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Posted: Fri Dec 01, 2006 5:35 am
Modern 'maintenance free' wet cell batteries can be a time bomb!
Over the past year I've seen several batteries explode with no obvious reason, but, closer investigation does indeed show what happens. As is well known, charging a wet cell battery causes an electrolyte loss as hydrogen and oxygen gas is created as byproducts. Normally these gases dissipate into the air and the concentrations are too low to be a hazard. Yes, we've all been taught and warned about sparks and hooking up jumper cables around these batteries for this reason, but that is not the issue here!
In a maintenance free battery, since it is difficult or impossible to check the electrolyte level, the battery is manufactured with adequate electrolyte fluid to last the â€˜expected lifeâ€™ of the battery.
So far, there are no issues of concern, but here's where it all goes sour
Sometimes these batteries are placed in service differently then the manufacturer expected. In many applications they are left on charge with infrequent energy demands. A lawn tractor connected to a trickle charger, and battery powered materials handling equipment, used infrequently but charged every night are examples. Because these batteries are often oversized for the application, they provide useful power for a much longer lifetime than expected. No free lunch here! The down side is that the battery ages poorly and runs too low on the factory filled electrolyte.
Now the plot thickens!
The electrolyte can become so low that the plates begin to be uncovered and there is a large void space inside at the top the battery. Still there is no problem, except diminished capacity, unless there is a defect in the battery. Problems like loose or weakened internal connecting links or crumbling and loose plate debris are common. With age, this is more than a possibility itâ€™s almost a certainty. If the defective link breaks or the debris shorts with a large battery current, like from a boost charge or from a starter motor, it creates a spark. Since this spark occurs in the hydrogen rich space above the plate, which is quite likely, look out. An explosion is imminent.
So what's the answer?
If this battery could have been properly maintained, with adequate electrolyte, the space above the plates would have been filled with electrolyte. The spark could still have occurred but it would be submerged in the electrolyte, which is not explosive, instead of the volatile gas mixture.
Avoid using wet cell batteries that cannot be maintained if it is to be used in long term charging applications. If it is unavoidable to use a maintenance free battery, plan to replace the battery soon after the end of the manufacturerâ€™s warranty period, bad or not. To minimize unnecessary electrolyte loss frequently check the level and consider the use of the battery and charge accordingly. not according to the clock. Sure, there are sophisticated batteries and chargers that are supposed to take these factors into consideration but the truth is, many chargers don't.
The most recent battery explosion I was involved with was a marine deep cycle battery from a well-known maker installed on a powered pallet jack. It was not a bad battery it was just too old! The amount of electrolyte was so low that the plates were damp and crumbling, but not covered with electrolyte. Previously this pallet jack seemed to work just fine with 'plenty of juice'. Because a battery can provide power it may not be a 'good' battery. The end of battery life is the end of battery life, one way or another.
Posted: Fri Dec 01, 2006 6:12 am
i have a few lead acid deep cycle batterys that were used in a powered wheel chair,,they are working find but it seems the sides are sucking inward,,like its creating a vacuume, (they look malnurished
is this something to be concerned about?
also can batterys be going bad if they are stored,even tho they still hold a good charge?
and last but least. some sealed batterys i have are working fine, but i noticed the amp meter kinda jumps a little ,just before the batterys fully charged.. is this something to be of concern too ?
Posted: Fri Dec 01, 2006 8:09 am
Are the batteries getting hot during charge? If so there is definately a problem. Are they servicable, with caps or plugs, if not they may be dry and overheating! Normally, the battery cannot create a vacuum since there are vents for the gas.
As for the storage, well that depends on the conditions. Too cold/hot both have bad effects but a battery should always be fully charged before storage and periodically afterwards, perhaps once a year. (Nope you don't need to put them on a wooden plank either!)
Meter wiggle: If the meter dances slowly, I might suspect that the charger has a fault, or it is a cheap charger. If the meter suddenly drops off then comes back up, suspect a defective battery and consider replacement. A battery can do strange things when it gets older and that might be a sign of some plate deterioration.
For a quick charger test, hook some 12 V lights, like a headlight, up to the charger to draw a typical charging current to see if the meter wiggles.
Hope this helps...
Posted: Fri Dec 01, 2006 8:18 am
Simple cure, hermetically seal them in two layers of plastic bags, [or a box] hydrogen with out oxygen cant explode.
Old as the hills.
Posted: Fri Dec 01, 2006 1:58 pm
lenp >> no the batterys are not getting hot, and they are stored indoors..and the needle does not jump with all the batterys that i charge..this charger is one of them smart chargers they use on wheel chairs, it charges to a point, then switched to trickle charge.
but sometimes while its charging the needle gets nervous almost before its fully charged. but with other batterys it will be stable..
the batterys that cause the needle to get nervous or jittery, seem to be working fine tho...
also the battery that is sucking inwards ( vacuumed ) the maintence caps are non servicable.. i hear they have vents that let gas vent,,but i do not know if it lets then bringback in fresh air..its as if they are 1 way valves, and the battery hasn't been used much.. mostly stored,
when i charge it,, its indicates its still got 90% charge, and will only charge for a few min, before its full again.. this is a 80AH battery BTW.
i guess if it works, then let it be...
Posted: Fri Dec 01, 2006 4:24 pm
Regarding the plastic bag idea, well I don't think it would work.
When you electrolyze water you get both hydrogen and oxygen.
Check out http://en.wikipedia.org/wiki/Electrolysis_of_water
for the details.
If the atmospheric O2 was the problem how would it get into the top of the battery to mix with the hydrogen to cause the bang since the gas pressure is being vented, under a slight pressure to the atmosphere. I really think a plastic bag would make a BIGGER BANG!
Posted: Fri Dec 01, 2006 7:18 pm
You can fight history all you like, it works and its old news.
Take it from the elders.
Then,...Take up chemistry next?
In chemistry there is the first rule of thumb for all â€œrapid oxidationâ€
Posted: Fri Dec 01, 2006 8:47 pm
What 'history' am I accused of fighting? Where are the bags for batteries sold? Are they supplied with the batteries? In our society if a battery were to explode and someone were injured because the manufacturer did not supply, or suggest that the battery be in a bag, the lawsuit would buy all the bags for all the batteries for years!
There's also a common misconception about putting a battery on a piece of wood to keep it from discharging but I will not go there!
What you might have missed is that this is an explosion inside, not outside, of the battery.
Now, as for the elders remark, watch your step since you don't know my age!
And just as a note, did you bother going to the site I mentioned?
(By the way, this 'old news' could not be found in the Google world)
I'm not interested in a contest of our literary ability and probably will not debate this because I refuse to throw away the facts to let the theory survive.
Who wants to bag their battery instead of proper application and maintenance?
Posted: Fri Dec 01, 2006 10:29 pm
Let me explain my ancient formal training, ....Physics, electronics, mechanical engineering. [and degrees since the 70s]
First in physics and mechanical engineering, no explosion can occur with out the proper ratio of the fuel to Oxygen. NONE.
A bad mix will not detonate.
[inside or out must occur with a proper MIX, and a plastic seal screws this up]
With gas you need 14 pounds of Air to one pound of gas.
More or less of either is a complete DUD.
No battery reaction will supply the correct amount of oxygen or hydrogen to go bang.
Any bag around the battery will starve off the proper mixture of air, hence no explosion will occur.
[See marine environments and their fiberglass boxes that protect]
Second is the myth that a battery wonâ€™t discharge on a cold surface.
These wives tales comes from short trials, not mentioned in the fact that cold [concrete] does draw down and alter the acid level, and thus the battery if you leave it "long enough".
No body waits to see.
And if you feel lucky, toss a match into a FULL can of gas, no bang, just a small harmless flame.
Do it empty and see the pearly gates.
And age, no, just degrees and lots wisdom.
Wives tales still exist, and are boooooring....
Try engineering, physics, and science, it cuts through the normal bull.
Posted: Fri Dec 01, 2006 11:44 pm
Posted: Sat Dec 02, 2006 7:05 am
I really hate to do this but here it goes:
First, There is enough chest pounding about your accomplishments! I don't need to expound on the papers I may have collected, or the subjects I may have mastered. I Just address these issues with facts. You, however, have not supplied one fact to support your position!
Do the research and drop the self gratifying theory, and don't talk anymore about gas mixtures. I know all about the LEL and UEL of gasses.
If the bag theory were correct, why don't they manufacture totally sealed batteries, with more space at the top of the battery for the gas to accumulate? Answer: the battery would rupture, as will your bag! When the bag balloons, it will leak and we are still back to escaping gas. I will agree that baging the battery MAY prevent an explosion from an EXTERNAL IGNITION SOURCE but would have no effect for an internal one, except that now we have more gas to go bang.
Supply any references that recommend charging a battery in a 'sealed environment'. I would like to see just one manufacturer, or credible reference, recommend this! Theory that does not evolve into practice is nearly useless.
Why are all secondary batteries vented ? Because they are expected to outgass during the charge and discharge cycle. The newer designs are VRLA (Valve Regulated Lead Acid) vent schemes that require a small pressure to operate the valve. Bagging it negates this engineering concept.
The fiberglass boat battery enclosures are not hermetically sealed, but they are water-proof! Ever see an IP-xx or an NEMA hazard rating on one!
(By the way, battery acid and salt water are a BAD mix, go look it up!)
I encourage you to read the following excerpts, which deal with explosions inside the battery and caution about operating ANY rechargable battery in a sealed environment.
Since I deal with facts, not conjecture, the references are also included.
Mere chest pounding will not be responded to.
......The most probable cause of internal battery explosions are from a combination of low electrolyte levels below the plates in the battery, a low resistance bridge is formed between or across the top of the plates, and a build up of hydrogen gas in the cell. The low resistive bridge is called "treeing" between the positive and negative plates. When current flows in the battery, a spark occurs and ignites the residual gas in one or more of the cells. A second possible cause is a manufacturing defect in the weld of one of the plate connecting straps causing a spark igniting the residual gas. Another source of internal battery explosions are caused from direct electrical shorts across the battery's terminals. The battery rapidly over heats form the high current and can explode. The largest number of internal battery explosions occur in hot climates due to the loss of water while starting the engine. Most internal battery explosions could have been prevented if the plates were always covered with electrolyte. Please see Section 3 for more information on preventive maintenance.
A less common form of internal battery explosion occurs when a dead short is applied across the battery terminals or the battery is in a fire.
......Gassing in open or flooded lead acid batteries.
Theoretically, Hydrogen is only caused by an over-load current. So long as a rechargeable battery is close to full charged, the fed-in current (i.e., the charging current) will be converted into electrochemical energy. In fact, however, certain quantities of hydrogen and oxygen are generated in a rechargeable battery at any time, and that means both when charging and discharging - even when inoperative!
Even when the so-called water decomposition voltage of 1.55 V per cell has not been reached (e.g., in open nickel-cadmium batteries) a certain amount of hydrogen and oxygen is nevertheless released. For this reason it is strictly forbidden to locate any kind of rechargeable battery whatsoever - even gastight nickel-cadmium batteries - in hermetically sealed spaces. Potting them in resin is likewise strictly forbidden.
......Because there is a chance of off-gassing hydrogen and oxygen if the battery is overcharged, it is important to provide adequate air circulation. ( Never charge or discharge a battery in a hermetically sealed enclosure.)
Posted: Sat Dec 02, 2006 10:15 am
Sorry but your off the mark, only a ideal mixture can cause any explosion.
If you alter this in any way you reduce the danger factor by decades, period.
First things first, there is no banging on the chest, just righting the old wives tales daily.
Sorry my research is as old as my degrees which means I donâ€™t need to revisit the wives tales, just explain the real facts.
Bags and batteries? Your lucky to get glue to seal a battery out of these cold corporate stones, especially if it costs a penny.
Second is the fact that hydrogen is highly corrosive along the other out gassing, and this can eat the terminals as shown in any sealed battery environment, hence the maintenance is higher to naturalize it with coatings, grease and physical maintenance to keep it clean.
But for the bang or explosion, there is none in a sealed environment and no chance either if its sealed, hence the safety factor attached to this method.
A bag is the poor mans sealed fiberglass box. Boats and dangerous situations dont expose the out gassing, to the out side environment, except on occasion for a danger pressure blow out device. [One time valve often installed to stop the box from excess pressure build up and damage]
Bags donâ€™t rupture, however in hot situations they leak OUTWARD and not back in to replace the missing gas with air, again keeping the level at an UNBALANCE and thus no explosion.
All the internal sparks in the world wont ignite a bad mixture with any thing but a dud.
No dangerous flames, no explosions with out the proper mixture. [1st year science, mechanics, physics] NONE
You can look up all you like, my experience with batteries, boats, and other dangerous situations goes all the way back to the 70s. I have no need to RE learn what I was taught.
Explosions only occur if the ratio is correct, period. You donâ€™t pass the test or get your degree unless you state these correct facts on the finals. And there is reasons to know why itâ€™s a fact in order for you to be able to diagnosis, find, or fix a situation. Its as simple as that.
Venting is the easiest, cheapest, and most reliable way to deal with this gas because most times there is no problem, no spark, or any source of a flame. But as you know, that not perfect but it is cheap.
You cant be water proof, and not sealed.
The seal is not designed to be a valve, even if it lets out excess or dangerous gas pressure it wont suck in the air out side because this is limited to 14.7 pounds, while the gas build up in extreme conditions my exceed this opposite.
The seal will not leak with a mere 14.7 pounds out side while the inside pressure is lower.
A check valve may be installed but all of these out gassing station donâ€™t DRAW air to make the mixture correct for an explosion. They do the opposite to maintain a off balance of mixture by simple snuffing means from the air contact.
The reasons being how a gas is formed are numerous, however there is only two factors that make it dangerous.
First is the â€œcorrect mixtureâ€
Posted: Sat Dec 02, 2006 2:49 pm
len, silence is the best response here.
by the way, everything I've heard says the best solution for that problem is good ventilation.
Posted: Sat Dec 02, 2006 4:17 pm
Good ventillation is the best and cheapest way to keep the mixture out of ballance, and thus safe from explosion.
I set off "hydrogen with out air" all the time and all it does is pucker.
Bloop,... as it tries to burn and mix at the same time.
Only when you contain and mix the ratio perfectly does it become dangerous. Bang
Try the old gas drop and a long pipe at 45 degrees.
Place a candle at the bottom, drop one drop at the top, and wait for it to mix and drop to the candle.
KA BOOM, WHEN and IF its just right.
Poof or nothing if its too lean or rich.
Posted: Sat Dec 02, 2006 9:43 pm
You've said more than a mouthful and I do think that you've been into the mixture a bit! Now, THIS is the end of this thread...
PS: Thanks Philba!