Need a 350A Circuit Breaker. . Help.

[ManKzin]

Think of adding a 350A Circuit Breaker, but can't find one that doesn't make me nervous. I have three 12V 300AH 200A BMS batteries in busbar parallel, where it then goes off in 2 directions. The first with a 110A Class T off the + Bus Bar goes to the 12V 100A load accessories and 80A MPPT. The second direction with a 350A Class T off the + Bus Bar goes to a manual disconnect (Rated 350A continuous) and then to a 3000W inverter. Was wondering if I should put a circuit breaker that is 350A either 1 Pole or 2 pole, somewhere along this line before the inverter. Should I put a circuit breaker along here or not. Forgot to mention the batteries will have 250A MRBF on each one.

Looking for a product recommendation, If i should have one.

 

[robbob2112]

I would put a 250a MCCB breaker on each of the batteries... 2-pole so you disconnect both lines. In a pinch you turn off all three batteries. The class T are quick protection, the MCCB are slower protection and also a means of disconnect.

 

[OffGridForGood]

I have three 12V 300AH 200A BMS batteries in busbar parallel,

are these lithium iron phosphate batteries?
As @robbob2112 already said - when you have more than two batteries in parallel - they should each have protection so the others can't all feed back to a short in one.
Also:
3kW is high for a 12 v system. Have you considered maybe you have out-grown 12v?

 

[ManKzin]

are these lithium iron phosphate batteries?
As @robbob2112 already said - when you have more than two batteries in parallel - they should each have protection so the others can't all feed back to a short in one.
Also:
3kW is high for a 12 v system. Have you considered maybe you have out-grown 12v?

Yes all three are lifepo4. Was thinking about it. And still could do it later down the road. The person that helped me design the system, want to see it through, and see how it went. Think we got it and I have a lot of safety precautions in it. The breaker is just an afterthought

 

[ManKzin]

I would put a 250a MCCB breaker on each of the batteries... 2-pole so you disconnect both lines. In a pinch you turn off all three batteries. The class T are quick protection, the MCCB are slower protection and also a means of disconnect.

I saw on one of the threads saying that. Any particular MCCB that you have in mind? Cause I ain't going to get one of those cheap breakers, those are a fire hazard.

 

[RV8R]

I prefer “fuse protection” & a “manual switch” over a “breaker switch”.

Blue Sea makes decent switches;






The 4 position switches can be extremely useful.

Some of these switches are HD & 600 amp continuous rated.

AC & DC are different animals. This video shows why ,,, 1 minute in he switches the AC to DC & this will show you why your “Breaker Switch” might be better off as a “Switch” & “Fuse” instead. The video is 220v, but you will get the point;

You are asking a lot out if a “Breaker Switch” to combine both the fuse “protection” & switch (open/close circuit) all in one device ,,, with DC.

You see, a breaker switch “for the protection side of the equation” has to be able to perform under load. That in DC can create multiple issues ,,, crappy “contact” & increases resistance being just one problem.

Here is a thread with a “non-charging DC2DC issue;

https://www.promasterforum.com/posts/878550/

 

[ManKzin]

I prefer “fuse protection” & a “manual switch” over a “breaker switch”.

Blue Sea makes decent switches;

View attachment 260733

View attachment 260734


The 4 position switches can be extremely useful.

Some of these switches are HD & 600 amp continuous rated.

AC & DC are different animals. This video shows why ,,, 1 minute in he switches the AC to DC & this will show you why your “Breaker Switch” might be better off as a “Switch” & “Fuse” instead. The video is 220v, but you will get the point;

You are asking a lot out if a “Breaker Switch” to combine both the fuse “protection” & switch (open/close circuit) all in one device ,,, with DC.

You see, a breaker switch “for the protection side of the equation” has to be able to perform under load. That in DC can create multiple issues ,,, crappy “contact” & increases resistance being just one problem.

Here is a thread with a “non-charging DC2DC issue;

https://www.promasterforum.com/posts/878550/

View attachment 260737

Great video. Gives a nice visual. I had a Blue Sea 600A a bit ago, but decided to go with the 350A manual switch as my main switch. Though my system is designed to be a 3000W, I don't plan on going over 2300W.

 

[robbob2112]

I have seent that video before - it is demonstrating the arc length from DC.

That said - if a breaker is rated for DC it has magnets to pull the arc sideways into a set of arc chutes - arc chutes are metal plates that break the arc along multiple places.

Quality DC breakers all have this. In the ones that are polarized they can only break the arc in one direction. In non-polarized ones the arc chutes are arranged in such a way that they break the arc in multiple directions.

DC 200A Circuit Breaker Battery/Solar Disconnect – Ships now – Watts247 Affordable DIY Solar Power

watts247.com

Which seem to be relabeled DiHool breakers from their line with lower AIC

This is the higher AIC and voltage rating version - black case

Amazon.com

They can be had off aliexpress for about 1/2 that cost - I have several brands that I bought and intend to test to see how well they work. By testing I mean I'll run current through them and switch on/off a bunch while monitoring the contact resistence and with a thermal camera. From how solid they are built I am not worried about it. Once done I'll open them up and see what they look like. Well, I'll open the cheapest one or will decide if I want to open them up based on testing.


I have one of these

https://www.walmart.com/ip/Dc-Circu...eaker-Mccb-Solar-Battery-Pv-System/5065764149

If you want to find this type breaker used on ebay they typically go for $150ish for ABB, Eaton, or Schneider - it just varies by day

I have 2 of these on order that I will use on one of my inverters - the 250amp version

https://www.aliexpress.us/item/3256805292372148.html

One note on the difference betwen switches and breakers - you can turn a DC breaker off and on with current flowing with no damage.

With the switch there is a warning on them to not switch them with current flowing. You can do it so many times and it will arc and damage the contacts - I haven't seen any testing on how many times you can do it

 

[siegex]

Think of adding a 350A Circuit Breaker, but can't find one that doesn't make me nervous. I have three 12V 300AH 200A BMS batteries in busbar parallel, where it then goes off in 2 directions. The first with a 110A Class T off the + Bus Bar goes to the 12V 100A load accessories and 80A MPPT. The second direction with a 350A Class T off the + Bus Bar goes to a manual disconnect (Rated 350A continuous) and then to a 3000W inverter. Was wondering if I should put a circuit breaker that is 350A either 1 Pole or 2 pole, somewhere along this line before the inverter. Should I put a circuit breaker along here or not. Forgot to mention the batteries will have 250A MRBF on each one.

Looking for a product recommendation, If i should have one.

An isolation switch and a Class T 350a fuse

 

[RV8R]

Think of adding a 350A Circuit Breaker, but can't find one that doesn't make me nervous. I have three 12V 300AH 200A BMS batteries in busbar parallel, where it then goes off in 2 directions. The first with a 110A Class T off the + Bus Bar goes to the 12V 100A load accessories and 80A MPPT. The second direction with a 350A Class T off the + Bus Bar goes to a manual disconnect (Rated 350A continuous) and then to a 3000W inverter. Was wondering if I should put a circuit breaker that is 350A either 1 Pole or 2 pole, somewhere along this line before the inverter. Should I put a circuit breaker along here or not. Forgot to mention the batteries will have 250A MRBF on each one.

Looking for a product recommendation, If i should have one.

On my 12vdc systems with an inverter, I like to use double MRBF holders directly on the battery positive terminals. Then I like to split those double fuses into 2 sides of the DC system;

1) Inverter or Inverter/Charger (Think Mega Amps)

&

2) Everything Else (Think Lower than Mega Amps)



I want to expand upon what @robbob2112 wrote above & maybe explore this a little;



So in regards to a “breaker switch” & “no damage” ,, I believe breakers are manufactured for turning off under load, but I do not assume “no damage” or in other words an acceptable amount of wear & tear occurs. In Aviation we say “Any landing where the aircraft can be reused is a good landing” & really we just say that to make ourselves feel good . Even with breakers, I would reduce (eliminate) the loads before manually turning off.

My experience with aircraft & breaker/switches in 12vdc, is they can be susceptible to “resistance” where a fuse & switch less so. So think voltage drop.

It is always a good practice to eliminate or greatly reduce the loads prior to “disconnecting”, even to just be good to the equipment.

 

[robbob2112]

An isolation switch and a Class T 350a fuse

This one is well made - but only 320amps - might be good to have it trip before the class T blows...

Amazon.com

Upsize the wire a touch and the class T and you can use this one - shunt trip lever available so remote trip is possible.

Amazon.com

I have several of these and have taken them apart to verify construction - they are well made and there is a 350amp version -- and you can get them with a remote-trip coil if you want to be able to shut things down from a remote switch.

https://www.aliexpress.us/item/3256803106586727.html

This is not so well made - I wouldn't use it for anything but a switch - it lacks lubricant at key points and the arc chutes are less well done. The fit and finish looks like the case was a reject from the better brands. A touch oversize and not smooth alignment with the bottom side. Screws for attaching wires seem to be less well formed.

https://www.aliexpress.us/item/3256806810959675.html

There is another brand labeled BAOYI - seems to be the same and less well made

Pictures of teardown here on the last one
MCCB teardown


Note - with any of the 2P MCCB breakers they come with a pair of vinyl square tabs.... these fit down into the slots between the poles to keep them isolated better.


And I do use the 2P version rather than the 1P version -- I like breaking both poles from the batteries at the same time.

I did have a discussion with someone about it being required or not and we agreed to disagree. That was with regard to a RV build and I thought it should be 2P and he said no RV on the planet comes with 2P ... anyways right or wrong I like the 2P for any application... To me it is a floating system without a ground reference so it needs to disconnect both poles. And in my mind a RV that isn't plugged in isn't grounded unless there is something about the leveling jacks that provides an earth ground... but in that case what about van builds that don't do leveling

 

[jcollman]

On my 12vdc systems with an inverter, I like to use double MRBF holders directly on the battery positive terminals. Then I like to split those double fuses into 2 sides of the DC system;

1) Inverter or Inverter/Charger (Think Mega Amps)

&

2) Everything Else (Think Lower than Mega Amps)



I want to expand upon what @robbob2112 wrote above & maybe explore this a little;

View attachment 278851

So in regards to a “breaker switch” & “no damage” ,, I believe breakers are manufactured for turning off under load, but I do not assume “no damage” or in other words an acceptable amount of wear & tear occurs. In Aviation we say “Any landing where the aircraft can be reused is a good landing” & really we just say that to make ourselves feel good . Even with breakers, I would reduce (eliminate) the loads before manually turning off.

My experience with aircraft & breaker/switches in 12vdc, is they can be susceptible to “resistance” where a fuse & switch less so. So think voltage drop.

It is always a good practice to eliminate or greatly reduce the loads prior to “disconnecting”, even to just be good to the equipment.

I'm doing what you suggest with my modular system.

My question, similar to the OP, is whether I really need the isolator for such a small array.

Do I?

 

[RV8R]

I'm doing what you suggest with my modular system.

My question, similar to the OP, is whether I really need the isolator for such a small array.

Do I?

So if you do not have to satisfy any codes

Your array is;




PV Max 60.1V & how amps ?

Seems l saw 17 amps in one of your posts ?

Regardless;

I have the same Victron 100 | 50 MPPT & you can with the software turn the “charging” off ,,, thus I assume no load

So if you are diligently in turning the “load off” before say separating ( I prefer Anderson style connectors ) then I don’t think you “need” a disconnect switch. But that is just my personal level of risk, not code or “the right thing to do”.

Also, there are a lot of factors in that choice, 1 factor is who would be separating the “Anderson” or PowerPole Connection ,,, if it is you & you know what you are doing fine, but if someone else might be performing that task & would mistakenly do it under load ,,, not good.

If using Anderson’s even for the MPPT, maybe a different colour maybe ,,, Yellow for Sun .

 

[jcollman]

So if you do not have to satisfy any codes

Your array is;

View attachment 279039


PV Max 60.1V & how amps ?

Seems l saw 17 amps in one of your posts ?

I compute 19A, though that doesn't take into consideration temperature max/min.

Regardless;

I have the same Victron 100 | 50 MPPT & you can with the software turn the “charging” off ,,, thus I assume no load

So if you are diligently in turning the “load off” before say separating ( I prefer Anderson style connectors ) then I don’t think you “need” a disconnect switch. But that is just my personal level of risk, not code or “the right thing to do”.

Also, there are a lot of factors in that choice, 1 factor is who would be separating the “Anderson” or PowerPole Connection ,,, if it is you & you know what you are doing fine, but if someone else might be performing that task & would mistakenly do it under load ,,, not good.

Good point.

If using Anderson’s even for the MPPT, maybe a different colour maybe ,,, Yellow for Sun .

I considered that but decided against it - maybe I should revisit the SCC connector colors.

 

[ManKzin]

On my 12vdc systems with an inverter, I like to use double MRBF holders directly on the battery positive terminals. Then I like to split those double fuses into 2 sides of the DC system;

1) Inverter or Inverter/Charger (Think Mega Amps)

&

2) Everything Else (Think Lower than Mega Amps)



I want to expand upon what @robbob2112 wrote above & maybe explore this a little;

View attachment 278851

So in regards to a “breaker switch” & “no damage” ,, I believe breakers are manufactured for turning off under load, but I do not assume “no damage” or in other words an acceptable amount of wear & tear occurs. In Aviation we say “Any landing where the aircraft can be reused is a good landing” & really we just say that to make ourselves feel good . Even with breakers, I would reduce (eliminate) the loads before manually turning off.

My experience with aircraft & breaker/switches in 12vdc, is they can be susceptible to “resistance” where a fuse & switch less so. So think voltage drop.

It is always a good practice to eliminate or greatly reduce the loads prior to “disconnecting”, even to just be good to the equipment.

On my 12vdc systems with an inverter, I like to use double MRBF holders directly on the battery positive terminals. Then I like to split those double fuses into 2 sides of the DC system;

1) Inverter or Inverter/Charger (Think Mega Amps)

&

2) Everything Else (Think Lower than Mega Amps)



I want to expand upon what @robbob2112 wrote above & maybe explore this a little;

View attachment 278851

So in regards to a “breaker switch” & “no damage” ,, I believe breakers are manufactured for turning off under load, but I do not assume “no damage” or in other words an acceptable amount of wear & tear occurs. In Aviation we say “Any landing where the aircraft can be reused is a good landing” & really we just say that to make ourselves feel good . Even with breakers, I would reduce (eliminate) the loads before manually turning off.

My experience with aircraft & breaker/switches in 12vdc, is they can be susceptible to “resistance” where a fuse & switch less so. So think voltage drop.

It is always a good practice to eliminate or greatly reduce the loads prior to “disconnecting”, even to just be good to the equipment.

I actually had some help in the finally design and went with doing two legs coming off of a parallel Positive BusBar (All positive are equally length) , one with only the 3000W inverter with a 350A Class T Fuse and the on the other leg which has 100A Fuse Box (Total of Amps of all accessories is about 38A), 60A AC -DC charger (all device will be turned off while charging), and in the near future a 80A MPPT Controller. (Need permit).
I will post my build and finally portable cart design once it is all out together, which should have been completed today. Unfortunately it won't as i broke the isolation switch for the 300A leg by over tightening, though on accident as the lug had some play on it. I should have used a lock washer to hold it steady with the bolt, but of course I realized that until after it broke. So now it will probably be this weekend and then I will see if it catches fire or not. .

Shouldn't of course my wire management is pretty solid with no 4/0 AWG wires positive and negative crossing one another. The only ones that cross each other are the 12V accessories wires and those are separated whenever possible.

 

[RV8R]

I actually had some help in the finally design and went with doing two legs coming off of a parallel Positive BusBar (All positive are equally length) , one with only the 3000W inverter with a 350A Class T Fuse and the on the other leg which has 100A Fuse Box (Total of Amps of all accessories is about 38A), 60A AC -DC charger (all device will be turned off while charging), and in the near future a 80A MPPT Controller. (Need permit).
I will post my build and finally portable cart design once it is all out together, which should have been completed today. Unfortunately it won't as i broke the isolation switch for the 300A leg by over tightening, though on accident as the lug had some play on it. I should have used a lock washer to hold it steady with the bolt, but of course I realized that until after it broke. So now it will probably be this weekend and then I will see if it catches fire or not. .

Shouldn't of course my wire management is pretty solid with no 4/0 AWG wires positive and negative crossing one another. The only ones that cross each other are the 12V accessories wires and those are separated whenever possible.

I’m more visual than “read” a design, so I might miss the understanding “reading” your comments above.

Look forward to seeing your project .

 

[ManKzin]

---

I’m more visual than “read” a design, so I might miss the understanding “reading” your comments above.

Look forward to seeing your project .

Understood. I am able to see things visually by reading something, if I have knowledge of a process. For example I used to own my own flooring business and if a client wanted a particular design I had to visualize what they wanted. Doing this allowed me to charge more per square foot. If client provided the full design it usually was a $0.25 more, if we both figured out a pattern it was $0.35 more, if it was my own design $0.50 more. With electric I am still learning to do my knowledge is now semi-basic, since my first built is actually working. That I will be posting to this site, though if you can't wait check out the video I put on YouTube search 12v 3000w solar generator system and it should pop up. There is no links as is the policy of this site. Though I do mention Will and his book and this forum