Merged LiFeYPO4 1000Ah Winston prismatic cells and all electric galley...

[newhaul]

Originally Posted by CaptainRivet

The fuse you linked has an interrupt rating of only 3000A but your 250AH LFP bank has a dead short capability of 15000A till 25000A (depends on thi internal reistance of your cells typically somewhere between 8 and 20 milliohm) means if LFP gets shortend your 250A breaker will melt close and won't interrupt any more.
And your insurance surveyor has clearly no idea what he/she is inspecting here. If US have a look at the small print of the report as US surveyor have the ability to completely exclude all liability for their reports and work. Means if your boat burns down and during damage inspection the reason is a melted closed breaker that has an insufficient interrup rating (clearly and without any doubt the case and this will be in 99,9% also the reason) you are screwed and coverage refused....and his report you can use as toilet paper...
Also suggest to measure the voltage drop on this breakers when you pulling max amps... I bet it will be huge.
And the real car hifi freaks won't use these crappy breakers... I was in that scene for 20years and made democars for some of their manufacturers of car audio equipment. And my experience with these breakers is that from 150A on they really have half of their rating in reality.
They are good till 80A, mainly because you can use them as interrupt switch too which gets frequently used, i use one of them in 60A for the watermaker.

To many inconsistencies in your post to point out but I will go with the inspector for my insurance company here in my country and on my boat . He signed off on it so they would have to pay off on it .

And it's a breaker not a fuse.

[CaptainRivet]

Originally Posted by LeighC

Hi All,
I have bought one of these https://www.ebay.com.au/itm/384692313682 Have not connected it yet but looks & feels very sturdy, not marine listed though. Manual switch off very strong to switch off. Fairly large though.
Rated at 250A DC, connecting to Victron Easy Solar 48v/ 5000VA. for 28KW LiFePo4 off grid house system
Will report on how it goes as soon as system is commissioned.
Cheers - Leigh

How is your bank build, mainly how many cells in parallel, how big? 28kw with 48V is a 580AH bank... Did you calculate the dead short potential of your bank, means how much amps will it deliver when you short it....
25kA can be ok but on the limit or above depending on the internal resitance of your bank and how many cells are paralleled.
How are the contacts protected against corrosion taht will apear in short time due to salty air that reaches everything thats not sealed off?
Looks pure cooper means you need to clean all contacts up and seal them with eg battery pol grease or liquid rubber.

[CaptainRivet]

Originally Posted by newhaul

To many inconsistencies in your post to point out but I will go with the inspector for my insurance company here in my country and on my boat . He signed off on it so they would have to pay off on it .

And it's a breaker not a fuse.

So point out the inconsistency please.
Breaker or fuse doesn't matter if it comes to the specs and function when they are real. Only difference is fuse need to be replaced while a breaker it can be reenganged by fliping the switch.
A breaker has simply to small distance between the contacts to reach interrupt current of more then 2000A.. And thats the weak point of breakers as this short distance gets brigded by a lightbow and melts closed above 2000A.
the NH fuses have plenty space and isolation, enforced my the gas inside the ceramic body and ceramic itself is a perfect isolator. Well and thats all needed to reach 50kA interrupt rating.

Is the surveyor that signed off employed by the. Insurer? If not have a look at the small print what thats worth...

[LeighC]

I have 32 280AH cells connecting in 2P16S
Cells are reading around 0.17mΩ
I am 250 KM from the ocean for this residential farm house & not in a salty area.
Might use some desiccant crystals around, I am using a decommissioned coolroom with batteries in next compartment away from electronics & will have some ventilation.
I have a lot of bare copper around & none has turned green.
I suppose silver contacts would have been good but it looks good for the price
I do have Alminox grease to help prevent corrosion.
I am using a TAO BMS so trying to do the right install.
Getting a 52VDC rated disconnect switch is not that easy either.

[newhaul]

Originally Posted by CaptainRivet

So point out the inconsistency please.
Breaker or fuse doesn't matter if it comes to the specs and function when they are real. Only difference is fuse need to be replaced while a breaker it can be reenganged by fliping the switch.
A breaker has simply to small distance between the contacts to reach interrupt current of more then 2000A.. And thats the weak point of breakers as this short distance gets brigded by a lightbow and melts closed above 2000A.
the NH fuses have plenty space and isolation, enforced my the gas inside the ceramic body and ceramic itself is a perfect isolator. Well and thats all needed to reach 50kA interrupt rating.

Is the surveyor that signed off employed by the. Insurer? If not have a look at the small print what thats worth...

Yes employed by the insurer .
Things are handled differently in different countries. Don't forget this is a world wide forum. Not everything needs meet nanny state rules. Just best practice.

BTW where do you imagine the dead short happening that won't be sensed and dealt with by the BMS and or the monitoring Guage shunt?

[CaptainRivet]

Originally Posted by newhaul

Yes employed by the insurer .
Things are handled differently in different countries. Don't forget this is a world wide forum. Not everything needs meet nanny state rules. Just best practice.

BTW where do you imagine the dead short happening that won't be sensed and dealt with by the BMS and or the monitoring Guage shunt?

Great then you are safe. Was claims director at big insurer, worldwide so aware of that countries and rules are different. Due to that i also know the tricks to use to get out of big claims...dirty business, happy i am retired...

A short is never handled by the BMS, always by fuse or breaker.

Most likely that breaker is seen by the surveyor as protecting the main battery cable and i am sure for that its correctly rated.
But what protects the device, in this case the LFP battery itself. There is always a fuse/breaker for the cable that goes to the device and and then another fuse/breaker that protects the device itself. But you can combine this when this fuse is at the device=LFP but then it needs to be up to both specs means interrupt current rating must be below the rating for the cable or device, which is lower. But then it needs also to be up for the max interrupt rating of the LFP, a 120sqmm cable can withstand 30000A for a second but then a fuse must cut this in milliseconds, a breaker won't and melt close.
Do you have drop ins with integrated BMS?
if yes that should have an internal fuse that will take care of this and your fuse has to just protect the cable.
A dead short internally in a cell eg ran dry of lithium, production mistake or by an impact from outside. Or if you use the classic prismatic cells where the casing is positive pole and the heat shrink is rubbed trough......

[newhaul]

Originally Posted by CaptainRivet

Great then you are safe. Was claims director at big insurer, worldwide so aware of that countries and rules are different. Due to that i also know the tricks to use to get out of big claims...dirty business, happy i am retired...

A short is never handled by the BMS, always by fuse or breaker.

Most likely that breaker is seen by the surveyor as protecting the main battery cable and i am sure for that its correctly rated.
But what protects the device, in this case the LFP battery itself. There is always a fuse/breaker for the cable that goes to the device and and then another fuse/breaker that protects the device itself. But you can combine this when this fuse is at the device=LFP but then it needs to be up to both specs means interrupt current rating must be below the rating for the cable or device, which is lower. But then it needs also to be up for the max interrupt rating of the LFP, a 120sqmm cable can withstand 30000A for a second but then a fuse must cut this in milliseconds, a breaker won't and melt close.
Do you have drop ins with integrated BMS?
if yes that should have an internal fuse that will take care of this and your fuse has to just protect the cable.
A dead short internally in a cell eg ran dry of lithium, production mistake or by an impact from outside. Or if you use the classic prismatic cells where the casing is positive pole and the heat shrink is rubbed trough......

Custom build . I don't trust the " drop 8ns" the workings are sealed and not available for inspection
My BMS interrupts any power draw over 300 amps. Period no exceptions and yes I have tested it . Any short that is between the battery and the BMS would have to be at the cell level and your big ( physically big) fuse will do nothing to stop it. Unless you have interconnected cells via fusible links to each cell.
Are you planning to engineer that into the equation?

[newhaul]

Originally Posted by CaptainRivet

.
A dead short internally in a cell eg ran dry of lithium, production mistake or by an impact from outside. Or if you use the classic prismatic cells where the casing is positive pole and the heat shrink is rubbed trough......

Actually my allumum cased prismatic cells from CALB are isolated from both poles .
If not isolated then It would necessitate a sheet of micarta between cells to isolate the from each other. Or as I have a 1/8 inch air gap for heat dissipation

[CaptainRivet]

Originally Posted by newhaul

Custom build . I don't trust the " drop 8ns" the workings are sealed and not available for inspection
My BMS interrupts any power draw over 300 amps. Period no exceptions and yes I have tested it . Any short that is between the battery and the BMS would have to be at the cell level and your big ( physically big) fuse will do nothing to stop it. Unless you have interconnected cells via fusible links to each cell.
Are you planning to engineer that into the equation?

What BMS do you have? And how does it actually cut the power? Most likely a SSR, solid state relay or latching relay and this again will melt close when approached with 20000 or 30000A. Look in the manual of the victron battery protect, its an SSR too and stated there this will happen. This 300A cut of the BMS is meant to protect the LFP from overload but not a fuse/protection for a short.

Yes i don't have fusable link to each cells but with LFP like Lishen thats not needed, its enough if the bank is completely isolated by the junky fuse. The shortend cell is destroyed and will destroy other cells but if you don't draw or charge most likely no fire or damage to installation will happen if fuse/breaker can isolate the bank.
Real problem is that all those low voltage DC fuses and breakers are speced to work with lead, AGM or Gel that limiting the short curcuit current by their own internal resistance. And this works as cable and device protection but not for a 17milliohm device which doesn't limit the current. Thats the real danger of a lithium installation and root cause of a lot of "lithium fires". Its not the LFP that burns but that 20000A sets something else on fire, mostly the cable that then starts a fire.

What in your install is able to interrupt 20000A current if the LFP has a short and delivers that amount of current?
Breaker shown and BMS SSR or latching relay will melt close.

[s/v Jedi]

Originally Posted by CaptainRivet

Wrong AC and DC fuse and Beneteau uses them in all of their new boats from factory.

A fuse has 4 ratings that are important:
Voltage: NH3 up to 690V, better to use the 400V ones as less resistance=less voltage drop
Interrupt current rating: NH3 available in 315 till 690A amps
Acting typ: NH gG or gH is slow acting in overload and fast acting in short curcuit, perfect to protect a LFP as main battery fuse or protect thick wires.
Max interrupt current or interrupt rating (means up to which current the fuse or breaker is able to keep its interrupt function) : NH1-3 120kA AC or 50kA DC
NH fuses are also widely used in public grid eg transformator stations and therefore regularly controlled and certified means you can really trust their spec plus they are cheap.

No, you are wrong:

- Current is in A or kA, not kVa
- Resistance is in Ohms, not W
- the fuses all state AC voltage 40-60Hz

[newhaul]

Originally Posted by CaptainRivet

What BMS do you have? And how does it actually cut the power? Most likely a SSR, solid state relay or latching relay and this again will melt close when approached with 20000 or 30000A. Look in the manual of the victron battery protect, its an SSR too and stated there this will happen. This 300A cut of the BMS is meant to protect the LFP from overload but not a fuse/protection for a short.

Yes i don't have fusable link to each cells but with LFP like Lishen thats not needed, its enough if the bank is completely isolated by the junky fuse. The shortend cell is destroyed and will destroy other cells but if you don't draw or charge most likely no fire or damage to installation will happen if fuse/breaker can isolate the bank.
Real problem is that all those low voltage DC fuses and breakers are speced to work with lead, AGM or Gel that limiting the short curcuit current by their own internal resistance. And this works as cable and device protection but not for a 17milliohm device which doesn't limit the current. Thats the real danger of a lithium installation and root cause of a lot of "lithium fires". Its not the LFP that burns but that 20000A sets something else on fire, mostly the cable that then starts a fire.

What in your install is able to interrupt 20000A current if the LFP has a short and delivers that amount of current?
Breaker shown and BMS SSR or latching relay will melt close.

You do you I do me if you really want to know my complete build setup then come visit my boat I will be happy to show you everything .

Now that being said do you actually have anything constructive to add or just wish to kibitz others on this thread

[CaptainRivet]

Originally Posted by s/v Jedi

No, you are wrong:

- Current is in A or kA, not kVa
- Resistance is in Ohms, not W
- the fuses all state AC voltage 40-60Hz

Incorrect, see eg here:
https://www.ipd.com.au/fuse-link-400...205-m3gg400-69
Go down and click on technical specs:
690V AC or 550DC nominal rating but no problem using in 12 or 24V
Rated interrupt current 100kA in AC and 25KA DC not kVA.
Loss in watts is stated at nominal rating AC voltage and rated interrupt current, so you can easily calculate the resistance. Every fuse is a resistor.

All Nh fuses GG and identical old typ GL which are rated AC can be used in DC too but derated. You have to search a bit in the spec sheets or for some even ask like eaton bussmann.
My older spec Siemens NH3 GL 500A have that even printed on the ceramic body, new ones GG not but they are physically identical.
True is they are mainly sold for AC but can be used in DC too.
They are all produced to a german VDE norm, only difference in GL or GG between different brands is the gas they use inside the ceramic body. Eg Cheap ones in NH3 100kA AC or 25kA DC or expensive 120kA AC or 50kA DC.

[CaptainRivet]

Originally Posted by newhaul

You do you I do me if you really want to know my complete build setup then come visit my boat I will be happy to show you everything .

Now that being said do you actually have anything constructive to add or just wish to kibitz others on this thread

Read it again and you will find a lot constructive stuff and purely simple physics.
There are the reasons i mentioned why no serious brand with reliable specs like blue sea offers marine breaker above 150A.

And this fits very well in that thread as CatNewBee and myself are a rare kind here and running installs with serious high amp loads and discover the problems and issues with eg mis/overrated stuff in daily operations while for most of you you will only discover in emergency situations where its too late and that stuff fails on you when you need it to prevent a catastrophe. And everything above real 150A continous is serious stuff and quality equipment thats up to its ratings is a must.

happy to come by and look at it in person,always interested in other LFP installs and always something to learn new. unfortunately your location says puket and i am in the canary islands.

[newhaul]

Originally Posted by CaptainRivet

Read it again and you will find a lot constructive stuff and purely simple physics.
There are the reasons i mentioned why no serious brand with reliable specs like blue sea offers marine breaker above 150A.

And this fits very well in that thread as CatNewBee and myself are a rare kind here and running installs with serious high amp loads and discover the problems and issues with eg mis/overrated stuff in daily operations while for most of you you will only discover in emergency situations where its too late and that stuff fails on you when you need it to prevent a catastrophe. And everything above real 150A continous is serious stuff and quality equipment thats up to its ratings is a must.

happy to come by and look at it in person,always interested in other LFP installs and always something to learn new. unfortunately your location says puket and i am in the canary islands.

I wish I was in Thailand. No it's Puget sound Washington. Google Seattle WA my home floats 20 odd miles west of there by Bremerton Navy yard.

[CatNewBee]

Originally Posted by BetterDays 2020

I have been searching for a 500 amp Marine Rated Circuit Breaker, and can't find one. Who makes them and where can I find one?



Thanks,

Sorry, 500A and 400A ANL fuses. Lost in translation. The circuits can be interrupted by the 500A BlueSea ML-RBS, so I used real fuses, not this fancy automatic breakers.