How to support 500A charge/discharge to battery?

[rhino]

I have a battery bus where all batteries are connected to. From there there is a positive and negative 4/0 copper going to busbars about 7 feet away where the charge controllers and inverters are connected to. That 4/0 battery cable is currently protected by a 250A MCCB that disconnects both the positive and negative. What is the best/safest way to increase the charge/discharge to 500A continuous while still having a disconnect and over current protection on the main battery cable(s)?

Solutions I've been thinking about:
1) 630A Dihool 2 pole breaker. Weary of getting a breaker from Amazon/Aliexpress and trusting the safety of it.
2) Two 250A Midnite DC Breakers connected to 2 separate 4/0 copper cables. This seems simplest but would only disconnect positive side. Not sure that is acceptable?
3) This 600A switch. I would still need current protection for it and not sure what would work best.

This is for "only" 20kW+ of PV power. Surely other people must be running into this issue with much larger arrays.

 

[Quattrohead]

Those Dihool breakers are very seriously heavy duty. I have 1 and will use more in the future.

 

[rhino]

Those Dihool breakers are very seriously heavy duty. I have 1 and will use more in the future.

You have those newer black ones?

 

[Rocketman]

Will you ever be charging or discharging at 500 amps?

If the max you will ever put through it is 250a then really you can fuse it for that. The bigger wire just reduces voltage drop. It doesn’t matter if the battery could produce 500a - except in short -circuit.

 

[Hedges]

You could run separate cables to each inverter, each with its own OCP.
Cables could connect to opposite ends of battery bus for half the current in the bus.

Assuming your 250A MCCB is 2-pole and each pole rated for the voltage, you could use one pole for each of two inverters.

I have 23kW of inverters, and I use two 350A class T fuses, each feeding two inverters. The inverters each has a breaker, so fuses are for short-circuit protection only.

 

[Nikg736]

This is ironic. I was just about to make a fresh thread, but maybe this is similar enough of a topic to get my question answered. Let me know if I am "hijacking" this one too much.
I'm currently building some Lifepo4 batteries for mobile audio use. Long story short, I have seen others on FB Marketplace advertising their "home made" versions. One is a 60ah and uses C-max batteries (which I think are lithium ion, not LFP) and person is claiming "can handle around 25,000 watts". To support that claim on 14.8-16.8v, one would have to pull around 1600A.
I'm just wondering what kind of wiring and bus bars would even support that? And can C-max batteries really deliver that kind of juice? Also, at 60ah of capacity (more 45-50ah real-world) running that wattage we are looking at maybe a few minutes of run time...not even enough to finish a song provided nothing melted, caught on fire or exploded.
I'm pretty certain this is the difference between theory and practice, but wanted some confirmation.
Thanks

 

[Quattrohead]

You have those newer black ones?

Mine is the single pole 300A in white.

 

[rhino]

Will you ever be charging or discharging at 500 amps?

Not 500A but over 400A charging and wanted some safety margin.

Assuming your 250A MCCB is 2-pole and each pole rated for the voltage, you could use one pole for each of two inverters.

the 250A MCCB is 2-pole and have it on both the positive and negative battery cables coming from battery bus. What if I just removed the negative and used both poles for positive? Would then add two 4/0 negative cables from battery bus that would bypass the breaker.

 

[ksmithaz1]

I feel you.

I like 2 cables, 2 fuses, 2 disconnects, put breakers on the inverter end. Run a 250A fuse on each. I don't allow charging over 300A total, unlikely I will ever even get there when I'm built out. I feed a 240v/100A panel. That's 24KW or 480A@50V give or take if I max it out, probably higher because of conversion. Just fusing the positive is fine AFAIK as long as it blows when it's supposed to. The cable requirements start to get stupid when you want 600A. I think its MCM300 or something free-to-air 4/0 is like 450 or something free-to-air. Fuggidaboutit if you want to stick it in conduit, it's gonna be $1000/ft.

I use the inverter breakers as disconnects for that side, and I did not put separate disconnects at the battery bus, just the fuses. My batteries are all rackmount, I just turn them all off individually if I need to take it down, but if you are DIY battery banks or just like to move things around a lot, not a bad idea to put one in front of the fuse.

Opinions are like *ssholes, everyone has one. I like to keep it simple, and I like to keep my wire sizes as small as possible because it's generally easier to work with. Kind of an eye opener when you start doing the math. . . Woa that's alottaamps!

 

[Hedges]

Here's mine, nicely split on the positive side. Negative (and jumpers between batteries) current goes through single 4/0 cable which is undersized. It feeds middle of busbar, so half current each way.

DIY Bus Bar

Im looking to make my own DIY Bus Bar that can pull 1000amps as buying one is expensive. Im looking to use it to connect a large battery banks. Can this be dune with supplies from hardware stores? Anyone know a good way to make on and what parts to use? The only one I can buy is this...

diysolarforum.com

I'm not worried about the undersize cable because it is only undersized for continuous current, and Peukert says my undersize battery bank will only last 20 minutes at full load. If bank was larger, like 1200 Ah 2V cells instead of 405 Ah 6V cells, it would have pairs of 4/0 cable.

 

[rhino]

Yes, this is all DIY batteries on a 6ft long Dewalt rack. Will soon consist of two 560Ah batteries plus a 260Ah battery. Each battery connected to a busbar attached to the rack. Just want some simple way to shut off all the batteries at once and protect that main cable(s) going from battery rack busbar to the system on the wall. I currently have that main cable protected with a 250A Noark MCCB but it is now undersized after I added a 14.4kW array for winter. I have to limit that array output to 100A since I have additional Victron charge controllers for another 9kW of panels on separate arrays.