exploded battery

Yes, I know after I read the link my P.S.

 

First, the battery on the laptop is a lithium ion so it does not compare to a lead acid at all.
Second, the most likely cause of a battery explosion is a spark. The most likely source of sparks are loose connections. If the connections are loose or damaged so they produce sparks, an overcurrent protector won't be of any help. A fuse burning may actually cause the explosion rather than prevent it.

 

I've been traveling last week and thought a lot about this event.
The purpose of a battery bank is to get more storage capacity in hours only, not to get more current. In my case the only load is an inverter that can draw no more than 80 Amps from 5 batteries, that is a modest 16 Amp from each member, so in a star configuration a simple automotive 25 Amp fuse for each battery could have prevented the explosion.
Some people use a daisy chain configuration to reduce wire length, that -in my opinion- is the wrong choice.

It is unlikely that this happened because of a spark, at least that is not what initiated it.
The picture shows one completely destructed and dried out cell, where hydrogen and oxygen gases were formed before the inevitable spark blew the roof away.

 

Spark is inevitable when a short circuited battery eventually dries out.. That's of course IMO

 

The 777 batteries were an issue from the beginning, they were being replaced well before their service cycles due to high temp warnings. The cells were being torn apart by magnetic fields induced by high current.
The biggest problem is that Li batteries create their own O2 in a thermal run away, you must try to cool the battery, but cannot use water.
The "fix" was to put heavy glass plates between each cell for thermal and current issues.
The rest of the airliners use NiCad, still bad in a runaway but a proven technology and more robust.

 

I think the same goes for the Tesla that is on top of the post.

 

they may be different, but the issue is the same: anything that stores energy can be dangerous. The higher the density energy storage device, the larger potential for an explosion.

Liquid fuel can explode if not handled properly, batteries can ignite or suffer run away reactions, even a flywheel energy storage device can come apart and release all its energy in a massive wreck. some have proven more reliable than others, and eventually they may discover ways to make Li batteries more stable, but even the old reliable lead acid battery can explode if not treated carefully.

 

So how physically would you put the fuses into the system? Where do they go?
We lost 5 1100ah, AGM batteries last year in our house bank. One cell shorted.

We noticed the smell of an overcharged battery, inspected the bank and found 4 of the 5 batteries looking a little pregnant. The charger/inverter had a heat sensor which of course was attached to the battery furthest away from the shorted battery.

This house bank is hooked to the bow thruster and windlass and could draw up to 300 amps prox under certain conditions.

 

The 'best' answer probably depends on your physical layout and if you are assembling a new system or upgrading an old one.

A new system, I would want to wire in a "Star" configuration:
- All the negative terminals to common negative point.
- Each positive terminal through a fuse to the common positive point.

What "should" happen with a shorted cell is that all the OTHER batteries would force current into the failing battery and blow IT's fuse only. And the rest of the system would keep working.

IF you have a tightly-packed row of batteries with short jumpers between them there is no nice solution I can think of. Putting fuses in each of the links in the positive side will protect the other batteries in most cases. But there are many scenarios, none of them very nice unless the farthest battery is the one that fails. AND the fuse ratings?? No happy medium. Grrr...

So investing in enough cable to rewire all the positive connections would be my vote.

What other possibilities are there?

AND, what fuses are available that are not REAL expensive?? And exactly how should we calculate the fuse rating? IsThere any data on how much current a typical Lead-acid battery might draw in the sad scenario Barry told of?

OH. Early Engineering Era. So familiar. More questions than answers at this point.

 

Yes, the current (CCA) are on the label.

 

This is the circuit that I drew but then realized that a fuse between two batteries ( in a two battery bank) could only be as big as half the total amp draw for whatever load that you had downstream of the batteries
Ie if you have two batteries in parallel, had a 300 amp draw, engine start motor, or windlass motor plus all other draws, then you would have to have a 150 amp fuse on each battery to deal with the load (no allowance for spikes)

Then say one battery cell shorted,
This would mean that the shorted cell battery WOULD HAVE AVAILABLE a 150 amp input from the good battery and then this fuse would trip. But the question is that if one cell shorted, would the shorted cell battery draw the 150 amps to trip the breaker or would it say draw 50 amps, which over time would boil the battery dry, or over pressurize the battery
In which case, the fuse would not protect the battery

My thinking on this is that if one cell is shorted, a 12 volt battery becomes a 5 cell battery which fully charged is about 11 volts. So then would a 11 volt battery draw 150 amps from the good battery?
This situation is different than a pure short to ground which would cause an infinite draw, dead short, but rather that one cell is just gone

I considered a diode that would permit current flow to the boats loading. Ie current out to the load but no current able to come back into the battery from the other battery, but then ran into the question. How do you charge the batteries.

Perhaps another charge circuit?

There is a lot of battery information googled on "The Battery University" but I did not find any information about what a battery would draw with one shorted cell.

Gonzo, TK asked is there any data on how much a lead acid battery might draw in the bad situation (one cell shorted) but your answer is what can it put out under the definition of CCA

I will put forth what I understand to be the problem when a cell shorts but welcome any adjustments.

A cell shorts, but this is not a short to ground. You now have 5 cells capable of being fully charged about 10-11 volts. The amperage input from the charging system becomes higher per cell as well seeing a 12 volt input, this creates a higher charge on the cell, hydrogen is created, heat is created, the battery if it has caps open to atmosphere, vents off the water, creates explosive hydrogen, in a closed battery, the vent trips and does the same.

comments

 

Most such problems are typical for paralled banks. Best way to configure big battery banks is to use 2v single cells in series IMHO.

 

That's right Barry, there is insufficient current to blow a large fuse in that case. My battery bank is a different case because the distributed load is much lower, a 25 Amp fuse would be enough.
If you think long enough about this you'll end up with the Tesla solution with current, voltage and temperature monitoring by microcomputers....

 

Could this be incorporated, by adding some sensors + programing, in the 'Distributed Power Systems' that the posts #14 & #15 are about . . ? ?

 

I think your right about that dried up cell. If the cell had exposed plates and they short and the battery is gassing from a high voltage charge then I could see an internal explosion could occur. Otherwise it will take an external spark outside the battery case. So then this could be an unfortunate rare result of poor maintenance, keep water in the battery above the plates. I have never had a battery explode and don't know of anyone that has.