12v electrical system help

[matt.beiter11]

I am currently planning my 12V electrical system using a 100ah battery to a blue sea 12 circuit fuse panel running only 6-7 of those to LED lights and a 90 quart fridge/freezer. Can anyone provide insight as to what size fuse or resettable circuit to place between the battery and fuse panel? I also plan on putting in 30 amp shore power and a solar controller for future panel installation. Attached is my crude attempt at a wiring diagram. Any advise and guidance is appreciated.

 

[carbon60]

The breaker/fuse at the battery is to protect the wire it is on. So factor how large of a wire that is, to get your correct fuse rating. I would avoid a breaker as they encourage one to just reset it and stick one's head in the sand, when there is a problem.

 

[dreadlocks]

Look at the bluesea battery post fuses, size it appropriately to your main fuse box feed so it'd pop before the wire melts.. I have like a 200A on mine with a heavy feed wire (00) coming off battery to distribution system.. wire can handle like 500A but my battery cant output more than 200A and it can only do that for 30s max.

 

[vtsoundman]

Try again with that photo and label/list your loads rather than expect someone to decode your circuit....you'll get better fidelity (answers).

An MBRP fuse is just about the best fuse you can use for a battery feed. Skip the breaker unless you really need to disconnect the battery frequently.

 

[vtsoundman]

Look at the bluesea battery post fuses, size it appropriately to your main fuse box feed so it'd pop before the wire melts.. I have like a 200A on mine with a heavy feed wire (00) coming off battery to distribution system.. wire can handle like 500A but my battery cant output more than 200A and it can only do that for 30s max.

Is that 200A hardware limited by something like a series BMS? All batteries can produce tremendous short circuit current.

Also, that 200A fuse isn't going to protect your 200A limited source. Fuses follow an i2t curve and which basically means little current, long trip times or lotta current, short trip times.

 

[dreadlocks]

its not that it cant its that it shouldn't because thats the max rating for the battery. which I never normally approach, even with my 1200VA inverter.. its to pop if it exceeds 200A, because the only circumstances tha'd happen is there is a short.. its high enough over my maximum loads it wont nuisance trip, and low enough that none of the wiring or LVD's (225A) or anything down stream would be damaged from a short (including the battery)

 

[carbon60]

Depending on your physical layout, often that fuse/circuitbreaker is not really needed. You can save a couple dollars and eliminate at least two wire terminations
If your BlueSeas is basically adjacent to the battery and its conductor routed where its unlikely to be damaged, Its quite safe to eliminate if desired. Otherwise as mentioned prior, Its capacity is normally based on conductor size.

I disagree. But I'm shy from watching a friend's truck burn 400KM from civilization.

 

[matt.beiter11]

Thank you all for the comments. VTsoundman I am working on getting all my loads to establish current draw. I am quite the novice with 12v electrical so I am trying to learn as much as possible.

 

[vtsoundman]

No worries. start with a better photo of your schematic and list the loads. there is enough wisdom here for some decent SWAG amounts that someone will propose a value.

 

[Alloy]

A simple method to protect the wire is to bolt a BlueSea Mega or AMI fuse directally to the battery terminal then bolt the wire lug to the fuse.

Looking at your layout I'd go with 40 Amps (8ga) to the distance panel....but you may want to go up a little in case more battery capacity is added later on.

A battery disconnect is a good idea.


I like BlueSea 5031 dist. panels.

 

[matt.beiter11]

I have come up with a max load around 23 amps with the fridge 5amps, 5 lights 2amps total, battery monitor .2amp, water pump 7.5amps, and 8amps for a 4 port USB charger. The switch panel will have illuminated switches but I can't find a load value for it. Constant load will only be the fridge with intermittent use of the lights, USB charge ports and pump.

Alloy thank you for the recommendations. I was considering a battery disconnect switch but with the fridge as a constant load the only use would be while parked at home between trips.

 

[DaveInDenver]

I disagree. But I'm shy from watching a friend's truck burn 400KM from civilization.

That's why he said "depending on physical layout". If the fuse panel is located right next to the battery could likely be no real increase in protection by squeezing in a fuse to protect a very short length of wire that is unlikely to be cut anyway. But you may introduce more crimps and terminals and complexity of routing.

 

[carbon60]

That's why he said "depending on physical layout". If the fuse panel is located right next to the battery could likely be no real increase in protection by squeezing in a fuse to protect a very short length of wire that is unlikely to be cut anyway.

Right, I see that point now. I still feel like the panel itself should be protected, but it’s probably fine.

I have a length of 6ga run from the battery to the panel which is in he rear of my truck. 30A fuse at the battery.

A.

 

[javajoe79]

Personally I would size the wire and fuse to match the total rated output of your fuse block. That way any future upgrades or added circuits can just be added to the blue sea fuse block.

 

[e60ral]

Personally I would size the wire and fuse to match the total rated output of your fuse block. That way any future upgrades or added circuits can just be added to the blue sea fuse block.

that only works if the total rated output of the fuse block is lower than the wire rating