MRBF or Class T Fuse Holder for Eve Double-Bolt Terminals?

[packrat1969]

Hello,

I'm in the process of building my second 12V LiFePo4 battery. This time around I'm using Eve 304Ah cells with the double-bolt-style terminal (correct me if there is a proper name for it). These terminals use (2) 6mm bolts instead of having a single stud like my last battery build.


I'm looking for some kind of low-profile fuse holder that will bolt directly to the cell terminal, using both 6mm fasteners. I would prefer to use a Class T fuse, but if that is not available, what about an MRBF fuse and fuse holder? My plan is that the fuse holder will be the last stop for the (2) 4ga wires before the battery's bulkhead +12v terminal. Once installed, all wiring will be fastened in place so I don't see this putting much strain on the battery terminal.

I've physically tested the Blue Sea hardware and I do not have enough space inside the battery box for their 5502 Class T fuse holder (using a 250A fuse).


The 5191 MRBF holder has a single 3/8" (10mm) terminal hole which leaves a lot of slop when fastening it with a single 6mm bolt.



I've been thinking that I probably make something custom out of copper for the MRBF-style fuse but I wanted to see if someone knows of anything that already exists before I reinvent the wheel. Anyone been here before?


packrat

 

[740GLE]

I’d make a short custom bus bar to adapt the MRBF to the eve dual terminals

 

[HRTKD]

The argument against using an MRBF mounted on the cell terminal is that it puts strain on the cell terminal. Given the distance from the cell terminal that the cable would attach at, that can be a good amount of torque applied to the cell terminal.

I chose to run cable from the cell terminal to a Class T fuse holder mounted right next to the cells. It's a short run.

@740GLE's suggestion of a custom busbar for a MRBF is equally valid for a Class T fuse holder. For my 48v battery, I considered doing just that and had purchased copper bar stock to make the busbar. I ended up making the connection with a cable since there wasn't a good way to actually mount the fuse holder to the top of the cells.

 

[Didicoy]

I have the same question.
I'm upgrading to lithium and I've read not to use the MRBF because big number technical reasons, and only to use the type T but I see a lot of people using the MRBF.


So which type is the right type for lithium?

 

[SomethingAppropriate]

I have the same question.
I'm upgrading to lithium and I've read not to use the MRBF because big number technical reasons, and only to use the type T but I see a lot of people using the MRBF.


So which type is the right type for lithium?

If 48v and a parallel setup, class T is the only way.
If you have 1, 100ah or less, 48v battery, MRBF probably would work. NOT in parallel,

 

[Suijkerbuijk]

I have the same question.
I'm upgrading to lithium and I've read not to use the MRBF because big number technical reasons, and only to use the type T but I see a lot of people using the MRBF.


So which type is the right type for lithium?

Both .
For 12/24 its fine .
I use same mrbf holder .
Really that holder will have the same pressure on the cells connector like a lug on a cable .
So that is not a problem .

In series 36/48 volts and up i will not use them and go for t-fuse .

T-fuses fuse 20.000/25.000 aic 125volts

Mrbf fuse 10.000aic 12 volts (by 24 volts just 5000aic)

Personal its up to the user .
Driving in a RV or use a boat i go for a mrbf fuse .
Easy to replace and lot of car to boat shops sell them.
For a house i go for a t-fuse .

The moment i have multi parallel battery to a busbar.
I go for mrbf fuse from the battery to the busbar .
From the busbar to a t-fuses .
Thare is a lot of power from multi battery.

A mrbf fuse can handel 10.000aic.
A 100ah do about 1000ah .
So you can set a lot of parallel battery on a busbar .
But thare is no fuse from the battery to the busbar .
So for multi use and bms go stupid that mrbf fuse will save your compleet battery setup that is for the busbar .
It cut the power from the busbar and set that battery out of order from the parallel setup

 

[HRTKD]

Up until a few months ago the ABYC (American Boat and Yacht Council) did not allow an MRBF to be used directly on the battery terminal. There was a rumor that they were going to relax that restriction, but I have yet to hear if that happened. In a mobile environment where there will be vibration, the MRBF on the cell terminal is not a good idea. In a static environment where the cable attached to the MRBF has sufficient strain relief, it's OK but I still think the Class T Fuse is the way to go.

 

[Suijkerbuijk]

Up until a few months ago the ABYC (American Boat and Yacht Council) did not allow an MRBF to be used directly on the battery terminal. There was a rumor that they were going to relax that restriction, but I have yet to hear if that happened. In a mobile environment where there will be vibration, the MRBF on the cell terminal is not a good idea. In a static environment where the cable attached to the MRBF has sufficient strain relief, it's OK but I still think the Class T Fuse is the way to go.

Funny thare is no direct contact on a cell .
Inside the battery if you open it .
Thare is cable from the bms to a big nut.
You place that mrbf holder on that big nut .
That big nut its set in the plastic house of the battery.
So thare is no direct contact on a cell
But that is if you only use a singel mrbf fuse.
Thare are holder up to 5 mrbf fuse .
Wel that will have a problem.
Than again nothing in the way to make a support on that part dat help support it

For the rest mrbf are marine use and certification for it.
And use on small to big ships to use .
If somting had a problem than yearsssssss back it pop up on that case .
Even lead battery agm have nut and bolt systeem to connect a cable on it . (Not all lead battery have pool like a car battery )
What is use for years .

I think a ABYC engineering see spooks again .
I see that by new generation people that try to find a new wheel .

 

[Ohms_Cousin]

If 48v and a parallel setup, class T is the only way.
If you have 1, 100ah or less, 48v battery, MRBF probably would work. NOT in parallel,

when you say NOT in parallel - do you mean 16S2P for example? OR ......do you mean a number of 16S batteries connected to a bussbar in parallel ?

 

[Steve_S]

I use MRBF's on all my packs which are 7x280AH Packs all going to one common DC Busbars (8-post heavy).
All Packs have a 200A DC Breaker within. The 200A MRBF's are located at the Busbar using the standard bracket.
Personally I would never put such a Fuse within a Battery Pack (cannot see it and PITA to replace if something goes awry).
The most common installation is either on Battery Pack Terminal or close to it, alternately on the Common DC Bus depending on your system design. For Class-T and other fuses, ALWAYS use the correct holder/bracket !
Important detail: use the proper terminals. IE for M6 (1/4) Screws/Bolts, ensure the terminal hole is M6(1/4)
M6=1/4, M8-5/16, M10=3/8. Make sure the lug/terminal is as snug as possible. Using a 3/8 lug on 5/16 screw is NOT good !

A NOTE on ALL Fuses ! Regardless of type of fuse, they ALL add inline resistance and that varies with the Amperage Rating so do take that into account when calibrating your systems.

!!! Every Battery should have it's own Fuse/Breaker and NEVER EVER Pair battery packs onto 1 Fuse !

 

[Suijkerbuijk]

when you say NOT in parallel - do you mean 16S2P for example? OR ......do you mean a number of 16S batteries connected to a bussbar in parallel ?

He means if you use multi 48 volts battery in parallel.
Only a t-fuse can handel high volts .
A mrbf can only do this .
10.000 aic on 12v
7500 aic on 24v
5000 aic on 48volts .
Its not save to use a 48volts battery setup on a mrbf fuse.
100ah do about 1000a on 12v (lead battery a lifepo4 do about 1300a) aic
So yes with one 48volt 100ah you can do it.
Its stay in than range up to about 300ah on lifepo4.
After that you have to switch .

ABYC standard tell you to do so with lead battery that on the moment you go to 10.000a aic you can not use a mrbf fuse on 12 volts and need to switch to a t-fuses in the main connection cable line .

Than again multi 48 volts parallel with all battery on its own mrbf fuse will be fine to use.
The fuse is between the battery and the busbar .
No problem with lead battery .
But with lifepo4 change things .

Thare 2 different thinks what lifepo4 do and a lead battery do not.

One a lifepo4 have a bms that control discharge and charge.
Two a lifepo4 have a restart after short circuit up to 5 times ( means the bms try to connect discharge again )
Now that is the problem with fuse with a low aic.
On that moment you can have a arc spark .
Reason the bms have disconnect the power for that the fuse will melt compleet.
That is the reason we use a t-fuses in the main line by 48volts setup.

A t-fuses is a fast response fuse.
A mrbf fuse standard response fuse.
C20/anl fuse is standard or slow fuse.
Mega fuse is a slow fuse.

How slower the fuse is how les it burn down.

Wel the lead battery do not stop it have no bms.
So a lead battery burn in one go a fuse fast or slower no problem its gone.

So now we know how fuse works.

T- fuse 20.000 aic 125 volt minimum model.
Mrbf fuse do 10.000 aic by 12volt higher volts is lower aic
A c20/anl fuse do 5000/6000 aic on 12 volts higher is lower aic
Mega fuse are only 3000/4000 aic on 12 volts
And really its a fuse that you do not use on lifepo4 battery is even to weak for it 24volts setup.

So the best fuse .
T-fuses but it cost a lot but the only one for 48volts setup.

Mrbf fuse are fine op to 24volts .
Can ben use on 48volts on one battery use with low ah .

C20/anl fuse are good for 12/24 volt minimum.
Can be use in 48 volts but not recommended.

Mega fuse never use it and replace it for a c20/anl fuse for more safety.
Its just to slow to burn down.
Even for 12 volts systeem what is controle by a bms.

 

[Didicoy]

You guys rock.
I feel much better about my choice, I do hope OP also found his answer.

 

[Suijkerbuijk]

You guys rock.
I feel much better about my choice, I do hope OP also found his answer.

And that is ?

 

[S Davis]

I use MRBFs on my 12v packs, but with my custom buss bars it is a real solid connection.

 

[HRTKD]

I use MRBFs on my 12v packs, but with my custom buss bars it is a real solid connection.


View attachment 256846

That's a heck of a busbar!

 

[S Davis]

That's a heck of a busbar!

They are sized to pull 280amps, Erie Flex buss bar.

https://www.nvent.com/en-us/eriflex/products/nvent-eriflex-flexibar-advanced-tinned-copper-0

 

[Didicoy]

And that is ?

MRBF between each battery and the battery busbar with a single T type between the busbar and the load.

 

[Ohms_Cousin]

And that is ?

Ahhhh, "You Rock" - that means something similar to enjoying yourself in a coffee shop in Amsterdam. :-0

 

[Suijkerbuijk]

Ahhhh, "You Rock" - that means something similar to enjoying yourself in a coffee shop in Amsterdam. :-0

The Netherlands Amsterdam is dump place and a shit hole in hour country.
We are not proud on that city .
That is what most Dutch people think about Amsterdam.

Outsider that come to Amsterdam go only to place wat is fun , special make for those people on holiday.

 

[HRTKD]

The Netherlands Amsterdam is dump place and a shit hole in hour country.
We are not proud on that city .
That is what most Dutch people think about Amsterdam.

Outsider that come to Amsterdam go only to place wat is fun , special make for those people on holiday.

My son did a semester abroad in Maastricht and we made the trip to visit him there and other parts of the country. It was very nice. I didn't make it to Amsterdam except to go to the airport.

Anyhow, back to the topic: The form factor of MRBF is hard to beat. But the AIC numbers are certainly in favor of the Class T Fuse.

 

[Suijkerbuijk]

My son did a semester abroad in Maastricht and we made the trip to visit him there and other parts of the country. It was very nice. I didn't make it to Amsterdam except to go to the airport.

Anyhow, back to the topic: The form factor of MRBF is hard to beat. But the AIC numbers are certainly in favor of the Class T Fuse.

I thinks its for 12/24 systeem a t-fuses i a lot.
Special in a Rv , car , boat and
Even with 600ah you are not on that limit
And if it do, like will all ready tolt .
The cable can not handel it and burn down first.

Even for 48volts it do not work that great like people think see this information on the attack files.

And the link for the mrbf fuse time it need to blow

300A Ceramic MRBF Fuse, Car Boat MRBF Fuse, MRBF Automotive Micro Fuses, Automotive Micro Fuses

High quality All Inclusive Square Battery Ceramic MRBF Fuse 58V 30A 100A 200A 300A For Car Boat from China, China's leading 300A Ceramic MRBF Fuse product, with strict quality control Car Boat MRBF Fuse factories, producing high quality MRBF Automotive Micro Fuses products.

m.fuse-china.com

 

[HRTKD]

I inadvertently tested my Class T fuse in my 48 volt system. It blew right away when the CNN and MEGA fuses did not. When Littelfuse says it's a fast blow fuse, they weren't kidding.

 

[packrat1969]

Thank you Everyone for your replies and expansions on my original post. I always appreciate the new things I learn when I come here.
There seems to be some major concern with stress on the spot-welded aluminum battery terminal with regards to mounting an MRBF fuse holder directly to it. Especially in a mobile application like my RV. Does this apply if the doubled-up 4ga cable only spans the 3-6" from the +12V terminal to the bulkhead pass-thru terminal? The cable is fairly flexible.
If that's the issue, then I suppose I could move the fuse holder to the outside of the bulkhead pass-thru terminal. Though, a fuse in this location sort of defeats my attempt to make the battery "safer" if something horrible were to happen inside the case.

Ultimately, I do wish that someone could come up with a better Class T fuse/fuse bracket that could work with the form factor and terminal styles of these prismatic LiFePO4 batteries. Are there other form factors of Class T style fuses that would fit confined spaces better than the standard Blue Sea fare?

packrat

 

[Suijkerbuijk]

Thank you Everyone for your replies and expansions on my original post. I always appreciate the new things I learn when I come here.
There seems to be some major concern with stress on the spot-welded aluminum battery terminal with regards to mounting an MRBF fuse holder directly to it. Especially in a mobile application like my RV. Does this apply if the doubled-up 4ga cable only spans the 3-6" from the +12V terminal to the bulkhead pass-thru terminal? The cable is fairly flexible.
If that's the issue, then I suppose I could move the fuse holder to the outside of the bulkhead pass-thru terminal. Though, a fuse in this location sort of defeats my attempt to make the battery "safer" if something horrible were to happen inside the case.

Ultimately, I do wish that someone could come up with a better Class T fuse/fuse bracket that could work with the form factor and terminal styles of these prismatic LiFePO4 batteries. Are there other form factors of Class T style fuses that would fit confined spaces better than the standard Blue Sea fare?

packrat

You can always set a cable to a support part and set thare the mrbf fuse holder

See part list

https://www.amazon.nl/Gebildet-Stroomverdeling-Terminal-Positieve-Negatieve/dp/B0D66LJM88/ref=mp_s_a_1_39?crid=2WRIQGYBOE8M0&dib=eyJ2IjoiMSJ9.JytEBQbIUD6zLu8FJpCzoGSYYb5BYwK_T0VKe7pwjV9syFlASTyJjvDxdi8UZ7Oe-DzrOSmbXqCIYOrW9fcWW4-uZXafuHsO_I7SbpJzW5OhkiKds2TcHa0ZXN8fyLjX4KQsWSuBSzN0G5EryyVOsqnmeGnJS4VRk8UIn3yfDXwaxl_me8MlS1CoBxVgXOM-x7F69cY2qjIk2KlPhT_Jqg.veKayUTdOdJ_h7hgMguBu5AnOYWQ6qzWzplD5XIE2_w&dib_tag=se&keywords=busbar+singel+m8&qid=1732201675&sprefix=busbar+singel+m8%2Caps%2C128&sr=8-39

You only gone use that holder to set that mrbf fuse.
The cable on top of the mrbf fuse connection.
From the mrbf fuse you set that other cable

Done.
Unit is use for support not for a connection.
So that limit of 48volt 200a is not important.

Thare is a dubbel model from it

You can do this on a busbar to if you like.
Use the busbar for support for the mrbf holder.
So short cable to from battery to battery .

Do one thing sand paper so its really clean on the mrbf parts so it nice good connection.

 

[HRTKD]

Does this apply if the doubled-up 4ga cable only spans the 3-6" from the +12V terminal to the bulkhead pass-thru terminal? The cable is fairly flexible.

If there is proper strain relief for the cables then there is no issue.