Fuse Fire

chrisski

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So with a 25 amp fuse, this is the chart off the blue sea website for a ATC/ATO fuse:

1626914345759.png
So, with a 25 amp fuse running at 27 amps, that would be at or just below the trip area, so I wonder if it found the sweet spot where it was very hot, but not at the spot where it would melt and stop the current.

Probably was more to do with corrosion.
 

mitiempo

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Attached are the pictures showing the fuse before it burned up. This is also before I replaced the batteries. The new batteries only had the single threaded post so I had to move the one wire in this picture that was on the other post to the stud with all of the others. Is there any issues with all of the wires going to the 1 stud? I would like to find a better copper plate to spread out the connections.
There should be a minimum number of wires on a battery. Other than any cables linking batteries in either series or parallel there should be only one positive and one negative wire on a battery or battery bank - plus a temp sensor if there is one. The main positive and negative should go to buses near the battery and from there solar, shore power charger, alternator B+, etc are connected with appropriate fusing.
 

Lee R

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Yes they have the battery terminals very busy in the set up. The buses sound like a good plan to clean it. That is on my list.
 

ken morgan

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There should be a minimum number of wires on a battery. Other than any cables linking batteries in either series or parallel there should be only one positive and one negative wire on a battery or battery bank - plus a temp sensor if there is one. The main positive and negative should go to buses near the battery and from there solar, shore power charger, alternator B+, etc are connected with appropriate fusing.
so how do you figure in BMS's and or active balancers? IE: there are no absolutes in life...even my statement denying them.
 

mitiempo

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so how do you figure in BMS's and or active balancers? IE: there are no absolutes in life...even my statement denying them.
My post was aimed at the original poster with Fla batteries.

Sense wires, whether for a BMS or temp sensors definitely have to be on the posts if the technology calls for it. BMS wires are typically tiny and act as their own fuses.
 

Texas-Mark

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I did not read every reply, but saw several people talking about poor connections. A poor connection will not cause a fuse to glow. A poor connection can cause the actual connection to get hot (and maybe glow) due to the build up of resistance, but is not going to cause more current to magically flow though a fuse and make it glow.
 

Bob B

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I did not read every reply, but saw several people talking about poor connections. A poor connection will not cause a fuse to glow. A poor connection can cause the actual connection to get hot (and maybe glow) due to the build up of resistance, but is not going to cause more current to magically flow though a fuse and make it glow.
If the bad connection were on the spade of the fuse it sure could.
 

Texas-Mark

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If the bad connection were on the spade of the fuse it sure could.

Like, I said, the poor connection it's self could, but not likely the whole fuse unless it is just from heat transfer. My point was that poor connections do not increase current flow through other devices (like fuses), If anything, they reduce current flow (through those other devices).
 

Hedges

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What the poor connection can do is elevate temperature, so fuse or breaker trips at a lower current.
We expect a fuse to go into thermal runaway, so having it sit there glowing seems unlikely.

(Not impossible, if we try hard enough to design a circuit keeping the fuse at an unstable equilibrium. But for any expected load, hotter fuse should increase in resistance and dissipate even more power, racing to the point of burning out.)
 

Texas-Mark

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What the poor connection can do is elevate temperature, so fuse or breaker trips at a lower current.
Yes, this is true. This is assuming the fuse or breaker is near the point where the poor connection is and the heat is generated. All too often I hear people blame a blown fuse on a bad connection 3 feet away. They seem to think that the bad connection somehow increases the current flow through the protection device.
 

Hedges

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Which it can in some cases, especially a motor that fails to start.
For switching power supplies, dropped voltage raises current draw in proportion, so if severe enough this might happen. In which case they may have been saved from a fire by the grace of fuse.

In each case, have to consider the loads, rating and type of fuse to figure it out.
I've had a breaker trip on my central A/C; maybe a brief power interruption?. Once on my VFD powered pool pump (original 15A had tripped after installing 3-phase and VFD so I changed to 20A.) But it tripped once recently, I assume something transient but not sure what.
 

Bob B

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They seem to think that the bad connection somehow increases the current flow through the protection device.
Where did anyone except you say that a bad connection increased current flow?

I can think of some circumstances where that would happen ..... some devices want a certain amount of POWER. If you cause a voltage drop .... they will require more current to get that power.
I don't, however, think that applies to this case.
 

Texas-Mark

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Where did anyone except you say that a bad connection increased current flow?
I never said that. I said I heard people say it (that it can cause a fuse to blow). I also saw people here immediately blaming a poor connection for the fuse "glowing".
 
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Texas-Mark

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I can think of some circumstances where that would happen ..... some devices want a certain amount of POWER. If you cause a voltage drop .... they will require more current to get that power.
I don't, however, think that applies to this case.

You might find that in an AC circuit where maybe a bad connection somehow causes a locked rotor condition (like in a compressor) and then might draw more current. But in DC circuits like this, more resistance somewhere typically results in less current.
 

Bob B

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I never said that. I said I heard people say it. I also saw people here immediately blaming a poor connection for the fuse "glowing".
I have seen things glow red hot because of a bad connection .... and seen bad connections get hot enough to cause fires in electronic equipment.
Maybe your perspective is just too limited.
 

Bob B

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You might find that in an AC circuit where maybe a bad connection somehow causes a locked rotor condition (like in a compressor) and then might draw more current. But in DC circuits like this, more resistance somewhere typically results in less current.
Didn't I say I didn't think it applied to this circumstance?
 

Texas-Mark

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I have seen things glow red hot because of a bad connection .... and seen bad connections get hot enough to cause fires in electronic equipment.
Maybe your perspective is just too limited.

You don't seem to be reading what I wrote. I clearly said a bad connection "could" glow. What I said is that a fuse not in close proximity won't unless it is from transferred heat.
My perspective is having an electrical engineering degree. But this is Ohm's law 101.

I know I am the new guy around here, but I have been doing electrical for over 40 years. I certainly do not know everything about solar (only been doing that for about 18 years), but current flow is current flow.
 

Bob B

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You don't seem to be reading what I wrote. I clearly said a bad connection "could" glow. What I said is that a fuse not in close proximity won't unless it is from transferred heat.
My perspective is having an electrical engineering degree. But this is Ohm's law 101.

I know I am the new guy around here, but I have been doing electrical for over 40 years. I certainly do not know everything about solar (only been doing that for about 18 years), but current flow is current flow.
But .... You are ignoring the fact that the spade connection on the fuse is a mechanical connection and is .... part of the fuse body. A bad connection on that spade could easily get hot enough to glow and melt down that fuse holder.
Not trying to say that absolutely was the cause, but you seem to be determined to say it isn't a possibility at all. I have seen similar things happen many many times.
.... and you are trying to belittle anyone who could possibly think that could happen.
 

mrzed001

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Where did anyone except you say that a bad connection increased current flow?

I can think of some circumstances where that would happen ..... some devices want a certain amount of POWER. If you cause a voltage drop .... they will require more current to get that power.
I don't, however, think that applies to this case.

Bad connections increase resistance, so increase Voltage drop and heat production.
P = I^2 x R (W = A^2 x Ohm)
Bigger resistance, more heat. Also resistance grows with heat (producing more heat that more resistance ... ).
We use this in the (melting) fuses.

Also a page from a product like this fuse holder :
https://www.redarc.com.au/faq-tech-tips/bad-fuses-or-bad-fuse-holders
 
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