Single vs. Multiple Class-T Fuses

[Will Prowse]

Does that mean you trust the server rack battery breakers to protect the individual batteries?

No, I use the BMS for over current protection. It's faster than any breaker. That is how it is designed to work. The DC rated circuit breaker is not for ocp. It's used as a disconnect. Have covered this in past posts. But you could argue that it is rated correctly to be used as ocp for individual packs. More redundancy is always nice.

 

[John Frum]

No, I use the BMS for over current protection. It's faster than any breaker. That is how it is designed to work. The DC rated circuit breaker is not for ocp. It's used as a disconnect. Have covered this in past posts. But you could argue that it is rated correctly to be used as ocp for individual packs. More redundancy is always nice.

That is where we differ.
I don't trust any fet based bms and since Signature solar doesn't stand behind their breaker, I don't trust the breaker either.

 

[740GLE]

We need a dead short test of these server rack batteries, how long will the BMS fry its brains out before the circuit breaker operates!!

You’d need a high current clamp meter to try and capture the peak current.

With all the inter cell connections and BMS Leads I’d wager the peak fault current is less than some are assuming.

 

[Will Prowse]

That is where we differ.
I don't trust any fet based bms and since Signature solar doesn't stand behind their breaker, I don't trust the breaker either.

This one doesn't even have a breaker:


The disconnect is a switch that turns on with the power button. No over current besides the BMS.

 

[Will Prowse]

That is where we differ.
I don't trust any fet based bms and since Signature solar doesn't stand behind their breaker, I don't trust the breaker either.

Can you comment on my T-Class fuse post which is pertinent to this thread? I really am not discussing the breaker at all. I am talking about multiple t-class fuses and how to separate towers.

 

[Will Prowse]

We need a dead short test of these server rack batteries, how long will the BMS fry its brains out before the circuit breaker operates!!

You’d need a high current clamp meter to try and capture the peak current.

With all the inter cell connections and BMS Leads I’d wager the peak fault current is less than some are assuming.

I honestly don't want to ? I am scared. I've had a lot of bad experiences with dead short tests in my past.

I have the equipment to do it right now. But yikes! Haha ??

 

[Will Prowse]

Just realized the new EG4 packs have DC rated circuit breakers. Anyone else here have the updated model and wish to share their breaker?

 

[John Frum]

Can you comment on my T-Class fuse post which is pertinent to this thread?

If you trust the BMS then you don't need high aic over-current protection for the feeders.
its nice to have but not necessary.
The feeder does need to be protected but a fuse of lesser breaking capacity would be fine.
Of course the fuse should ideally be as close to the start of the wire as possible.
The logic is that on over-current fault that is not a dead short the feeder fuse will blow cleanly.
If there is a dead short the BMSs will cascade trip.
A class t fuse would still be too slow to prevent the BMS cascade.

I really am not discussing the breaker at all.

Suit yourself.

I am talking about multiple t-class fuses and how to separate towers.

See my inline comment above ^

 

[John Frum]

Just realized the new EG4 packs have DC rated circuit breakers. Anyone else here have the updated model and wish to share their breaker?
View attachment 139210View attachment 139211

Cool, as soon as they update the manual I will be satisfied.

 

[Will Prowse]

Cool, as soon as they update the manual I will be satisfied.

I was not aware, will check that out.

I wish everyone actually used a t class fuse for each pack like the more expensive batteries. fortress power is a good example. Or the roypow ones.

 

[SignatureSolarJames]

Hi @John Frum

 

[John Frum]

Hi @John Frum

"Rated Working voltage Ue:DC60V/110V（1P）
Service short-circuit breaking capacity Ics:15kA/7.5kA.
Ultimate short-circuit breaking capacity Icu:20kA/10kA."

That is good.
Please update the manual to get rid of the weasel words.

 

[Will Prowse]

Glad to see it finally.

 

[Will Prowse]

This should be its own post. Or posted in resource section. Thank you James

 

[SignatureSolarJames]

"Rated Working voltage Ue:DC60V/110V（1P）
Service short-circuit breaking capacity Ics:15kA/7.5kA.
Ultimate short-circuit breaking capacity Icu:20kA/10kA."

That is good.
Please update the manual to get rid of the weasel words.

Or you could take the fact that the UL passed the pack as indicating that it is the proper fuse

 

[John Frum]

For reference this is the manual bit that I'm referring to.

Single vs. Multiple Class-T Fuses

MRBF has enough breaking capacity for 12 volts lfp batteries. Probably not enough for 24 volts and definitely not enough for 48 volt lfp batteries. How big is the wire and what is the insulation temperature rating? The MRBF I am looking at is - Amperage: 125A Maximum Voltage: 58V DC...

diysolarforum.com

 

[John Frum]

@SignatureSolarJames @Will Prowse ^

 

[SignatureSolarJames]

Their manuals include this disclaimer
"The included breaker is not a guarantee of battery protection. Size and install the correct over
current protection for conductors and battery if not included with the product." -- https://signaturesolar.com/content/documents/EG4/EG4-LL 48V-24V Manual-1.2.0.pdf

We were trying to address the potential for combined wires to carry more than the rated amperage. better words could have been used but clearly, we are referring to things "not included with the product" which disqualifies interpreting this to mean the battery breaker is not DC-rated.

this thread is very misleading and frankly defamatory in the comments saying that Chint says the breaker is not for DC. please clean up the mess in your previous comments @John Frum. tech support is already busy and this will plug the lines with nutty breaker questions next week

 

[Will Prowse]

Nope, not when the manual indicates you don't stand behind the breaker.

Where does the manual state that? They told me it was DC rated over a year ago.

I just don't like to state opinions and wait till we get the data sheet.

Now we have it. I couldnt recommend the packs unless it was DC rated. We had a big issue with this when I got my first pack. I should have posted the data sheet here or in resource section.

 

[John Frum]

Where does the manual state that? They told me it was DC rated over a year ago.

I just don't like to state opinions and wait till we get the data sheet.

Now we have it. I couldnt recommend the packs unless it was DC rated. We had a big issue with this when I got my first pack. I should have posted the data sheet here or in resource section.

"The included breaker is not a guarantee of battery protection. Size and install the correct over
current protection for conductors and battery if not included with the product." -- https://signaturesolar.com/content/documents/EG4/EG4-LL 48V-24V Manual-1.2.0.pdf