New house battery wiring and terminal fusing

[phantomracer]

Getting my ducks in a row to install my new firefly group 31 batteries...after killing my batteries

Installing 2 batteries in parallel. I believe the current wire in the boat is 2/0 unfused. Would like to fuse it properly. I am guessing 330A fuse? Any particular fuse/breaker better than others? Best practices installing them?

I don't plan on using the house bank to start the motor, but not ruling it out, as it is possible to do so, so it needs to be appropriately fused.

I am either having new terminals installed on the battery wires, or having them remade all together. Just want to ensure they are made correctly for the fuse I am going to use.

[phantomracer]

took too long to edit.. but was thinking of this. looks like a nice elegant solution. or is there a better fuse type to use?

MRBF Terminal Fuse Block with a 300a fuse on it. The new battery is a bit more than 2 inches shorter than the old batteries, so height shouldn't be a problem.



The battery has a 3/8 terminal. This mount to battery plate is apparently 3/8. It has a 5/16 stud for the battery cable.

If I go with this, should i have the battery cable terminal sized to 5/16, or go with 3/8 to be more flexible in the future, or does the 1/16 not really matter?

[smac999]

I've installed 100's of MRBF's . they are great. carry spare fuses


make the cable 5/16. it's makes a big diff when it's on the post

[Stu Jackson]

And you do know that these fuses are sized to protect the wires, right?

[phantomracer]

Originally Posted by Stu Jackson

And you do know that these fuses are sized to protect the wires, right?

yup

wanted to ensure the fuse sizing (300a) was appropriate for the 2/0 wire, and which fuse was a good choice and best practice

[nigel1]

I also used the Blue Seas MRBF's, very tidy solution.
Also used a double one on the terminal where the charging cable connects, with one fuse rated for the main battery cable, and a smaller rated fuse for the smaller charging cable.

[pcmm]

If you go with those, look around, Blueseas (in a lot of cases) just rebrands other stuff. that MBRF for example is actually made by "Cooper Bussman" and costs $8 for the block and another $7 for the fuse! and you can buy spare fuses too! I get alot of my stuff from waytekwire.com as it's half or better the price of blueseas from a chandlery! my 200amp windlass breaker cost $36 from there ( same part number as blueseas) where the blue seas version was over $100.... do the research and it will pay off

[Privilege]

It's always good to have large or oversized wire but do you need a 330amp fuse? Are there any circumstances in which you would be drawing anything close to that? My house bank has a 100amp fuse (but I don't start big engines with it). Even dropping your fuse down to 150amp would likely cover everything, but then of course, I don't know your boat and you might be running a large windlass from the bank or charging it at 200amps.
However, your two 100ah batteries will be providing 200ah capacity so I'm guessing that you wont be using them for very high loads.


Your fuse should always be placed as near to the batteries as possible and before any branches go off to distribution panels or anything like that.

[ohharry1]

I have just installed new batteries and wiring (and a few other bits and pieces). You really should shop around for all your hardware. For example 300 amp Class T fast acting fuses (inline with the inverter) are $57 at Waytekwire.com, $42 at Bluesea.com, and $33 at iboats.com. Of course sometimes the shipping, transit time, and taxes might even things out a bit but definitely worth spending the time. My total installation is around $4.5k and that is almost $1k cheaper than my initial costing...just by shopping around.

Don't tell my wife but with the money saved on this job I think I can almost fund the next project...

[Dave Lochner]

Originally Posted by pcmm

If you go with those, look around, Blueseas (in a lot of cases) just rebrands other stuff. that MBRF for example is actually made by "Cooper Bussman" and costs $8 for the block and another $7 for the fuse! and you can buy spare fuses too! I get alot of my stuff from waytekwire.com as it's half or better the price of blueseas from a chandlery! my 200amp windlass breaker cost $36 from there ( same part number as blueseas) where the blue seas version was over $100.... do the research and it will pay off

Thanks for the lead on Waytek. Wish I had known that last year when rewiring my boat.

FWIW, Cooper Bussman is a division of Eaton Industries and they still make stuff in the US. Cooper has a good sized factory about 2 miles from my house.

[Stu Jackson]

Originally Posted by phantomracer

yup

wanted to ensure the fuse sizing (300a) was appropriate for the 2/0 wire, and which fuse was a good choice and best practice

Go to the Blue Sea website, resources tab IIRC, there's a great PDF file on fuse and wire sizing. Bookmark it.

[Chuck Hawley]

I have a similar installation. I have three group 27 AGM batteries that are jammed into an under-berth location. I wanted to fuse them against mutual discharge (one cell in one battery failing and causing a meltdown), so I put a 100A Blue Seas Terminal Fuse at each positive terminal, then connected the three batteries together with a copper bar. It's very compact, low resistance, and I feel that the 100A fuse will prevent a China Syndrome.

While this bank is not normally used to crank the Yanmar, it has up to 300A in case I need to parallel it with the starting battery. I also run a Heart Freedom 15 inverter, and it has more than enough current capacity for that at full load.

So, my advice would be to use the smallest fuses you can manage without having nuisance "blows".

Chuck Hawley
Alerion Express 38 Yawl "Surprise"
Navigare necesse est.

[phantomracer]

Originally Posted by Stu Jackson

Go to the Blue Sea website, resources tab IIRC, there's a great PDF file on fuse and wire sizing. Bookmark it.

Thats where I got the 300a fuse from

I was just confirming that it is appropriate and I was reading the chart correctly.

[phantomracer]

Originally Posted by Privilege

It's always good to have large or oversized wire but do you need a 330amp fuse? Are there any circumstances in which you would be drawing anything close to that? My house bank has a 100amp fuse (but I don't start big engines with it). Even dropping your fuse down to 150amp would likely cover everything, but then of course, I don't know your boat and you might be running a large windlass from the bank or charging it at 200amps.
However, your two 100ah batteries will be providing 200ah capacity so I'm guessing that you wont be using them for very high loads.


Your fuse should always be placed as near to the batteries as possible and before any branches go off to distribution panels or anything like that.

I was going by what Blue Seas recommended for the wire size, about 330a, so round down to 300 should be fine. Was just trying to confirm that I read the chart correctly..and if that fuse type was any good.