NOW we know why there has been such a class T shortage...Gotta love these fuse discussions. “ opinions are like A…”
Me, I put a class T fuse between every fricken cell!
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NOW we know why there has been such a class T shortage...Gotta love these fuse discussions. “ opinions are like A…”
Me, I put a class T fuse between every fricken cell!
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An MRBF fuse does not have the breaking capacity for your intended purpose.The MRBF I am looking at is -
The wire is 2/0 with 105C rating.
- Amperage: 125A
- Maximum Voltage: 58V DC
- Interrupt Capacity: 2000A @ 58V DC
The article you referred to states the breaking capacity and the interpret rating are one in the same.An MRBF fuse does not have the breaking capacity for your intended purpose.
Breaking capacity - Wikipedia
en.wikipedia.org
Because you need ~10,000 amps breaking capacity at 58 volts or betterThe article you referred to states the breaking capacity and the interpret rating are one in the same.
The fuse I mentioned has Interrupt Capacity: 2000A @ 58V DC.
Why wouldn't that work?
Class t or BS88 or something else that meets or exceeds the specs above ^If it doesn't work, then what should I look for?
Have my inline responses in this message cleared up your remaining confusion?Sorry for the questions, I simply don't understand.
Give it 1000a and see it it lasts as long!!Yes. I saw James' video. Seems like a long time to go at 200 amps. What do y'all think?
Yes, thank you.Because you need ~10,000 amps breaking capacity at 58 volts or better
Class t or BS88 or something else that meets or exceeds the specs above ^
Have my inline responses in this message cleared up your remaining confusion?
DANG ! ! ! ! ! !Because you need ~10,000 amps breaking capacity at 58 volts or better
Class t or BS88 or something else that meets or exceeds the specs above ^
Have my inline responses in this message cleared up your remaining confusion?
Most time I see a battery BANK being built, people don't fuse each battery *at all*.It's standard, recommended practice by everyone: this is also what Victron recommends, and is the way it is shown in documentation from e.g. Mersen (page 19 for example), ETI (this doc, page 35), etc. Doesn't have to be a Class T, but a fast acting fuse is recommended.
Cells make up a battery, multiple batteries make up a bank. Doesn't matter how many you add, it's still a bank.
I 100 agree with Keeping Fuses as close to battery/bank as possible. Seeing someone have a rack of batteries connected to a busbar and unfused wires going multiple feet before the first fuse makes me.... itchy.To address the broader point of why I think its most important to have a high breaking capacity fuse as close as possible to the battery positive terminal is to keep the electrolyte inside the battery.
I have found something!
This report tests short circuit behavior of a 5Ah and 160Ah LiFePO4 cell. There is not enough detail of the test procedure used to be entirely conclusive. But It seems that the short circuit current for a single LFP cell could be in the range of 6C to 10C.
This should give people some idea of what they need to be prepared for.
I.e if you have a single string of 100Ah cells (12V, 24V, 48V it doesn't matter) you are looking at a short circuit current as low as 600A or up to 1000A. Therefore you need to make sure your fuse would trip for a fault that's as low as 400-500A in a reasonable time. And is able to handle well in excess of 1kA (I wouldn't go any lower than 4kA rated fuses or MCBs).
This is good because it means that the MCBs in the server rack batteries are probably fit for purpose.
Update: My friend contacted EVE (as we currently have a combined order in for 120 LF280Ks) and asked what the prospective fault current is. Their immediate response was 2000-4000A. I have asked if they have any documentation around this.
That works out to 7-15C
Signature Solar was (is?) selling "ready to go" rack + batteries with a busbar, and no fusing per battery besides the breaker. And I'm fairly sure I've seen similar offering elsewhere. Now, I'm not saying I agree, but I'm also not sure I agree with a Class-T per battery, especially the 100AH ones; since if you do have one per battery each fuse only needs to break the amps FROM a single battery (if you have a short or fault in a battery it is no longer the upstream device).
Correct. Which is well within the capability of a Class T fuse or MCCB.So at 7-15C, a rack of 6 100AH batteries is 4,500-9,000A. I'd personally even double that expectation for the bank fuse.
That was me.Someone (in this thread?) was trying to calculate actual dead short amps but there seemed to be a lot of "assuming such and such" :-/
Their manuals include this disclaimerBecause they consider that breaker good enough.
Agree.Personally what I would love to see in these server rack batteries is a mounting spot for a fuse directly on the battery with clear instructions to not connect on the unfused side.
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
Is this cells or batteries?Update: My friend contacted EVE (as we currently have a combined order in for 120 LF280Ks) and asked what the prospective fault current is. Their immediate response was 2000-4000A.
IMO it is worse than useless.Nice - so the breaker gives people a false sense of security, as I feared.
ah yes but they also market that same CB as and “added safety” feature. Almost seems like that needs a little astrick, or a question mark after it, lol.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