Battery circuit breaker on negative terminal

The other serious issue with all of these fuses is their dead short AIC (amperage interrupt capacity) rating. Mega is maybe 2000 amps, ANL is 6000 amps, class T is maybe 20,000 amps. ANL is approved by ABYC for fusing large battery banks, BUT, if you use lithium batteries, or very large battery banks, they can put out more than 20,000 amps instantaneously, which would overwhelm ANL fuses, and potentially all fuses. AIC rating is the ability of the fuse to stop a dead short in amperage. If the fuse blows, you think the current simply stops, but that is a false assumption, if there is enough current behind the fuse, a fuse with a lower AIC rating cant stop the dead short of 20,000 amps produced by a lithium battery. The problem gets worse with higher voltages.

DC Circuit Protection - Blue Sea Systems

If your using Lithium batteries, or very larger battery banks, you should find out if your fuses are any good against shorts in the wiring. You may discover your fuses are like might as well have no fuses.
Energy Control - Sail Magazine

 

It will be hard to boot a sideways mrbf.

Most every guy on the forum understands the battery box strap holds the box down. I said you could use a longer strap if I wasn't clear enough for you.

Your entire setup is wrong afaic.

You really need to run one big fat wire to a T fuse and then to an mrbf bus.

I did have a hard time seeing the picture well as it seems too close, but I'd call it a hodge podge. Please don't be offended. I don't know the boat. A smaller boat is difficult to do real well on space limits.

If you have some space near the batteries, you ought to be running a power bus with mrbf fuses. Each wire has to be fused within 7" of the post otherwise and I see none.

 

Here is an incomplete version of something done better. The power comes into the switch from a t fuse. The switch is flipped and power is sent to the mrbf distribution bus.

This work is unfinished, so don't be super critical of it.

I am just explaining your wiring does not appear to be fused properly. The two wires in the distribution are both fused with mrbf to 2 gauge wires and one goes to the dc distribution and the other to a simple fuse block. All are opened for the pic.

 

Wont have to rubber boot a sideways mrbf. The box lid will cover the entire thing.
If the MRBF is under the lid that is good enough.
Not going that way with any of this, so there is no fusing of any starter wiring yet.
Boat was built in 1970, so I dont have to do anything regarding fuses.
I have seen a lot of older boats, and very few of them the owners tried to improve the main battery wiring.
I can understand new construction, being required to meet code, but old construction there is no forced upgrading required.
And think about this, I know the old starter wires, most of them are over 50 years old, and guess what, it has never shorted itself out, not in 50 years, with no fuses anywhere.
And every wire, I have had off and in my hands, and they are in fine shape.

 

One single 300 amp fuse on a short wire about 7 inches long is doable for the starter bank, and that single fuse will cover almost all the wires shown in my picture I linked to earlier. All I need now is to make a short connecting wire to run to the ANL fuse block which will be screwed to the plywood right behind the start battery. Now If I also put the same ANL fuse right behind the house GC15 golf cart batteries joined in series, every single wire on that side would also be fused by that single ANL fuse. You could have 20 large wires running off all over the place yet all would be fused as they all come together to a single junction point. I have 2 battery banks, so only 2 main fuses are needed. I already have the house fused at 140, inverter at 500, lectrasan at 100, but there is no main fuse for the house bank. The connecting wire runs about 15 inches from the rotary switch to the fuse block. But of course there is no fuse off the house bank batteries to the rotary switch. Not in 50 years of boat use has any one sabotaged the DC main wiring on this boat by leaving wire lug nuts loose, or allowing wires to rub against an engine to cause a failure.

 

Well, if you don't want to do it right, then you are on your own afaic.

 

Interesting that right for you means only MRBF terminal fuses right on the battery. There is no right or wrong, there is just better and worse, everything in life is that way. ANL fuse holders are not wrong, I do agree terminal fuses are better, but I refuse to use them, they dont fit my situation well, and the ANL fuse is good enough. Last 50 years boat had no need for fuses. Never in 50 years did a situation occur to cause a main wiring short, and that means likelihood of one occurring goes down every additional year that nothing happens. Kind like life expectancy, the longer you live, the more likely you are to live longer.

 

I've been following along here for days and keeping my mouth (keyboard) shut. I don't know what kind of boat we're taking about or any specifics about the battery banks or the electrical system of the boat you're working on. I can't offer any specific advice because I don't see enough information about the situation. The only comment I'll offer is that all circuit breakers or fuses are safety equipment designed to prevent fire. They're insurance. We spend a lot of money on this type of insurance and most of the time the breaker never trips and the fuse never cuts the current. That doesn't mean we shouldn't install these devices. The MRBF is arguably the best protection for a boats battery banks. I would find a way to make them work. Where there is a will there is a way.

As for life expectancy, the longer you live, the closer you are to your death. I'd add that as your electrical system ages your boat is far more susceptible to electrical shorts, bad grounds, open circuits and other system failures. Chafe can be a real problem on older boats causing shorts that can cause fires. As wire ages corrosion related to humidity will effect conductive capacity. This is especially true with non-tinned, non marine wire and cable. Heat cycling in wiring that is too light to carry it's loads will also cause accelerated insulation breakdown.

Good luck with your project and be careful out there.

MIA

 

The reason I am done supporting your effort is the idea you suggest NO FUSES is okay, but asked for help fusing. This dichotomy makes little sense.

Please do not suggest I implied only a certain type fuse was required.

This is a place where people come for help.

Wires are sized and fused accordingly. If you plan to redo things, why not right? If you have no intention of fusing large wires; then what is the point?

 

Check out Maine Sail's video, it is exactly what I thought. He fused a small 8 gauge wire to a 300 amp terminal fuse and created a DEAD short situation using a massive lithium battery bank. The fuse blew and the 8 gauge wire did not even get warm. He makes mention that your better with a fuse than none at all, even if hugely over fused for the wire, and mentions we are protecting the wire against shorts. So my Gauge 2 wire I added running 15 feet to start my Onan generator will be well protected with the 300 amp ANL fuse against a dead short.

(16) Marine Rated Battery Fuse Trip - YouTube

 

I never said I was not going to use the ANL fuse I ordered, just that I dont have to fuse the starter bank at all. I am doing more than others did for decades on every boat I have ever seen or read about...starters were not fused. Look at the video, a 300 amp fuse instantly blows on an 8 gauge wire with the 8 gauge wire left in perfect shape, as I thought it would. He even says in the video people told him the wire would melt due to the current. But no they dont. Think about it, at 8 gauge, the wire is still bigger than the fuse link itself inside the fuse. And we are protecting against wire shorts which are what causes fires, not short cranking events where the starter spins a few seconds.
(16) Marine Rated Battery Fuse Trip - YouTube

 

Anyone who tells you the starting wires must be breaker or fuse protected is in ERROR.
Several people in this thread have said that to me, they should be ignored, they are bullies

It is optional to put in a fuse which I already knew, and honestly it can cause a problem, say your start battery is low and lugs the engine over, the current flow goes up higher than normal then and very well could blow a fuse leaving you unable to start the motor in a hazardous situation, whereas otherwise it could have started.

I am discussing adding a breaker or fuse to the start battery bank and got all sorts of crap responses...
From the Blue Sea site,

"Notice that wires intended to carry engine-starting currents between the batteries, the switch, and the starter, are not required to have main-circuit-protection devices installed.

This exception is based on the notion that the starting battery would have just enough power to handle starting the engine, and the wiring would be appropriately sized such that the full capacity of the battery would be unlikely to overstress the wire. It was also assumed that the batteries would be very close to the engine.

Some modern installations violate some or all of these assumptions with very large house banks that may include an emergency cross connection switch, making them part of the starting system. The house banks may be some distance away from the engine in different compartments. Some experts believe that all circuits on a boat should be protected - including the start circuits. However, at this time, this is not an ABYC recommendation."

 

U r 1 funny duck. I also never suggested fusing the start circuit, in fact, I excepted it.

Please refrain from suggesting I said things I did not.

The reason for fuses is to protect wires. Largely from catching fire.

 

Well, you said this for example in post #24

"The reason I am done supporting your effort is the idea you suggest NO FUSES is okay, but asked for help fusing. This dichotomy makes little sense.

Please do not suggest I implied only a certain type fuse was required."

This thread was started by me referring to fusing the start battery bank, which does not have to be fused. I mean your own words testify contrary to what you say now.
NO FUSES is ok. But I have decided to use an ANL fuse. That is the whole point of a discussion, to figure things out, and what to do, think about making a choice.
Everybody can see this who has followed this thread.
And I thought you were 'done with me', so why are you coming back with stuff like this? You don't recognize your own inconsistency, you're acting like a bully.

 

I have an extensive track record supporting people. The reason I keep returning is your continued false allegations.

first, that I said only mrbf

then you infer I said to fuse the start wires

now that I'm a bully

the moderator ought to step in now