BU-804a: Corrosion, Shedding and Internal Short

Find out what the user can do to reduce battery corrosion and shedding.

Corrosion occurs primarily on the grid, and it is known as a “softening and shedding” of the lead off the plates. This reaction cannot be avoided because the electrodes in a lead acid environment are always reactive. Lead shedding is a natural phenomenon that can be reduced but not eliminated. A battery that reaches the end of life through this failure mode has met or exceeded the anticipated life span. Limiting the depth of discharge, reducing the cycle count, operating at a moderate temperature and controlling overcharge are preventive measures to keep corrosion in check.

To reduce corrosion on long-life batteries, manufacturers keep the specific gravity at a moderate 1.200 level when fully charged, compared to 1.265 and greater for high-performance lead acid batteries. (See BU-903: How to measure State-of-charge)  A lower specific gravity decreases the specific battery energy.

Applying prolonged overcharge is another contributor to grid corrosion. This is especially damaging to sealed lead acid systems. While the flooded lead acid has some resiliency to overcharge, sealed units must operate at the recommended float charge. (See BU-403: Charging Lead Acid)

Chargers with variable float voltages adjust the charge voltage to the prevailing temperature. Reducing the float charge when the ambient temperature reaches 29°C (85°F) and increasing it when colder lowers corrosion. (See BU-410: Charging at High and Low Temperatures.) Most chargers for stationary batteries feature temperature control, but this not common in vehicles. A fully charged starter battery is kept at 14.40V (2.40V/cell) while driving and this can lead to overcharge. The recommended float voltage is 13.60V (2.27V/cell).

As lead acid batteries are being replaced with Li-phosphate (LiFePO), precise charging is paramount. While the automotive charging system provides the correct end-of-charge voltage for LiFePO, Li-ion should receive no further charge when the battery is fully charged. With the LiFePO replacement, this does not happen and the starter battery receives continuous charge while cruising. Although LiFePO is more tolerant to overcharge than cobalt-blended Li-ion, overcharge can shorten the life of the Li-phosphate battery.

To attain maximum surface area, the lead on a starter battery is applied in a sponge-like form. With time and use, chunks of lead fall off and reduce the performance. Figure 1 illustrates the innards of a corroded lead acid battery.

Innards of a corroded lead acid battery

Figure 1: Innards of a corroded lead acid battery.

Grid corrosion is unavoidable because the electrodes in a lead acid environment are always reactive. Lead shedding is a natural phenomenon that can only be slowed and not eliminated.

Source: Journal of Power Sources (2009)

The terminals of a battery can also corrode. This is often visible with the formation of white powder as a result of oxidation between two different metals connecting the poles. Terminal corrosion can eventually lead to an open electrical connection. Changing the connecting terminals to lead, the same material as the battery pole of a starter battery, will solve most corrosion problems.

The lead within a battery is mechanically active. On discharge, the lead sulfate causes the plates to expand, a movement that reverses during charge when the plates contract again. Over time, sulfite crystals form that cause shedding of lead material. The shedding in a starter battery is manageable because the battery does not go through a deep discharge, but this is a larger problem with a deep-cycle battery.

Electrical short is another failure mode, especially with starter batteries in trucks. As the battery sheds its lead to the bottom of the container, a conductive layer forms that gradually fills the allotted space in the sediment trap. In time, the now conductive liquid may reach the plates, creating a shorting effect. The term “short” is a misnomer and elevated self-discharge or soft short would be better terms to describe this condition.

Soft shorts are difficult to detect because the battery functions normally immediately after charge and everything seems fine. In essence, a charge wipes out all evidence of a soft short condition, except perhaps an elevated temperature during charge that may be noticed when touching the battery housing. However, once rested for 6–12 hours, the battery begins to show anomalies such as a lower open circuit voltage and reduced specific gravity.

The measured capacity will also be low because self-discharge has consumed some of the stored energy. According to the 2010 BCI Failure Mode Study, shorted batteries accounted for 18 percent of battery failures, a drop from 31 percent 5 years earlier. Improved manufacturing methods may account for this reduction.

Another form of soft short is mossing. This occurs when the separators and plates are slightly misaligned as a result of poor manufacturing practices and they cause parts of the plates to become naked. Such exposure promotes the formation of conductive crystal moss around the edges, which leads to elevated self-discharge.

Lead drop is another cause of short in which chunks of lead break loose from the welded bars connecting the plates. Unlike a soft short that develops with wear and tear, a lead drop often occurs early in battery life due to a manufacturing defect. This can lead to a serious electrical short with a permanent voltage drop that could result in thermal runaway.

The most radical and serious form of short is a mechanical failure in which the suspended plates become loose and touch each other. This results in a sudden high discharge current that can lead to excessive heat buildup and thermal runaway. Sloppy manufacturing as well as excessive shock and vibration are the most common contributors to this failure.

Last updated 2017-05-09

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Comments (80)

On March 8, 2012 at 3:53pm
Carl wrote:

In a flooded battery, is it possible for a cell to be open? If so, what can cause a open cell?

On March 8, 2012 at 7:45pm
Wayne Robey wrote:

The above statement users often judge non-functioning lead acid batteries simply as being “shorted.” does not apply to long life sealed cylindrical cells such as made by Gates. I have never seen one of these shorted but I have several that suddenly opened.  Of course sulfation over a long time will gradually produce a near open as well.

On March 10, 2012 at 9:28am
Sanjay wrote:

why lead used in battery

On April 8, 2012 at 8:35am
Chris C. wrote:

In response to Carl: many years ago I was building a powerful winch system for a pickup, designed to pull logs out of the bush. It ran on an 8D size battery and worked with with a huge, 130A alternator. It worked well, but it was hard on the components: batteries would only last a couple of years, the 10,000 lb ‘heavy duty’ winch had to be serviced after a year and the pickup needed new springs at the end of the first season. Anyway, we soon realized that our components were undersized for our needs and that there is a good reason skidders are needed for this kind or work wink But I digress…

The first battery we installed failed within a couple of weeks. Soon after installation we noticed the ammeter would fluctuate quite wildly and suspected the alternator, which we upgraded from 100A to 130A as a precaution, but the problem reappeared. Then one morning nothing, 0 volts. So we took the battery back to the dealer, he said “the battery is sulfated, it’s not covered under warranty” and was reluctant to give us a replacement. After we explained it had been connected to a 130A alternator that worked well (I had both an ammeter and a voltmeter installed to monitor the system), he realized we hadn’t abused it and when he tried to charge it there was absolutely no response, like I expected. Since he had actually worked on batteries before (in the old days you used to be able to remove the top), he said “looks like a weld cracked in one of the cells”. In other words, one of the connecting bars made of lead, which are soldered during manufacture to the internal posts each cell possesses, came lose or broke. Result, open circuit and unusable battery.

So there you have it, Carl. If you suddenly have no voltage whatsoever (I haven’t seen the problem since), one of the cell connections is probably cracked or came unsoldered or perhaps even was never properly soldered in the first place. This type of manufacturing defect will show up more if the battery is subject to a lot of shocks and vibration, like in our installation.

On May 6, 2012 at 12:28pm
Blair wrote:

Just got back from an aborted trip, stopped for lunch, back out to start the car and heard a thump, the battery had split open at the top. 4 year old original equipment. Water level was a little low, but not significantly. Had someone bring me a new battery, replaced it and drove back home. Any thoughts on why the battery failed? Was a little concerned about putting a new battery in that there could have been another reason the battery failed, decided to give it a try anyway.

On May 6, 2012 at 11:50pm
Chris C. wrote:

Blair, that sounds like an internal explosion from hydrogen and oxygen accumulation. Overcharging may have be involved. If the battery developed a short or internal crack, high demand may have caused the spark needed for the explosion.

Advice: check the charging system.

On June 20, 2012 at 2:59pm
John mc wrote:

My 4 year and 2 month old OE battery test readings seem odd. The car in that time has 120k. Lights are never left on when parked, gets lots of driving so should be well cahrged. The EN rating is 570. I’m getting a reading of circa 430 ish, once got 390 but can vary. The open circuit voltage rests approx 12.48 ish, it definately never gets to 12.6. Is my battery faulty? using the tester on other batteries always read higher than the rated 570 and voltage 12.7 at least..

One morning i pulled a fuse and done a crank test. Engine cold. It cranked good and fast. I kept it going for a good 15 secs and the speed of the cranking never declined.. What should i do? The readings say bad in comparison to other batteries but when tested under load from cranking it works great.. Could this fail suddenly?

On September 4, 2012 at 2:22am
karim nawaz wrote:

i am a beginer to learn about a lead acid battery, and want to know whether chemical re-actioin starts before applying dc current to charge the battery or it starts on charging.

On September 10, 2012 at 8:29pm
Manuel G. wrote:

Does a battery cadmium based aditive affecs a lead-acid battery? Could this additive make a battery to “explode”?

On September 11, 2012 at 6:52pm
Wayne Robey wrote:

I used a Cd containing additive several times over 20 years ago wit old engine starting batteries. It was supposed to improve performance by reducing sulfation but did not seem to do anything. I don’t see how it could cause explosion.

On October 27, 2012 at 11:30pm
John Fetter wrote:

Cadmium does nothing in a 12V lead-acid battery until the battery is charged up to 15.5 to 16 volts. It plates onto the negatives and in doing so reduces sulfation. Switch the charger on and off at intervals of a couple of hours, over a period of three weeks and your battery becomes as desulfated as it will ever get.
Putting cadmium into a battery CANNOT make it explode. Igniting the hydrogen-oxygen gas mixture that is given off during charging certainly can. Take care to NEVER create sparks near a battery. I have seen scars on someone’s face that were put there when he playfully made the battery spark by putting a piece of metal between the terminals.

On December 2, 2012 at 12:42am
John Fetter wrote:

Ask any acknowledged lead-acid battery expert this question - Assuming a lead-acid battery is correctly maintained, correctly used, why does it wear out?
Answer: The lead-acid system is subject to slow, progressive corrosion of the positive grids when correctly used. It is subject to sulfation when it is persistently undercharged, (incorrectly used).
A lead-acid battery can give between 4 and 25 years service when it regularly receives a small, controlled overcharge. It can fail within 2 years if persistently used below full state of charge.
A large percentage of leisure marine, light aircraft, truck and automobile batteries are operated almost permanently below optimum state of charge, hence become sulfated.
This does not mean lead-acid batteries will naturally become sulfated, as implied by desulfation merchants. They have products to sell, therefore they will say whatever it takes to sell their products
The dividing line between corrosion and sulfation is a knife edge. There is no safe area of operation. The only way to make batteries last is to subject them to regular, mild overcharging.
The corrosion process begins when a lead-acid battery is formed. The lead at the surface of the positive grids is converted into lead dioxide. Lead dioxide passivates the metal surface. After that it takes many years in service for the layer of passivation to very slowly work its way right into the grids and cause them to fail.
Corrosion is necessary. The process of charging “corrodes” lead sulfate of the discharged positive active material into lead dioxide. The lead-acid system cannot work without corrosion. Undercharging causes lead that is exposed to sulfuric acid to be converted into lead sulfate. If there is no “beneficial” corrosion, there will always be “harmful” sulfation..

On December 3, 2012 at 6:48pm
tiger wrote:

i have replace my meter with new four Ni Cd batteries but still the new one also fails and discharge suddenly. what can be the reason, is that possible that there is some issue in battery holder? as someone told me that holder can get corrosion and that also shorten battery life.

On December 3, 2012 at 7:56pm
Wayne Robey wrote:

Relating to John Fetter’s comment, I have some 220 AH Exide golf cart batteries used for 11 years often floated, often slightly discharged, occasional discharged to no more than 20% SOC use around 50 ml water/cell/year (about 100 ml first year). What I noticed is flaking off on the positive internal buses and swelling upward of the case around the positive terminal. I have not seen this on other batteries and it does not seem to correspond to wear out by total AH discharged over their life. I cannot see any sign of sulphation and the fully charged specific gravity indicates there is not much. What could be done to reduce this problem?

On December 3, 2012 at 11:51pm
John Fetter wrote:

tiger - There is a how long is a piece of string element in your question. I am not trying to be disrespectful. It is not possible for someone else to work out from the limited info.

Wayne Robey - What you describe is normal. The internal connector bars are likely made with an alloy that is sufficiently different to the grid alloy, thus attracting extra corrosion to themselves. When the grids in the positive plates become corroded, they increase their volume. When lead metal is turned into lead dioxide, the resulting material takes up more space. The grids of the plates are firmly connected to the top bar that in turn is firmly connected to the positive terminal. The lid is flexible. Hence the terminal gets pushed up. Ignore the stories about sulfation. They are written by people who have something to sell. When people get old, their faces become wrinkled. When batteries get old, they do what your batteries are doing. There is nothing wrong with your batteries.
As a matter of interest, when the total volume of water that is added over the years reaches the same volume of the electrolyte, your batteries will most likely stop working. I commissioned testing on two sets of Trojan golf cart batteries, two sets of Exide and two sets of Deka golf cart batteries years ago. They all expired after using this amount of water. Two-thirds of them lasted between 40 and 60 percent longer because we had given them something to make them last longer. Their water consumption was slower. I was amazed to find the water consumption so predictive.

On December 11, 2012 at 8:00am
econobiker wrote:

John Fetter wrote: “A lead-acid battery can give between 4 and 25 years service when it regularly receives a small, controlled overcharge.”

I can vouch for this fact of battery life.  I had to buy an automobile battery in order to transport a rented car back to an automobile dealer. I kept this battery on a maintenance charger (in series with 2 to 3 smaller motorcycle batteries) for about six years.  I occasionally used it to help start motorcycles with dead batteries but otherwise it was in a cool basement on the charger for the bulk of the time.  After about six years I installed the battery in a small 4 door car which used it another three years before the battery performance began to degrade. 

The funny part was when I went to buy a new battery.  As auto parts store technician removed the old one, he could not believe that the date code showed a nine year old battery! I allowed him to keep thinking that the battery had been in the car for 9 years…

On May 29, 2013 at 2:51pm
Jim Kincheloe wrote:

Great information !!!!!!!!!!!!!

On June 4, 2013 at 8:33am
Bill Wilson wrote:

I’m in the process of recharging 3 wet Interstate batteries that were barely used before laying idle for 4 - 12 years. I’m using an ancient charger with an amp dial and meter,. I start at 2 amps and it’ll drop to 1 then 1/2 amp then stay there for days with the battery warm and bubbling. The 4 year old lawn tractor battery came back to life with two charge/discharge cycles. Some sulfate remains visible one the plates. The 12 year old Honda Goldwing battery was bulged at the ends, heavily sulfated, took an initial charge and showed 12.6 volts. A fair admount of sulfate disappeared. It discharged in a few hours using a m/c turn signal bulb. Am doing the second charge and noticed that a piece of lead shelled off in one cell and two other cells have developed some lumpy stuff between the plates on top. The battery showed 13 volts, showed barely bad when load tested and went back to 12.3 volts after the test.  It’s back on an 1/2 amp charge to see if the lumpy stuff will dissolve. Will the shelled off lead do the same of should I try to fish it out thru the cap hole?
I haven’t bothered with the 9 year old auto battery yet. It’s been sitting in a car outside in NE Texas since new.

On June 5, 2013 at 10:34am
Wayne Robey wrote:

I have had some success and some failure with these neglected batteries. With continuous charge, it is necessary to maintain a slow charge for a long time, sometimes a month. When done, the capacity will be low and self discharge high. Pulse charging is another approach that I have not tried.

On June 5, 2013 at 2:35pm
John Fetter wrote:

Bill Wllson, Wayne Robey - We discussed cadmium in Sep-Oct. Wayne says he tried cadmium but it did not work. I tried it and it did work. I discovered that it is necessary to get the voltage right up to at least 15.5V by slow charging. Don’t try forcing it up. It must rise on its own account with just a few amps. I used a timer to switch the charger on for one hour, and off for one hour, for three weeks.
The cadmium plates onto the negatives during charge, goes back in solution during the idle periods. Each time progressively infiltrating the sufate. Nothing seems to happen for the first week. By the end of week two the battery begins to show signs of life.If at the end of week three nothing has happened, the battery is ready for recycling. Perhaps two out of three batteries cannot be recovered.

On February 25, 2014 at 10:22am
Patankar Sharad wrote:

What are the conditions that shrinks negative active material in 5 cells and 1cell having soft and mussy negative?

On March 9, 2014 at 11:19am
Mark Vanderkooi wrote:

I am interested in the comment at the beginning of this article ” To reduce corrosion on long-life batteries, manufacturers keep the specific gravity at a moderate 1.200 when fully charged, compared to 1.265 and greater for high-performing lead acid batteries.”  I just took delivery of 6 Surette dry-charged golf-cart style batteries, and duly filled them with 1.230 acid, which all we can get here in Chad, Africa where I work. I was little concerned about this, so wrote the manufacturer who told me I would lose “at least half the battery capacity” with such weak acid. Is that true? Seems a little excessive for only a 13% decrease in sulfate ions. Or is there some other mystery in the art of dry-charge such that the manufacturer did his magic assuming 1.265 and I messed all the chemistry up with my 1,230 acid? Actually, I would be happy for the extended life-expectancy - if sheer capacity is the only price I have paid, and I have not messed something else up.

On March 9, 2014 at 12:06pm
Chris C. wrote:

Mark, I am not an expert as John Fetter who posts here from time to time, but my understanding is that you are both right. Lower electrolyte density means less ions to transport electricity therefore less current producing capacity but on the other hand in a hot country such as Chad you would have greater chemical action therefore it should compensate.

What the Surette engineer is probably telling you is that you will have lower reserve capacity and you will exhaust the acid sooner, which could lead to premature sulfation, which is arguably problem number one with lead acid batteries.

Now if these batteries are constantly kept at a high charge level and properly balanced, you will minimize the risk of sulfation.

In other words, keeping a low acid density electrolyte, you should still be able to produce good current at your higher ambient temperatures while protecting the cells from long term corrosion, but you will probably experience have a lower reserve capacity as ions will exhaust sooner, and you would have to balance higher risks of sulfation with lower risks of internal corrosion.

From what I know of Surette batteries, although I am not sure about how the golf cart type are designed, is that they are very robust, which means they can take a lot of abuse that would kill lesser batteries. What is your usage scenario?

On March 9, 2014 at 1:45pm
Mark Vanderkooi wrote:

Overall, that sounds pretty encouraging. Thanks Chris. The trick is going to be equalizing on a regular basis - something I haven’t always been very good at. They are on their first charge since being filled right now. They run a 250 watt FM radio station which draws about 50 amps for an hour and a half each evening, and for 40 minutes each morning. They are recharged by solar at about 23 amps, You are right about the Surette batteries being pretty robust. I got 8+ years out of the last set on the radio station. Similar on my home.

On March 9, 2014 at 4:38pm
Chris C. wrote:

As long as you remain in C/10 or C/20 range for charge and discharge you should be fine in terms of draw versus battery capacity (in other words, 500 to 1000 AH of capacity)..

Your draw of a total of 2 hours at 50A should well be taken care of in 4 hours of direct sunshine at 25A or so, which I’m sure you should be able to get without any problems in your country wink

Equalization requires distilled water (which may be rare and expensive in your country - deionized water is another alternative), and careful monitoring of the electrolyte density of each cell.

In order to equalize you need to set your voltage such that you will force current through an already charged battery, which may require voltage to be raised to 16 or so, which can overheat the battery, so it’s important not only to monitor electolyte level (so as to keep the plates covered) but also temperature (so as to reduce corrosion and plate warpage - try not to exceed 45C).

I would suggest you do that when you know you will have plenty of sun and temperatures aren’t too high, while you don’t use power, because of the high voltages that may damage sensitive equipment. It can sometimes take several days, so it’s best to do on a regular basis, as soon as density differences between cells exceed 0.005, to minimize the time it will take to do it.

On my marine start/troll batteries, it needs to be done approximately every 3 months or so; Before I knew about equalization, my batteries would generally last 3-4 years, since then I’ve been able to get more than twice that.

During equalizing, already charged cells will bubble from outgassing while the lower density cell(s) take(s) on the charge, and those bubbling cells will have to get extra water as water evaporates from them in this process.

On March 9, 2014 at 4:44pm
John Fetter wrote:

Mark, Chris - The maximum summer temperature at the Surette factory, located far away from major cities, in the pine forests of Nova Scotia, is lower than the minimum temperature in Chad..Surette have absolutely no idea what a hot climate does to lead-acid batteries. Mark is 100% correct to use a lower SG.

On March 18, 2014 at 3:31pm
Wayne Robey wrote:

One thing to keep in mind is that the large stationary batteries have a large volume of electrolyte for the capacity so the range of specific gravity from fully charged to discharged is less than a typical golf cart battery which is physically smaller, so less electrolyte volume. Starting with a fully charged specific gravity of 1.23 seems quite satisfactory if you only discharge to the SG given by the manufacturer for the fully discharged battery then charge it. I can’t say if a stronger acid would be helpful to prevent sulfation during poor weather.

On March 18, 2014 at 4:45pm
John Fetter wrote:

An SG of 1.265 in a cold climate and an SG of 1.230 in a hot climate, at full state of charge, will provide corresponding minimum SGs at minimum state of charge. The battery operated in the hot climate does switch to a cold climate when it is discharged. It will be able to deliver the substantially the same current down to a correspondingly lower SG. The minimum SG given by the manufacturer applies to a cold climate.

On March 18, 2014 at 4:49pm
John Fetter wrote:

Correction, typo -  The battery operated in the hot climate does NOT switch to a cold climate .....

On March 19, 2014 at 3:57am
Mark Vanderkooi wrote:

It has been about 10 days since I filled the batteries (6 x 6 volts wired for 12 volts, about 1000 amp-hours total) with the 1.230 acid. I charged them for about a week up to 15.0 volts. They didn’t seem to want to go much above 15 volts, though I tried. We started actually using them two days ago, and they are performing very well. Funny thing though: many of the cells went all the way up to 1.250 or even 1.260 after charging.  Most stopped at 1.240. A few are stopped at 1.230. It sure seems that Surrete must put some sulfate in the plates in the dry charge process which go into solution when the charging cycle begins. Anyone know anything about the chemistry of dry charge? I happen to know that some of the bottles of acid I used were even less than 1.230 and suspect that the weakest cells are probably a result of that. I have evaporated some acid to make some super thick stuff - maybe 1.40 or more (haven’t tested it yet - it still out in the sun distilling) My idea is to try to balance the weakest cells with a calculated amount of this stuff. Good idea or bad idea? I know from experience in years past the in unbalanced cells just stronger get stronger at the weaker one’s expense.

On March 19, 2014 at 4:40am
John Fetter wrote:

Mark - You ARE doing it right. After filling, lengthy charging, you MUST balance the SGs. Dry-charged batteries are not totally dry. They are fully charged in the factory, most of the acid is then removed and the cells are plugged. The negatives tend to become discharged but not the positives. That is why the batteries must be charged after filling. Golf cart batteries have antimony alloy grids which have a relatively low gassing potential. You need plenty of amps to get the voltage above 15 volts.

On April 4, 2014 at 8:20pm
Santa Clara wrote:

I have problem that some batteries corroded in the internal connect (between cells) at negative side. Normally, the corrosion happen in the positive grid but why it only happen with the negative connection?

Could you please give some advice?

On June 30, 2014 at 11:20pm
David B wrote:

I have 5, 150 a/hr Gel batteries at my cabin connected to solar panels through a regulator, the batteries are 4 years old. I am finding that they show a good charge but, they do not seem to have a lot of a/hr. Why is that???  I do not live at my cabin, but use it as a weekender from time to time.

On July 1, 2014 at 7:14am
John Fetter wrote:

David - You are reading the full-charge voltage of gel batteries that are reaching the end of their useful life. If you want a reasonable battery life, use flooded batteries.

On April 18, 2015 at 9:44pm

John Fetter - how do you apply the voltage of 15.5v to 16v ( I discovered that it is necessary to get the voltage right up to at least 15.5V by slow charging). can you please explain.

On April 18, 2015 at 11:55pm
John Fetter wrote:

Nirov - I suggest using an old fashioned transformer-rectifier charger. Put the battery on charge - and wait. The voltage of the battery will slowly rise up towards the the peak value of the rectified sine wave.
The transformer secondary voltage is likely to be 12V plus two diode-drops. A 12V sine, for example, has a peak value of 12X (square root of 2) = 16.97V. The charging current falls automatically as the voltage rises, until the charger capacity and battery requirements are in equilibrium.
Alternatively use a constant current charger, set to 1A and the voltage limit set to 16V, and wait. A lab. regulated power supply can be used.

On July 17, 2015 at 1:08am
Antonio Martín wrote:

How can we find out if a battery has exploded by an internal fault or an external spark?

On July 17, 2015 at 2:29am
John Fetter wrote:

Antonio - Let me guess. Your battery exploded and you are thinking of making a claim on the supplier.
The likelihood of an internal fault causing an explosion is actually very small. The likelihood of an external spark causing an explosion is fairly high.
A short between plates is highly unlikely to cause an explosion because, if there is sparking, it will be in the electrolyte, which would quench the sparks. An internal top connector might weaken over time and, when maximum current is drawn, can break and cause a spark.
Jumper leads often cause battery explosions. People tend to be somewhat careless with the clamps.
You would need to look for a broken connection inside the battery. If there isn’t one, then it was an external spark.

On July 23, 2015 at 7:30am
Hendrix wrote:

I have a weird problem with my motorbike battery every year, I have to replace it every year so I decided to take it out of the bike and leave it on the trickle charge it during winter.
But.. that did not work, after putting it back (charger indicated fully charged) it did not even turn the starter-motor.
After recharging (only 10 minutes for the 16Ah battery with a charging current of 1A !! weird) I let it run on a 5A load and I could see a drop in voltage from 13.8 to 11.80 in 40 seconds and then after 1 minute it suddenly dropped to 10.2 volts and 30 second later it dropped to 7.2 volts.
Apparently 3 cells are damaged (how?) because they are unable to hold their charge under load.
I tried to charge for 2 hours with 14.2 volts 8A, but the result was the same…

So the big question is: Why did the battery of 4 months old die in the following 4 months on a trickle charge (measured 13.2V)

Brand is a B brand Euroglobe but the same happened to a A brand Yuasa 2 years earlier

Can anyone shed a light on this problem? What happend
And second: .... how can I preserve the battery life of my motorbike during winter…(the charger used was a Battery Tender 800mA waterproof, should I sell it on Ebay? raspberry).

On July 23, 2015 at 7:34am
Hendrix wrote:

I forgot to mention that the battery is not a maintenance free but an old-fashioned lead acid battery with the filler caps on top.

On July 23, 2015 at 9:32am
John Fetter wrote:

Hendrix - It is likely your bike alternator/ generator is not charging the battery at a high enough voltage, or you may be using the bike infrequently or only for very short trips, or the electrical load on the bike is too high. (Alternatively, it is overcharging like crazy.)
Most likely by the time you noticed each successive battery was not up to scratch, it was already too late. What is the water consumption like? Water consumption is proportional to the amount of charging.
Start the engine, run it for a few minutes at 1500 revs or more, then measure the battery voltage. Vary the speed of the engine to see how the voltage behaves. You need a fairly steady 14.4 volts at any RPM above idling. If it remains below 14 volts (or is well over 14.4 volts) there is a problem with the voltage regulator.

On July 23, 2015 at 10:46am
Hendrix wrote:

Thanks for the quick reply John.
First thing first, I was maybe not clear enough but the problem only occurs when the bike is not used for a long time.
For this reason the battery is (taken out and) connected to a charger with trickle charge function and left like that all winter.
After winter I found the battery is dead as described (while the trickle charge seems uninterrupted).
So what could have happened, the charger seems ok..(good floating voltage -> 13.2V )
And this is the third battery that did not survive the winter not use period.
Besides my question about what could have happened, I have a more important one: “how can I prevent this from happening again?”... I don’t feel like buying every summer a new battery.

On July 23, 2015 at 4:22pm
John Fetter wrote:

Hendrix- How much water are your batteries using?

On July 23, 2015 at 10:10pm
Hendrix wrote:

John Fetter- To answer your question about the water I can be very short about that but that is not me wink
The batteries did not ever use any water in their short lifespan, at least not noticeably, and were at all times within specs during use in the Bike and never needed to add water.
While on the (trickle) charger this did not change significantly, after 4 months there was only a very little difference in fluid level visible but this could not have been more than 0.5 or 1mm.
Sadly I do not have any equipment for measuring through such small hole the SG of each cell :(


On July 23, 2015 at 10:16pm
Hendrix wrote:

For more information (if needed): The type of battery is YB16AL-A2 from Euroglobe and the other was a Yuasa. (for the indication of how much 1mm fluid might be wink )

On July 23, 2015 at 11:03pm
John Fetter wrote:

Hendrix - 13.2 volts is not a good floating voltage. The batteries will not even remain charged at this low voltage. PLUS Your batteries aren’t using water EQUALS Batteries will most likely fail, as you described.

On July 24, 2015 at 12:12am
Hendrix wrote:

John Fetter- So the conclusion is that the charger is a bad product and is not actually doing what it is supposed to do?


I must say that another smart charger from a “low budget wall-mart kind of firm” works well with my car battery
My 10 year old spare car-battery is still working very well after 4 years on trickle charge ...±75% capacity left…. I sometimes need it when I let my new car battery discharge too much by not using the car in winter for more than 2 weeks…it sucks to have an alarm wink and then I leave it there for a week and then change it back. No problems there…

As I understood was, that the floating voltage is temperature dependent and is varying from 13.2V at 26 degrees Celsius to 14.2 at (sub)Zero Celsius. (my bad.. should be 13.5V at 26 degrees)

To conclude: so I guess I will sell the battery tender on Ebay (it is charging an empty battery ok) and hook up de motorbike battery during storage, only once a month to a charger, fully charge it and remove the battery from charger again… means also it has to be stored at above zero at all times…that means not in the shed but inside the house.

Still I find it astonishing that 0.3 V too low floating voltage on a fully loaded battery, will cause a nearly new battery to totally die in 4-6 months. I also understand now why the store only give 6 months warranty on motorbike batteries. I wish my motorbike had a kick starter and no ECU.. :D

Thanks for your input.

On July 24, 2015 at 1:12am
John Fetter wrote:

Hendrix - The best way to store your battery is to use a form of charging that ignores temperature - by using an old fashioned transformer-rectifier charger plus a timer. I suggest using a plug-in electric timer with a dial, a one week timer. The timer automatically switches the charger on once a week. Use the smallest “on” period, perhaps one hour, or the minimum it can provide. Applying maximum charge for very short periods once a week, once every two weeks, works well.
I have not yet come a cross an electronic charger that works properly on lead-acid. It seems their designers are not as conversant with lead-acid as they are with microchips. Most seem to design circuits that persistently undercharge the batteries. Lead-acid needs to be pushed to gassing periodically if you want long life. Charger designers reading this will probably be outraged.

On July 24, 2015 at 3:55am
Hendrix wrote:

John Fetter- Thanks for the idea, I will cook up something from my electronics box, enough old stuff to cannibalize in there raspberry

I might try to get my hands on a car rectifier / charging circuit because I found out that when a battery is just being used in a car regularly, the battery sometimes lives longer than 10 years!!! so I might cook something on the soldering table using this car charging circuit.

Apparently there is a big difference in the “in-car” charging and the so called intelligent chargers… I agree most of them are rubbish.

Thanks for the input..

On August 20, 2015 at 6:44pm
Wayne Robey wrote:

I hope John Fetter can further explain his statement “The best way to store your battery is to use a form of charging that ignores temperature - by using an old fashioned transformer-rectifier charger plus a timer”  as opposed to a trickle charge based on battery type and temperature. From a 1960 era Gould stationary battery manual, the proper float voltage for a 6 cell antimony alloyed lead battery at 25 degrees C is 13.2 volts and the TC is -.0237V/deg C. At 25 deg C the equalizing and rapid recharging voltage is 14.4 volts and I assume the TC is the same. I have built some of these chargers and find that when used as a backup battery the water consumption is negligible and specific gravity stays at or above the new level. One Exide RV battery that I know of that was never used for anything except backup developed a nearly shorted cell after 4 years but that is the only failure I know of.

On August 20, 2015 at 11:39pm
John Fetter wrote:

Wayne - Are you sure one can assume that all battery chargers manufactured in the world today are properly designed, well made? Most people like to shop around and prefer to buy on price. I suggest you might like to take the implications of that into account.

On September 2, 2015 at 12:04am
Bevan Paynter wrote:

Starter batts in many cases are never fully charged. I found only way to fully charge sli batt was after run disconnect neg lead & put 14v reg chgr on(fitted with accurate ammeter) ,when ammeter drops to almost zero batt is fully chrgd. It may amaze how much charge batt takes! Never leave batt on trickle charge! It causes posgridcorrosion. I had 2 new sli ba tts just chgr every 1 or 2 mths or when o/c volts below 12.4v. This was 4 yrs ago were new. Recently fitted 1 to car- like new performance! Incidentally,both batts were cheapest available($59 ea).

On September 29, 2015 at 7:18pm
david wrote:

john fetter where could a begginer get info on fixing a couple(transformer rectifier) old batt. chargers(50s 60s) as well as 90s junk im just more or less learning elec.-tronics repair and am probably gittin in ore my head but have more time than money to learn and have no good (true voltage) chargers worth having

On September 30, 2015 at 1:43am
John Fetter wrote:

david - Run a series of Google searches. Enter three or four words relating to your area of interest and let Google find what you want. You will find educational pieces mixed with commercial information. You might find one out of ten results will be of help. For example, “transformer rectifier battery charger”. Use different words and search again. Spend a few hours on this and you will find what you need.

On September 30, 2015 at 1:06pm
david foltz wrote:

john fetter thanks for the response this is my first time asking questions as such on these type of sites and appreciate the fast reply my last stupid question is if a vinegar and salt solution will clean corrosion and baking soda will then neutrilize that effect why couldnt a mixture like that (in a well ventilated area) be used to   desulphate the cells (of course the massive amounts of bubbling im sure that would happen) would have to be contained with a fresh water supply and a baking   soda solution thanx again

On September 30, 2015 at 5:11pm
John Fetter wrote:

david - No. Don’t put any of these things into a lead-acid battery.

On September 30, 2015 at 11:15pm
Bevan Paynter wrote:

I have found 1 teaspoon mag sulphate Epsom salts per cell is as good as anything to get more life if only type two sulphation as are electronic desulphators. EDTA or other chelators strip the sulphation so that lead is lost. Whatever, all lead acid batts have a certain life and there are no magical cures as snake oil salesmen would have you believe or even you tube posters etc!!!

On October 1, 2015 at 7:44am
david foltz wrote:

thanx for the responses it sounds like im just doomed to continual purchassing new batteries being a truckdriver leaves no time for quick type gimmicks and not comfortable leaving electricity plugged in not being able to keep track of fluid levels unless a more reliable type of desulphater   or temporary overcharging style of (maintainer)

On October 1, 2015 at 11:02pm
Bevan Paynter wrote:

What are the lifetimesof your starter batts, if you are doing long runs could be overcharging, or if lots of short runs undercharging, are batts in a cool spot under 40’c, or if doing rough roads is battbeing shaken to death? Are batts top quality? Amaron & AC Delco spring to mind as the best. Is charging system OK & connections good? Up to you!

On October 2, 2015 at 10:38am
david foltz wrote:

bevan paynter the problems im speaking of are the batteries in everything left at home while jim gone like tractors backhoe riding mower motorcycles personal p/u truck (put two new batts in)put on the charger after charged i drove it and charged/checked it everything ok left for two weeks came back home both were dead so i charged checked everything ok i disconnected them left again lil less than three wks dead again i tried a battery tender type product that the fireman said was the cause of the loss of one building i did have so im no longer comfortable leaving things plugged in so id like to be able to fix/reclaim the batts in a quick to fix (haha) process in the relatively few day layovers i have off which from everything ive studied must not exist

On October 2, 2015 at 11:21pm
Bevan Paynter wrote:

Everything locked while you away, so no one can sabotage? Would suggest you remove all batts fully charge each lock away. When return, check eachbatt to sort out what is happening.

On November 29, 2015 at 9:48pm
Asim wrote:

Why Negative Plate Shedding happened in lead acid Battery after use of 3 to 5 months. Anyone here for explain

On January 27, 2016 at 8:28pm
Ocean Littlefield wrote:

I have been seeing a lot of people on line bringing life back into old batteries by removing the acid, cleaning the battery inside with a solution of Baking soda, rinsing with water, and then filling with a solution of Alum Water.  Do you have any response to this concept?  Would you know they chemistry and why it works?  Check You Tube for Alum Battery and you will find many interesting stories.

On January 27, 2016 at 11:18pm
John Fetter wrote:

Ocean Littlefield - Yes. Have you noticed that people prefer to omit the vital detail that the battery is charged as part of the process?
Charging works. Belief sells.

On January 27, 2016 at 11:50pm
Ocean Littlefield wrote:

John, nothing is for sale here.  Actually the information I am referring to includes the charging of the battery after the Acid electrolyte is replaced with the Alum electrolyte.  It appears that Alum can serve as an electrolyte in a lead battery.  What I am asking for is if anyone knows the chemistry behind this.  How does Alum differ from Acid in it’s behaviour as an electrolyte with lead?

On January 28, 2016 at 12:18am
John Fetter wrote:

Ocean Littlefield - If two sets of all identical old batteries are used, one set treated with alum and the other left untreated, then both sets of batteries are charged identically, and thereafter the ampere-hours measured, it would be possible to say that alum works or not. Surely the explanation should come out of that, not out of a theory that people like to believe?

On January 28, 2016 at 1:24am
Ocean Littlefield wrote:

Indeed.  And I plan to try it myself as I have several old batteries.  What is at the root of my curiosity though is the longevity of the Alum Lead battery.  I understand the Lead Acid typically degrades from various things such as shedding, and sulfation.  What would be the long term effects of Alum which could be anticipated.  Of course I may only know by eventually tearing apart a Lead Alum battery once it’s finally dead.  But it would interesting to have an idea from someone who is good at chemistry.

On January 28, 2016 at 1:54am
John Fetter wrote:

Ocean Littlefield - Enthusiasts have been dabbling with alum in lead-acid batteries for over 100 years. They are still dabbling. Belief is the driver.

On February 11, 2016 at 6:39pm
Steel Cycler wrote:

Let’s say I buy a new battery and remove a measured amount of electrolyte from each cell then replace with equal amount of distilled water. The goal is extended life, and reduced capacity is acceptable. Keep the electrolyte to add if more capacity is needed later.
  Is it best to remove electrolyte at high or low SoC? Any difference in how the modified battery is optimally maintained? 
  In the article above it says “To reduce corrosion on long-life batteries, manufacturers keep SG at a moderate 1.200 fully charged”

On February 11, 2016 at 11:22pm
John Fetter wrote:

Steel Cycler -  Reducing the SG drastically will not only reduce the capacity but also the life expectancy of the battery.
When the battery is discharged and the already low SG drops to fractionally above that of water, any charging applied thereafter will be accompanied by electroplating due to the fact that lead will begin to dissolve out of the positive plates and into the weak acid and will cause dendrites to form on the negatives. These dendrites will quickly bridge the separators and short out the plates.
If you want to reduce the SG, you need to increase the volume of the electrolyte, in order to retain the same quantity of sulfuric acid. The acid participates in the charge-discharge reactions.
Corrosion is caused by overcharging. A fully charged battery with a high acid SG sitting on the shelf will suffer no corrosion.

On September 15, 2016 at 4:02am
Ed Lithgow wrote:

Expert opinion here seems fairly unconvinced by (many at least of)  the “smart” battery chargers on the market, and also seems to be advocating mild systematic overcharging.

In view of this, what’s the opinion on the relatively cheap unregulated solar chargers, which start at about 1.5A capacity? I’m in Taiwan, so sunlight is usually in excessive supply.

I don’t drive very much, and, perhaps as a result, my batteries seem to have a fairly short life. I have a “smart” battery charger and put the battery on that when its discharged, but by the time I find out its probably been discharged for a while.


“The RC intelligent smart battery charger have multi-stage distinct operating mode : Constant Current (CC) / Constant Voltage (CV) / Equalizing Charge / Floating Charge Method.”

The charger has three levels of charge, but right now will only apply the lowest level (about 1A) to the discharged car battery, which, assuming the charger is OK, probably means the battery is due for replacement. Again.

On September 26, 2016 at 5:32pm
Anita wrote:

To John Fetter
On February 11, 2016 at 11:22pm
Interesting your statement
Does it mean that the amount of sulphuric acid is directly proportional to plate surface area?
If so how does telephone batteries (SG 1.2) last long while lift truck batteries (SG 1.3) have high output and I guess short life?

About the dendrites, would you recommend to charge batteries with a large capacitor across the battery to kill dendrites as they grow?


On September 28, 2016 at 7:39am
John Fetter wrote:

Anita - In answer to your questions and in context:
No. The amount of sulfuric depends on how much is put into the battery.
No. Telephone batteries don’t do much work. Deep cycling reduces battery life.
Very high ripple promotes dendrites. Normal charging does not promote dendrites.

On October 4, 2016 at 2:39am
Lim G wrote:

I am new in this field but spending some good evenings in the last 2 weeks reading thru this site and some others which I have gained some info from experts like John Fetter, Chris C, and many others. I have got an old discarded battery from a car workshop to be meant for recycle. Anyway, typical life of car battery over in this part of region is between 1 to 2 years. Most car battery warranty is 1 year. hard to find one for 2 years.

Took home and start meddling with it. It is Yuasa Ecor, Japan made, lead acid supposedly maintenance free, maybe 30 to 40 Ahr, model 40B19L .
Remove the label on top, and all 6 cells electrolyte is above the plates. Voltage open circuit was 11.4V. Charged it for 2 days using old transformer with rectifier type where open charger v is 17v.  After 2 days, remove charger and after few hours v dropped to about 12.9V. Put into car and was able to start the car. Remove from car and load it with some LED about half amp current. After 2 hours, v dropped to 10.8 V.
Charged the battery again for 2 days, but this time noticed that all cells except cell 5( count cell 1 as nearest to negative battery terminal) does not bubble.
After charging, and then resting for few hours, and then connect to half amp load, v dropped back to 10.8 volts. Took measurements of the cell voltage. Measurement is taken with negative probe at negative terminal and positive probe at individual cells starting from cell 1,2, 3,4,5,6 and lastly positive terminal. Below are the measurements..

Cell 1and negative terminal = 0.423
Cell 2and neg term = 2.55
cell 3 and neg term= 4.69
cell 4 and neg term = 6.82
cel 5and neg term = 8.94
cell 6 and neg term = 9.14
batt pos term and neg term = 10.85

Calculating the differential, the voltages are
cell 1 and neg term = 0.42
cell 2 and cell 1 = 2.13
cell 3 and cell 2= 2.14
cell4 and cell 3 = 2.13
cell 5 and cell 4= 2.12
cell 6 and cell 5 = 0.2
term positive to cell 6 = 1.71
Total = 10.85 volts

The SG of all cells is 1.31 except cell 5 is at 1.22.

1. How do one measure the voltage of individual cell as I cannot access the positive and negative end plates of each cell?
2. I do not have any idea how the plates are connected between cells, but based on the low SG and also volt between cell 5 and 6 is so low, does it mean cell 5 is shorted?
I have a picture of the cell but cannot figure out what is it , whether it is sulphates, dendrites, plates warped, or corrosion?. I can send picture but how to send?

I will continue to charge for a few more days, and see whether I have luck or should I just abandon hope, and no way to recover this cell.
Please advise.
Thank You.



On October 5, 2016 at 4:35am
Lim G wrote:

Sorry, correction here. All cells bubble upon charging except cell 5.

On March 27, 2017 at 3:37pm
Rosco wrote:

Trying to return a couple large (Group 4D) lead-acid batteries to service after sitting about 6 years. After charging for a week on a BatteryMinder 128CEC1 the two center cells of one of the batteries have come up to 1.240 and 1.265 S.G. The other cells are all around 1.100 Found electrolyte coming out of the 1.265 cell and the battery was quite hot. The charger had been delivering 8A. I took the battery off charge. It occurs to me that the 1.265 cell might be shorted,and all the energy going into that once cell explaining the bubbling in just that cell but I expect the S.G. would not have risen in a shorted cell. Is that true?
The other battery looks better to the charger. When I took it off charge after a week the charger said it was fully charged but the “weak battery” lamp was on. The S.G readings were poor, ranging from 1.100 to 1.165
I obtained these batteries and a couple dozen big Trojan deep cycle batteries with a property I bought. I hope to bring any of them that can be saved back to life. Per the Batteryminder instructions, it could take weeks to assess each battery. Any advice on how to identify any batteries that are beyond saving in any quicker method?

On September 20, 2017 at 4:55am
Jumaleen rose ursula wrote:

If an ownered type jeep(american old style jeep) has been exploded during a drive test, is it possible then that it will affect the other parts of the unit and get damage from that explosion?or what will happen to its affected areas?

On October 4, 2017 at 1:47pm
William D. Guentzler wrote:

Can a 6 volt wet cell battery have an internal short and explode and still have a small voltage at each cell eg. .80, .76, .76 volts?

On November 11, 2017 at 5:27pm
Reginal L. Gilbert II wrote:

I would like to know if there can be an internal circuit configuration of our cell phones that may contribute to the apparent power losses we currently experience with them ?

On December 9, 2017 at 1:29pm
Bill Guentzler wrote:

I have a Trojan 6 volt T145 battery that suffered from an explosion, caused by a “soft short”, lead dropping, poor manufacturing, poor maintenance from not adding H2O, and/or a combination of those mentioned above, yet after the fact still measures 2.32 volts across the three cells, from the positive to the negative.  Is this common, and how can it be explained?