48v Server Rack bank disconnect and circuit protection.

photonpirate

New Member
Joined
May 1, 2022
Messages
1
I've been planning the storage phase of my system with (6) 48v server rack batteries wired in two 15kW parallel strings then to a bus bar keeping them in parallel but as individual banks. I have 3 inverters that will be connected to the same bank pair. I'd like to add a disconnect for each bank to be able to take one out of service and still run off the other if needed.
The dead short protection will be provided by T-class fuses but I'm having difficulty determining the best product for the disconnect and over current protection. I've been looking at the product below:

Available on Amazon

ASI NDB1-125C125-2, Miniature Circuit Breaker, DIN Rail Mount High Current Circuit Breaker, 125A, 2 Pole, 240Vac, 60 Vdc, C Trip Curve

With a total of 22kW of inverter with a 2 48v 15kW banks, would I need to plan for over current breaker of at least 250A per parallel string? I understand I can parallel the double pole 125A breaker above to act as a 250A breaker.

I highly doubt that I'll ever come close to running all three inverters at even half the rating at the same time. The configuration is designed for redundancy and separate needs which will be managed strategically.

Unless I'm missing something, I think this will suffice.
I'd love to hear any other suggestions.
Thanks
 

ak1a

New Member
Joined
Apr 4, 2021
Messages
3
I've been researching options on the same type of question. Multiple battery banks of 6 units each with their own cutoff switches connected to bus bars for sharing with the inverters. My inverters can do up to 275 A at low voltage cutoff apiece. Signature wired theirs with a 200A breaker they sell on site and no disconnect for the entire bank. Their procedure is to switch off each battery, and when the entire bank is down, then switch the breaker. With this kind of procedure arcing is not an issue. I'd be willing to pay the money for DC rated safety disconnects that work under load but haven't found one yet. I remain interested in finding such a beast. Schneider sells a 275A breaker for use in their DC breaker panel, but it isn't designed for multiple breakers in the same panel to multiple batteries, as best I can tell. For now, I'm just assuming T class fuses adjacent to each bank going to their 200A breaker and a procedural shutdown. This would not accommodate the system's true capabilities.
 

RV10flyer

Photon Sorcerer
Joined
Mar 8, 2021
Messages
731
I have 10 batteries totaling 132 kWh. If I need to turn off all of them I have 10 breakers that I can turn off. Or I have a 250A breaker in each Sol Ark 12K. I would turn off the a/c load output breakers and the PV input switches first. I've turned the Chinese CHYTI 100 amp breakers on each individual battery off and on under a 10 to 40 amp load with no problems.
 
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