Keeping the water off your Lifepo4 installation

[CaptainRivet]

Originally Posted by CharlieJ

@Jedi:
That is what I surmised.

I am perplexed by his stand on OCPD placement.


Since all the OCPD's that I am familiar with respond to an overcurrent event downstream from their installation position, an internal bank short circuit, upstream from the "battery fuse" will not cause the "battery fuse" to open. Or am I just missing something?

sure it will blow the fuse, power is like water take the path with less resistance doesn't matter if up- or downstream especially if you are talking about >10000A even tiny air gaps is like a solid wire.

as I said i even had that once over 20 years ago arcing the class T fuse with an Lithium bank.
a lead with its high internal resistance limits itself in current in a dead short internally thats why you don't need a battery fuse.
The 0,12mv internal resistance is basically already very close to a dead short and nothing is limiting current, thats why you reach in a 1120AH bank 16500A max. Thats why you need to fuse upstream too with lithium.
And well does it hurt to put a big fuse that also can act as disconnection switch additionaly as first to battery, definitly no.

[CaptainRivet]

Originally Posted by s/v Jedi

I guess he means arcing. Still, the class-T fuse is the correct one to use exactly because it has a better rating but he doesn’t get it.

correct arching
class T can be used in lithium house with bank size that doesn't create more then 5000A short curcuit, you can calculate how much that is. above that only NH.

NH fuses you can also get in fast acting, not only slow. But I use on purpose slow as its fast acting in a dead short but tolerant to short periodes over to run inductive or inrushing loads from motors.
And NH have the better spec then class-T for big house batteries. there is a reason NH are trusted to protect hospitals and our houses while class T is used in electronics especially due to there small size and very fast acting charateristics to protect very current sensitive components. a lithium doesn't contain such very current sensitive components. at dead short conditions they acting the nearly the same way, just class T cannot handle the arching which NH can. Additionally NH has a lower internal resistance =voltage drop running at full rated spec then class-T, again the big ceramic body offers much more cooling so its not transfered in the cabling and busbars. There are designed that way as voltage drop is wasted energy in grid and in factories as that uses enormous anount of energy that saves several thousand bucks a month. fuses are after the meter, so you pay for there drop and waste.

[donradcliffe]

When I did accident analysis for nuclear power reactors, we designed to what was called a Maximum Credible Accident. The NRC agreed with the MCA concept. If we didn't establish a rational boundary, the "what if " questions would have meant that the reactors could never be built.

[s/v Jedi]

Originally Posted by CaptainRivet

correct arching
class T can be used in lithium house with bank size that doesn't create more then 5000A short curcuit, you can calculate how much that is. above that only NH.

NH fuses you can also get in fast acting, not only slow. But I use on purpose slow as its fast acting in a dead short but tolerant to short periodes over to run inductive or inrushing loads from motors.
And NH have the better spec then class-T for big house batteries. there is a reason NH are trusted to protect hospitals and our houses while class T is used in electronics especially due to there small size and very fast acting charateristics to protect very current sensitive components. a lithium doesn't contain such very current sensitive components. at dead short conditions they acting the nearly the same way, just class T cannot handle the arching which NH can. Additionally NH has a lower internal resistance =voltage drop running at full rated spec then class-T, again the big ceramic body offers much more cooling so its not transfered in the cabling and busbars. There are designed that way as voltage drop is wasted energy in grid and in factories as that uses enormous anount of energy that saves several thousand bucks a month. fuses are after the meter, so you pay for there drop and waste.

You are wrong, class-T fuses have a 20kA rating. If you insist on 5kA then you must provide citations to support that. Here is mine, 20kA:

[newhaul]

Originally Posted by donradcliffe

When I did accident analysis for nuclear power reactors, we designed to what was called a Maximum Credible Accident. The NRC agreed with the MCA concept. If we didn't establish a rational boundary, the "what if " questions would have meant that the reactors could never be built.

So it was you I was Navy 4956 welder

[CaptainRivet]

Originally Posted by donradcliffe

When I did accident analysis for nuclear power reactors, we designed to what was called a Maximum Credible Accident. The NRC agreed with the MCA concept. If we didn't establish a rational boundary, the "what if " questions would have meant that the reactors could never be built.

Thats called six sigma, i am a certified blackbelt and posses the certificate of execellence means i completed serveral high scale multimillion dollar projects successfully :-) so i know a bit of that.
I doubt you can protect surroundings from radition caused by a melt down of your nuclear plant with 50Euro.
In a melt down of a lithium bank you can :-)
And in a boat a highly likely catastrophe scenario is a shortend bank by water ingress. Then you rate the factors to reduce the risks by effectivity, cost and resource impact. And a 50 or even 150Euro battery fuse is very economic, high effiency to reduce risk, fast implemented so very high up to be done and not . Used as seperation switch too you don't have even extra costs, switch costs the same but has only 1 purpose...

@yedi: not everybody has an offshore sailing tank like yours with couple watertide bulkheads and isolated bilges. i would actually bet 60-80% of production boats have non at all.

[s/v Jedi]

Originally Posted by CaptainRivet

Thats called six sigma, i am a certified blackbelt and posses the certificate of execellence means i completed serveral high scale multimillion dollar projects successfully :-) so i know a bit of that.
I doubt you can protect surroundings from radition caused by a melt down of your nuclear plant with 50Euro.
In a melt down of a lithium bank you can :-)
And in a boat a highly likely catastrophe scenario is a shortend bank by water ingress. Then you rate the factors to reduce the risks by effectivity, cost and resource impact. And a 50 or even 150Euro battery fuse is very economic, high effiency to reduce risk, fast implemented so very high up to be done and not . Used as seperation switch too you don't have even extra costs, switch costs the same but has only 1 purpose...

@yedi: not everybody has an offshore sailing tank like yours with couple watertide bulkheads and isolated bilges. i would actually bet 60-80% of production boats have non at all.

Are you an AI? It’s obvious you’re not chatGPT but I’ve met a range of other ones online incl. some at this forum…

[AKA-None]

Originally Posted by s/v Jedi

Are you an AI? It’s obvious you’re not chatGPT but I’ve met a range of other ones online incl. some at this forum…

At least coherent

[CharlieJ]

@CaptainRivet #46:

sure it will blow the fuse, power is like water take the path with less resistance doesn't matter if up- or downstream especially if you are talking about >10000A even tiny air gaps is like a solid wire.

How can an upstream short circuit internal to the battery cause a downstream OCPD to open? Please provide a sketch that shows the circuit. Feel free to analyze using Kirchoff's Laws.

BTW, electrical current does not only take the path of least resistance back to its source, it takes all paths back to the source with the resistance of each path determining the amount of current flowing through that path.

[Fuss]

So I ended up making the new lithium installation fit inside the original battery box. That means both lithium 24v batteries and all fuses, switches and bus bars. The fuses, switches and bus bars and shunts are on a quick release panel Incase I want to remove the batteries. I then made a wooden lid with shortish sides that fit over the top of the battery box so that water from the top would have more difficulty getting inside.