exploded battery

This battery was part of a 500 Ah battery bank that stores power from a solar panel array.
Charging and discharge currents are less than 10% of the capacity, voltages are monitored. BUT: if a short develops in one cell, the other members in the bank, each with at least 800 A cranking power, deliver enough current to blow the faulty battery to kingdom come.

The lesson: use fuses or fusible links between all batteries in a bank to prevent this from happening!

 

I recently read a claim (not sure where) that such problems don't actually occur. Looks like at least one thing I read was not correct.

 

A dead short in a Pb-SO4 wet cell is always going to get hot and evolve H2 (the heat drives it out of solution). And it doesn't even have to be a short (though the nearest cell looks like one). Any sufficiently high charge/discharge rate will heat the battery and evolve gas. So hot metal+ hydrogen gas + spark = bad things. I've been standing next to a car battery when it went during a hard cranking. Not fun. Even worse when it is a large wet cell, like a submarine battery. They torture cycle test those things in a fireproof bunker, and there are still problems occasionally. Google "lead acid battery explosion" for more pictures.

 

any battery, like liquid fuels, are a means of storing lots of energy. the potential is always there that a fault or defect will cause all that energy to be released all at once, and this is the results. This is not new, but for marketing reasons it has been kept quite.

Who ever says otherwise is either ignorant or a lier. Mishandled liquid fuel has the potential of releasing all of its energy in one big "whoosh" as well, with well known results. Batteries are no different, in fact the higher the energy density of the battery, the more unstable it can be.

The problem with a battery is there is not much you can do about internal defects that have the same potential. All fire departments in the USA (and I am sure elsewhere) are being trained to handle electric and hybrid car batteries, to disable them BEFORE any rescue of passengers can commence because they are too dangerous. So rescue crews have to stand back, even if there are bleeding victims or a raging car fire, until after the "battery crew" (wearing bulky blast suits) uses the jaws of life to rip off the hood, locate the battery pack, and severe the cables. Only than the rest of the first responders can tend to the occupants.

Tesela, Apple and many others who's products depend on high energy density batteries have had a number of run-away reactions in their high tech battery packs, usually severely injuring their users, and completely destroying their product (in several cases lap top computers started cars on fire, destroying them). They have made big out of court settlements to the victims to minimize publicity so the public does not think their lab top or high tech (and expensive) electric car is a public hazard. I would not want that kind of thing to happen in my high tech electric boat.

There is no safety nor economy in using batteries to power a car or boat. all you are doing is transferring the burning of fuel, to make the electricity, from your engine to a remote power plant so you can charge your batteries. Properly handled liquid fuel is safer, lighter and more compact than an all electic boat or automobile, and you get much longer range as well.

 

cdk

thank you

 

Thanks CDK

Wow . . .

- - click pic for source - -​

Wouldn't have liked to be in this Corvette either . .

 

Whoever told you that was either stupid or hopelessly misinformed. Batteries can explode, catch fire, melt down, and other disasters all involving heat from multiple sources. Overcharging, thermal runaway, outgassing and a spark (spark from a nearby source) I have seen many many occurrences through out my years in Boating Safety. Lithium batteries are famous for this, but it can occur in others, even supposedly sealed batteries.

 

Professional BoatBuilder #152 Dec 2014/Jan 2015 had an article on Common Systems-Installation Errors by Ed Sherman of ABYC with several photos of batteries wired in parallel without apparent overcurrent protection between the batteries. (Sherman is described as "Director of Educational Programming for the American Boat & Yacht Council.")

Peter Rosenfeld in a letter in ProBoat #154 said "In pictures 15s and 15d (pages 64 and 65) of Ed Sherman's article, a common installation practice is shown that I have been led to believe is dangerous: wiring batteries in parallel without overcurrent protection." Rosenfeld follows by saying a short in cell of a battery in parallel can produce a fire or explosion if there is not overcurrent protection between the batteries, and that he always provides overcurrent protection between batteries.

Ed Sherman replied with "Although I may agree that theoretically the scenario Mr. Rosenfeld describes is possible and could cause a problem, there isn't any history to support a genuine need for fusing between batteries at the this point." Sherman continues with "The ABYC only within the last several years instituted a requirement for overcurrent protection at the end of the chain of a paralleled configuration, and installers and boatbuilders are by and large doing that." He then goes on to say that the short-circuit current potential increases with the number of batteries, and that "for larger banks, even though existing standards do not require this as yet, many of us who advise others in such matters suggest that intermediate fusing schemes be applied. For a smaller, two-battery bank, however, I feel the single fuse, typically a class T, is adequate."

 

Indeed.

That's why batteries, on a boat, should always have its own self contain separate box, made from GRP or similar. This is how we do all our boats.

 

The exploded battery in the initial post was reported to be part of a battery bank, apparently with batteries wired in parallel. In that situation an internal short in one battery involving one or two cells lowers the potential across that battery compared to the other batteries in parallel, and very large currents result, particularly through the battery with the short, as noted by CDK, the OP. The un-shorted cells in the battery with short are being charged at a very rapid rate by the other batteries in parallel. Hydrogen is produced at a rapid rate and the battery can become extremely hot. The cables connecting the batteries may also overheat. An explosion may follow. However if each battery has individual overcurrent protection such as a fuse, fusable link or other device which opens and isolates the shorted battery then the battery with the short will be protected and the battery bank will continue to function without the battery with the short.

Batteries in series do not have this problem. The current is the same through all batteries, even if one battery develops an internal short. A single overcurrent protection on batteries in series is presumably sufficient.

Battery explosions also occur without an internal short in a battery in a bank being involved if the hydrogen produced when the battery is charging is not safely vented. Overcurrent protection does not safeguard from explosions in these circumstances.

Back to battery banks with batteries in parallel - what is the rationale for not installing overcurrent protection for each battery?

 

Hi Everyone,

There are lots of things that have been "Done that way" for decades, and "usually work fine"..

But there is physical reality which knows nothing about regulations, conventions, physics or chemistry. It just does what it does.

The photo of the battery and some reflection about what is known about batteries makes the unlimited-current connection something that we need to do something about.

Almost all the 777 batteries were No Problem. Except the two that were.

CDK has survived to be an Engineer, and retire. My wife sometimes thinks I'm over-cautious. But I've lived to be an Engineer who has been retired for 20 years

 

That is why there are regulations and standards. Most boats are built fine, except those that aren't.

Most battery installations on boats are fine, except those that aren't.

 

search for battery fire turns up quite a lot:

 

Yachting Monthly has an article about digital power distribution, I didn't buy the magazine (€ 8.50 on paper here, a bit too much I think) so I don't know what it is about or if it helps to prevent batteries from exploding.

It's in the June 2015 issue, of which I saw the paper version already in the bookstore on May 9, 2015 . .

P.S. - Just saw Yachting Magazine has an article online about it.

 

That it si about Distributed Power systems. See Yachting Magazine http://www.yachtingmagazine.com/distributed-power-systems?page=0,1 and Panbo http://www.panbo.com/archives/2010/04/bep_czone_1_distributed_power.html

Nigel Calder did a series of articles about it in Professional Boat Builder a few years ago.

It is not the solution to battery explosion issues.