New to lifepo4. Need advice on a shunt and fuses.

[Deegore]

Hi, I've been running lead acid golf cart batteries for 15 years and am almost ready to switch to lifepo4.
I have 16 314ah Eve cells that just arrived from luyuan, along with a 200 amp jk bms with 2amp active balance.
I am in northern Minnesota and don't have any heated out buildings, so I plan to install the batteries in a utility room in my house.
I have been using cheap DC circuit breakers from Amazon, but reading that I should get something better.
I will be running a 3000 watt 48 volt inverter to power my house.
I am looking at a Blue Sea Systems 5191 Fuse Block Terminal with a 75 amp fuse between the batteries and the inverter.
Is that a good choice? I'm looking to keep my costs down, but also want to be as safe as possible.
Would I use the same fuses between the charge controllers and the solar panels, and the charge controllers and the batteries?
I currently have 2 60 amp charge controllers and 1000 watts of solar panels for my 12 volt system. I plan on adding 2000 watts of solar panels soon.
(The wife wants more power).
I have never had a shunt, but am told I should get one. Is this AiLi Battery Monitor an appropriate shunt?
I currently have my 12 volt system wired with 4 gauge copper wire. Can I safely hook everything up with that? The batteries will be about 15 feet from the solar panels.
Thank you

 

[DIYrich]

Fuses protect the wire. Use a class T fuse (blue sea has them) to protect the battery wire. In a dead short, the class t has a 10,000+ amp interrupt capability. Others could short closed and allow the ultra high current to pass.

The other wires can be protected with the fuse in your link.

 

[HRTKD]

With a single battery, the need for a shunt is less than if you had multiple batteries in parallel. However, the state of charge reported by the BMS can often be off because they aren't very good at accounting for low amp loads. A shunt does a much better job at that.

Yes, use a Class T. I have similar cells and the same BMS.

I prefer to have a circuit breaker on both sides of my solar charge controllers. This allows me to easily and quickly disconnect the solar charge controller from the system when I need to work on it or other components in the system. My circuit breakers come from MidniteSolar.com and go on a DIN rail.

 

[robbob2112]

Generally good prices on class T stuff

Blue Sea Systems 5007100 Ignition Protected Class-T Fuse Block 110-200A

Blue Sea Systems 5502100 Ignition Protected Class-T Fuse Block 225-400A

Notice there is a different size depending on the rated amps - they are not interchangable

 

[Deegore]

I'm confused about what size class t fuse to get. I think my setup won't have more than 60 amps max flowing through any party of it.
Does the class t fuse go between the battery and inverter and between the battery and charge controller?

 

[HRTKD]

I'm confused about what size class t fuse to get. I think my setup won't have more than 60 amps max flowing through any party of it.
Does the class t fuse go between the battery and inverter and between the battery and charge controller?

One Class T fuse between the battery and everything else. Then smaller, less expensive fuses or breakers between the components and what I call the common bus bars.

 

[Deegore]

Ok, so if my inverter can draw a max of 60 amps, and I have a 60 amp charge controller, would I want a 120 amp class t fuse?

 

[HRTKD]

Ok, so if my inverter can draw a max of 60 amps, and I have a 60 amp charge controller, would I want a 120 amp class t fuse?

No.

Taking just those two components into account (with no fudge factor for efficiency), you would want 60 x 1.25 = 75 amp fuse. The 1.25 multiplier is to ensure that you don't encounter any nuisance trips.

Your inverter will likely pull more than 60 amps. Taking the simple calculation of 3000/48 = 62.5 amps shows that it's a bit more than 60. But inverters aren't 100% efficient. You'll have to plug in your inverter's efficiency number. By default we use 85% efficient.

3000 / 48 / .85 x 1.25 = 92 amps. A 100 amp fuse (if it exists) is more appropriate. 125 amp fuses are probably what is available as the next step up.

You could also fuse for the max discharge of the BMS. So 200 * 1.25 = 250 amps. But if you KNOW that none of your loads will exceed the ~60 amp number from the inverter, the 250 amp fuse is overkill.

You'll want to keep in mind that the inverter will draw a huge amount of amps the first time it is connected. I had a 175 amp Class T fuse on my 48v battery (280 Ah cells, 200 amp BMS) that the capacitors on my Victron Quattro 48/3000 went right through. That was an expensive mistake. I implemented a pre-charge circuit that controls the capacitor surge so it doesn't blow the Class T fuse. I also increased my fuse size to 225 amps, just in case.

 

[Deegore]

Thanks for all the help.
Looking at wire size charts, 1/0 gauge wire is recommended for 125 amps.
My jk 200 amp bms has two 7 gauge wires to connect to the battery, which is the equivalent of one 4 gauge wire.
What gauge wire is appropriate to go from the battery to the class t fuse, to the bussbar?

 

[HRTKD]

I don't use the charts. Instead, I use a wire gauge calculator that takes into account different lengths of wire.

Interactive Wire Size Calculator

Battery Chargers, Inverters, Solar Components, and Wiring Supplies for Boats, RVs, and Off-Grid Applications.

baymarinesupply.com

Since I had plenty of it laying around, I used 2/0 to go from my cell terminal to the BMS, BMS to the battery box terminal, battery box terminal to the shunt.

 

[Deegore]

Great, it looks like 4 gauge will be fine.
Thanks for mentioning the pre charge circuit, I was not aware that could cause damage. It looks like I can get a 48v 25watt bulb to pre charge.
Does my drawing look ok?
Can I use This mrbf fuse block as a bus bar for the scc and inverter?

 

[HRTKD]

An actual circuit breaker between the solar charge controller and the battery/inverter will allow you to isolate the solar charge controller without pulling a fuse. That comes in handy when doing maintenance.

If your battery doesn't have a built-in switch then you'll want a switch between the battery and the Class T fuse. Something like the one below that is actually rated for 48v battery systems.

Battery Switch ON/OFF 275A - Victron Energy

The Battery Switch ON/OFF 275A is suitable for battery systems up to 48V. It has a unique ergonomic and aesthetic knob design.

www.victronenergy.com

Yes, the MRBF fuse block would work. It's rated for 58 volts. Make sure the MRBF fuses you buy for it are also rated for that voltage. However, eventually you're going to have more wires to connect to the system and you'll quickly find that there aren't enough studs on that block for your needs.

 

[robbob2112]

Rotated - I cant read when sideways

 

[robbob2112]

An actual circuit breaker between the solar charge controller and the battery/inverter will allow you to isolate the solar charge controller without pulling a fuse. That comes in handy when doing maintenance.

If your battery doesn't have a built-in switch then you'll want a switch between the battery and the Class T fuse. Something like the one below that is actually rated for 48v battery systems.

Battery Switch ON/OFF 275A - Victron Energy

The Battery Switch ON/OFF 275A is suitable for battery systems up to 48V. It has a unique ergonomic and aesthetic knob design.

www.victronenergy.com

Yes, the MRBF fuse block would work. It's rated for 58 volts. Make sure the MRBF fuses you buy for it are also rated for that voltage. However, eventually you're going to have more wires to connect to the system and you'll quickly find that there aren't enough studs on that block for your needs.

EDIT - I reread the diagram and understand the use now -- use the 3 position block
I agree with everything - except - MRBF is only rated at 2ka for the AIC at 48v --- so ideally the class T as close to the battery as possible or a breaker rated for 10ka AIC next to the battery - so the MRBF might be ok and might not interupt an arc.

Now you could use a 3 position MRBF fuse block to have enough studs to mount the other wires without stacking or a small bus bar. The class T does the grunt work and the MRBF protect individual branchs.

Blue Sea Systems 5194 Terminal Fuse Block for 3 Independent Circuits

from

https://assets.alliedelec.com/image/upload/v1631786560/Datasheets/6fe5ed5004b91724275098357f903bae.pdf

 

[Suijkerbuijk]

EDIT - I reread the diagram and understand the use now -- use the 3 position block
I agree with everything - except - MRBF is only rated at 2ka for the AIC at 48v --- so ideally the class T as close to the battery as possible or a breaker rated for 10ka AIC next to the battery - so the MRBF might be ok and might not interupt an arc.

Now you could use a 3 position MRBF fuse block to have enough studs to mount the other wires without stacking or a small bus bar. The class T does the grunt work and the MRBF protect individual branchs.

Blue Sea Systems 5194 Terminal Fuse Block for 3 Independent Circuits

from

https://assets.alliedelec.com/image/upload/v1631786560/Datasheets/6fe5ed5004b91724275098357f903bae.pdf

View attachment 255461

The ceramic fuse can not burn.
That is for mrbf and for anl fuse that have ceramic.
Thare are for anl fuse junk that have plastic house .
That one burn down house.
That plastic meld and burn around it by the arc

The vetus fuse cost a lot.
And have completed other specss than a normal anl fuse.
Encapsulated in glass to prevent fire is one of them.

Strip fuse (ANL / C20) - 40 Amp.

The strip fuse 40 Amp. are encapsulated in glass to prevent splatter and fire. Matches the fuseholder SECH100.

vetusonline.com

I have contact vetus about the icc specs.
The Moment i have it i share it here.
It can be a good replacement for other fuse to use

Personal i use this vetus model 65a for my Victron mppt 100/50a model . (Cost 25 euro)

 

[robbob2112]

Link to the vetus fuse? Haven't seen them

 

[Suijkerbuijk]

Link to the vetus fuse? Haven't seen them

See my reaction above thare is a link.

 

[Brucey]

Thanks for all the help.
Looking at wire size charts, 1/0 gauge wire is recommended for 125 amps.
My jk 200 amp bms has two 7 gauge wires to connect to the battery, which is the equivalent of one 4 gauge wire.
What gauge wire is appropriate to go from the battery to the class t fuse, to the bussbar?

Those 7 gauge wires are silicon insulated and rated for 200C. That's how they can handle 200A.