes down anyway.
 

Forum statistics

Threads
185,534
Messages
2,875,615
Members
224,922
Latest member
Randy Towles
Top