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diy solar

Large Server Rack fusing

DIYrich said:
It is the nail that penetrates wires behind the wall and shorts Pos and Negative, or two wires where the insulation wore off, and shorted against each other.
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If you have wires burried in the wall it should have nailers over the studs below the sheetrock or the wires in metal conduit to prevent that.
 
chicagoandy said:
I'm in the process of acquiring the large Ruixu server rack. It's 10 48V 100Ah server racks assembled in parallel. It'll be paired with a Sol-Arc 15k.

I'll be attaching a fuse to the rack for safety. Currently I'm planning a 350A class-T fuse, the Bussman JJN-350. This has an AIC of 20 kAIC at 160 Vdc, 200 kAIC at 300Vdc. Presumably the AIC is less at 52V.
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The 200k AIC at 300v in the specs for that fuse is AC not DC.


In the spec sheet linked above it just shows 300 v (V what , why do they always have typos in the spec sheets???) but if you look farther down on the second page under (Electrical Rating ) it shows 200k AIC at 300 VAC

The AIC for VDC goes up as the VDC goes Down as a general rule , How much is the question and I have not been able to find the info for this fuse yet.

Edited to add yabert beat me to it.
 
Robert Ibe said:
The 200k AIC at 300v in the specs for that fuse is AC not DC.


In the spec sheet linked above it just shows 300 v (V what , why do they always have typos in the spec sheets???) but if you look farther down on the second page under (Electrical Rating ) it shows 200k AIC at 300 VAC

The AIC for VDC goes up as the VDC goes Down as a general rule , How much is the question and I have not been able to find the info for this fuse yet.

Edited to add yabert beat me to it.
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It isn't technically missing. Lowercase v indicates volts AC, while uppercase V indicates volts DC. Same with current - i is AC, I is DC.
 
hwy17 said:
I hope we get someone on youtube eventually trying to intentionally overwhelm a Class T with Lifepo4.

I bet it would be very very difficult to do, and if it was achieved successfully, would involve an impressive amount of copper. 8x 2/0 feeding into dinner plate sized bus bars, and then a knife switch the size that you'd power an industrial building with.

The stuff we work with, I bet you couldn't do it.
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For the batteries in question, this would also require the BMS and breaker to fail... 😁
 
Previously I had a 3P16S pack with the Class T fuse on the negative battery terminal bus bar. Recently I migrated to Pytes V5 rack batteries in two differerent racks. One is an external enclosure with four modules and a common ganged breaker on the leads to each modult. The other is an internal enclosure with three modules and no circuit breaker. Currently I have the Class T fuse in a junction box where the cables from the two enclosures combine into one cabel going to my SolArk. I have confidence that any internal short in a module would shut down that module or worse case the breaker on the external enclosure would open. The internal enclosure is another matter. It would have the same internal protection but in that case the modules are daisy chained with no separate breaker.
I light of the recent discussion on this thread and another thread, I am giving some thought to increasing the protection on the internal enclosure modules. I don't know if I will just add a class T fuse and a breaker or switch for maintenance or duplicate the topology of the external enclosure and run leads from each module to a ganged breaker.
 
sunshine_eggo said:
For the batteries in question, this would also require the BMS and breaker to fail... 😁
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This brand server rack battery doesn't have any internal overcurrent protection. No fuse or circuit breaker. So the only protectin is the BMS. There is a teardown video on current connected website or a link to one of Will's teardown of it.
 
yabert said:
You read this wrong. It's 160V DC vs 300V AC.
AC current is easier to break.
Braking current capability is increasing as voltage is lower.
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Thanks! They do not make parsing these documents easy for non-professionals. It intuitively makes sense that lower voltages would be easier to break, but I was going by what I understood in the doc. Higher AIC for Alternating Current also makes intuitive sense.

robbob2112 said:
This brand server rack battery doesn't have any internal overcurrent protection. No fuse or circuit breaker. So the only protectin is the BMS. There is a teardown video on current connected website or a link to one of Will's teardown of it.
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Yep, adding overcurrent protection was always in my plan, the recent thread just made clear I needed to get it right. :)
robbob2112 said:
You are mistaken - AIC is "Ampere Interrupting Capacity" ... This is the amperage of an arc it can extinguish
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Thanks, and yes - that definition is far more clear. In my defense, I did even verify the acronym with Google, and the incorrect one is very prevalent!
hwy17 said:
It's one pack inside the rack shorting internally, and then all the other packs feeding into that short that I'm thinking of. And in that case, the rack fuse does nothing. So it's really just a question of do you trust the breakers or not, and if you don't then the costly answer is every pack needs it's own Class T.
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This is an interesting one. My focus had been the rack fuse, but adding some for each battery does seem wise. Class T seems hard to fit, right now I'm thinking of adding a MRBF to each battery, it's much easier to keep the install clean. MRBF is rated to 58V, but only 2,000 AIC. That seems reasonable for a single battery, given that any additional current feeding it would also have an MRBF. In fact, in order to have uncontrolled short within a battery I would need at least 2 BMSs failing closed and 2 MRBFs failing closed.
hwy17 said:
I hope we get someone on youtube eventually trying to intentionally overwhelm a Class T with Lifepo4.

I bet it would be very very difficult to do, and if it was achieved successfully, would involve an impressive amount of copper. 8x 2/0 feeding into dinner plate sized bus bars, and then a knife switch the size that you'd power an industrial building with.

The stuff we work with, I bet you couldn't do it.
Click to expand...
I am hearing a very strong consensus that a single Class-T is the way to go for the rack. I'm happy to hear I was misreading the spec.

Interesting discussion, thanks everyone.
 
chicagoandy said:
This is an interesting one. My focus had been the rack fuse, but adding some for each battery does seem wise. Class T seems hard to fit, right now I'm thinking of adding a MRBF to each battery, it's much easier to keep the install clean. MRBF is rated to 58V, but only 2,000 AIC. That seems reasonable for a single battery, given that any additional current feeding it would also have an MRBF. In fact, in order to have uncontrolled short within a battery I would need at least 2 BMSs failing closed and 2 MRBFs failing closed.
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MRBF is better than nothing for sure.
 
FYI - Sol-Ark does not support closed loop communication with Ruixu. You will have to remove comms if you are using them before troubleshooting any operational issues.
 
chicagoandy said:
This is a bad look for you and your employer.
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Current Connected site clearly shows you want the Pytes if you want closed comms with solark as a supported configuration

There is no such claim for their Ruixu listing.


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hwy17 said:
It's not the battery rack overwhelming the Class T into an external short that really stands out to me. My gut feeling is that external shorts are rarely that good and low resistance to carry 10k amps. A short with that low resistance would probably require an intentionally designed shorting mechanism.

It's one pack inside the rack shorting internally, and then all the other packs feeding into that short that I'm thinking of. And in that case, the rack fuse does nothing. So it's really just a question of do you trust the breakers or not, and if you don't then the costly answer is every pack needs it's own Class T.
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The short answer for me is no and yes. As far as I am concerned a class T is required with the potential of these batteries, I am putting one in each of my new batteries.
 
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