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Old 05-19-2016, 09:03 PM   #21
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the problem is that a quick guess yields the shorted cell drain of a bad battery in parallel with a good battery might be in the range of 160 amps. If that is much more than your loads then it might work.
The fuse is there to protect the wire. Use the appropriate table to find the fuse that keep the cable from igniting. If the batteries catch fire, you are still toast, but a fuse. An keep the wiring from catching fire.
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Old 05-20-2016, 04:30 AM   #22
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I think terminal fuses are a great idea! Very large battery banks have the potential to turn a small problem into a large one. Fuses should definitely be sized to protect cabling but there is no reason they have to be grossly more than the anticipated load. Same goes for terminal fuses. Give a margin to avoid nuisance trips but immediate stop if a bad battery causes the whole bank to discharge into it.

I surveyed a trawler with a Cummins 480C. Its owner had installed a 350 amp fuse on his engine battery bank. Cranked his engine no problem and gave him peace of mind a short wouldn't result in a problem. Made good sense what he did.

Seems that energy storage capacity is the objective not maximum output. Sizing fuses to protect against intra-system faults is a good plan that should be possible without causing issues with day to day use.

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This is what I was thinking as well. We already have fuses at the battery bank to protect the wiring from the battery. There are some pretty simple ways of adding fuses at each battery to protect the interconnect cables. If you have the head room over the battery terminals, just use a terminal fuse.

Reminds me that I need to complete the diagramming of my electrical system.
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Old 05-20-2016, 07:45 AM   #23
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“As soon as I saw smoke from the battery isolator I tried to go back to one or off, but it had fused inside by that time and was rendered useless. "

Good reason to have big bolt cutters nearby to cut big battery cables.

Battery fuses would blow stopping a dead short, the internally shorted battery would get hot but not likely to catch fire.

Odd thing that he switches on both banks, so switch on combining banks then it instantly short circuits. The bad battery suddenly the cell collapses? very odd, never in years have I seen that. I can easily imagine such a devastating short circuit if the polarities of the banks were reversed one to the other, so then joining them with the switch, an instant high current short and fire.

A collapsed cell in a 12 volt battery will instantly bring that battery down to 10 volts. So connecting another 12 battery to the battery with 10 volts will only be a 2 vdc difference, and the current flow would heat up the 10 volt dying battery more than a short piece of battery cable.

How many of you have had a battery fail while connected to a good battery in parallel, and there is not a fire, or a melted battery cable? I have had this several times. The bad battery, the electrolyte can get hot, but where is the fire?

I have never had a battery go into a complete dead short with every cell in a dead short with zero resistance.
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Old 05-20-2016, 08:09 AM   #24
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I have seen dozens of failed batteries in both aviation and marine....all to the point of smoking and sizzling.....but never a fire from just the battery.

But then again...I am sure there have been some.

Just like whale induced sinkings, lightning strikes, deaths from CO from a boat down the docks, bacon grease fires and ugly marine curtains, Ying from heart attacks at sea, etc...etc....

Just can't get into the TF hysteria that every boat is a time bomb, gonna fail because I didn't follow someone else's expert opinion, every new piece of gear makes me safer than using hard won experience, etc....etc....

It's been said many times by better men than I....."it's the bullet you don't see that gets you"....
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Old 05-20-2016, 08:54 AM   #25
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the internally shorted battery would get hot but not likely to catch fire.
I've seen the aftermath of them exploding.

I'm still interested in who has actually put inline fuses between batteries in a bank.
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Old 05-20-2016, 09:50 AM   #26
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I agree with the above that failed batteries seldom explode or catch fire but I have seen several get very hot, emit fumes and vent battery acid.


My intent is not to scare folks but point out that real problems do occur with parallel batteries so folks can be alert to the issue. strange smells and an unusual charging rate are indicators.
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Old 05-20-2016, 10:08 AM   #27
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But even paralleled, I can't recall ever seeing anything more than one battery affected.

Not saying it can't hapoen....but I know more people hit by lightning.
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Old 05-20-2016, 10:12 AM   #28
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Old 05-20-2016, 10:17 AM   #29
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I have seen dozens of failed batteries in both aviation and marine....all to the point of smoking and sizzling.....but never a fire from just the battery.

But then again...I am sure there have been some.
I had a 72 impala that had a battery catch fire. I pulled out of traffic into a new car lot because flames were coming out of the hood. You would not believe how many salesmen came running with a fire extinguisher.

I've also seen a battery catch fire and subsequently detonate on a tow motor in the service.
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Old 05-20-2016, 10:26 AM   #30
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I had a 72 impala that had a battery catch fire. I pulled out of traffic into a new car lot because flames were coming out of the hood. You would not believe how many salesmen came running with a fire extinguisher.

I've also seen a battery catch fire and subsequently detonate on a tow motor in the service.
I said repeatedly that it could happen...but really, how often and why?

Hundreds of millions of batteries in use...and how many and why eventually catch fire?

I know of plenty of other issues that boats have...does everyone scurry around and make their boat perfect in every way?

No...use best practices to a point, keep an eye on things and enjoy with a backup pkan.

If every little thing was required by insurance companies and even common sense...most of us couldn't afford boating or have the boat to a point where we could get underway.

Sure do the simple things that keep us 95 percent safe...that last five percent will drive most people nuts.

For those that don't cruise a bunch or live aboard...do they make the rest of their lives 95 percent safe? Health, home, car, activities...etc...etc...?
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Old 05-20-2016, 05:57 PM   #31
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What psneed said X 2. My remote battery switches simply reflect my evaluation (not necessarily objective - just my latest "Aw crap" vision of what could happen) of possible circumsatances as it applies to my specific boat. Real 90/10 rule stuff with my personal biases and experience added.

Kind of like when I was flying - the most objectively dangerous part of the journey was the drive to the airport.
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Old 05-20-2016, 07:00 PM   #32
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It is not just safety. If you have a bunch of money invested in high tech batteries it makes sense to take some cost effective precautions. If not then don't worry about it.

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What psneed said X 2. My remote battery switches simply reflect my evaluation (not necessarily objective - just my latest "Aw crap" vision of what could happen) of possible circumsatances as it applies to my specific boat. Real 90/10 rule stuff with my personal biases and experience added.

Kind of like when I was flying - the most objectively dangerous part of the journey was the drive to the airport.
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Old 05-20-2016, 07:56 PM   #33
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the interesting thing is his comments about the fire extinguishers. I personally like Purple K extinguishers. They are normally used in commercial kitchens but after seeing a few boats burn to the waterline because regular extinguishers could not stop the fire. The extra cost of the Purple K is worth not having to go swimming (I hope). The boat we just bought has five extinguishers on board but they are only 2.5 lbs each, so each one is worth about a cup of spit. I plan to add at least two ten pound Purple K's and put on within reach of the galley and one near the engine room. Plan for the worst.
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Old 05-20-2016, 11:42 PM   #34
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I am paascared!


Kidding aside - plan to get a couple Big Purple K... for safety sake of any fire happening.
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Old 05-21-2016, 06:39 AM   #35
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I said repeatedly that it could happen...but really, how often and why?

Hundreds of millions of batteries in use...and how many and why eventually catch fire?

I know of plenty of other issues that boats have...does everyone scurry around and make their boat perfect in every way?

No...use best practices to a point, keep an eye on things and enjoy with a backup pkan.

If every little thing was required by insurance companies and even common sense...most of us couldn't afford boating or have the boat to a point where we could get underway.

Sure do the simple things that keep us 95 percent safe...that last five percent will drive most people nuts.

For those that don't cruise a bunch or live aboard...do they make the rest of their lives 95 percent safe? Health, home, car, activities...etc...etc...?
That comment I made about the qty of salemen coming to the rescue with extinguishers? It was more than just that, burning batteries have a tendency to explode and the thought of battery acid landing on a bunch of new cars gets salesmen running.

Its also more than just the probability of a failure. Just as it's uncommon to have a battery catch fire, it's also uncommon to need to throw a battery switch to prevent a fire, but they are on pretty much every boat I have seen. I'll wager they are on yours too. You have to weight the probability with the cost of a failure.
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Old 05-21-2016, 06:41 AM   #36
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For those that don't cruise a bunch or live aboard...do they make the rest of their lives 95 percent safe? Health, home, car, activities...etc...etc...?
Yes, those things I am in control of. Life is so precious. Having come extremely close to losing mine three times due to circumstances beyond my control, I'd feel like a complete idiot (to myself) for not to address those threats I do control. Some people don't place as high a value on their life, fine; just don't unnecessarily threaten mine as a result.. thanks in advance.
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Old 05-21-2016, 07:12 AM   #37
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I'm wondering how old the batteries were. It would be interesting to see a graph of catastrophic battery failure relative to age. It would be nice to have my battery bank last 5 to 10 years. But if 90% of these type failures were past a certain age, changing at 5 years might make safety sense.

The other item not addressed in the article was boat use. My charter boat bounces around (Small boat and lumpy conditions) a fair amount when running in the ocean. Cell failures are more common after 3 years. The stuff that sluffs off the plate eventually shorts out the plates in one cell. So I run 2 or 3 seasons and sell the batteries. My trawler will hopefully have a more gentle life and greater battery life. Wondering if battery age and boat use played a roll in the battery fire?

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Old 05-21-2016, 07:19 AM   #38
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Could this fire have occurred from one bank being completely drained and switched too a fully charged bank, or would there still have to have been one or more dead cell batteries in that bank?

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Old 05-24-2016, 08:16 AM   #39
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Could this fire have occurred from one bank being completely drained and switched too a fully charged bank, or would there still have to have been one or more dead cell batteries in that bank?

Ted
No, not possible. a discharged battery is just a big resistor, there is internal battery resistance to the charge, it will get hot eventually and vent hydrogen bubbles.

An exploding battery is a a hydrogen explosion, which might be able to catch something on fire, but not wires. Wires burn due to a short circuit, they can get red hot. An internal battery short, the system is wet, not dry. Not much in there to burn except a wet plastic case. The original story talks of wires everywhere in the floor, walls, ceiling and them al burning catching the boat on fire. Well wires do not burn unless the current flow in them vastly exceeds their rating and that happens with a short circuit or extreme load, and that happened after the guy joins the banks together after he had worked on the batteries, fully charging them, so IMO, he did something wrong in the wiring.
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