Sulfurization and removal methods for lead-acid batteries
update time:2022-09-27 hit count:428次

1.  Overview

Lead-acid battery technology has basically remained unchanged over the past 100 years.  Although there have been improvements in chemistry and structure, there is a common factor that causes failure.  The cause of this failure is: sulfate accumulation on the plate leads to failure.  The solution to these problems is to apply pulse technology.

Pulse technology helps eliminate these battery faults.  It can maintain a high active material reaction, make the battery internally balanced, and easily accept external charging.  In this way, various related costs caused by battery replacement are saved.

2.  Technical introduction

Experts predict that lead-acid batteries will continue to be the dominant battery power source into the next century.  However, a problem worthy of attention is that the working status of most batteries cannot meet the needs of today's technological transportation.  It is said that the reactive materials of lead-acid batteries can last for 8 to 10 years or longer, but in fact it cannot.  The current average battery life is 6-48 months.  Only 30% of batteries can last for 48 months.  Most batteries age and fail prematurely.  The cause of a series of problems that affect battery life is: sulfate build-up, and the solution to these problems is pulse technology.

As early as 1989, pulse technology was used to improve the practicality of batteries and extend battery life.  Its working principle: to maintain a high active material reaction in the battery, making the battery internally balanced and easy to accept charging.  This technology provides a large discharge capacity, accepts charging quickly, and can be used for a long time.  (In other words, extend battery life)

Now let’s take a look at how pulse technology benefits batteries and how it works.  First, let us review the working principle of the battery: According to the 11th edition of the Battery Council Manual: "Battery is a design category based on electrochemical principles.  The electrical energy generated by the battery is converted from stored chemical energy.  In vehicles and power machinery and equipment Requires batteries, its three main functions are:

(1) Supply power to the ignition system to start the engine.

(2) Supply power to electrical equipment outside the engine.

(3) It stabilizes the voltage of the electrical system, smoothes the output and reduces the momentary high voltage in the electrical system. "

The battery is composed of two different materials (lead and lead dioxide).  The two materials react in a sulfuric acid solution to generate voltage.  During the discharge process, the active material on the positive lead plate and the sulfate radicals in the electrolyte generate PbSO4.  At the same time, the active material on the negative plate also reacts with the sulfate radicals of the electrolyte to generate PbSO4.  Therefore, as a result of the discharge, both the positive and negative plates are covered with lead sulfate (PbSO4).  The battery is restored by charging it in the opposite direction.

During the charging process, the chemical reaction state is basically the reverse reaction of discharge.  At this time, the lead sulfate (PbSO4) on the positive and negative plates decomposes into its original state, that is, lead and sulfate.  Water decomposes into "H" and "O" atoms.  When the separated sulfate combines with "H", it is reduced to Sulfuric acid electrolyte.

From the above, the basic working principle of the battery is the energy formed by the chemical reaction process of ion exchange between sulfuric acid and lead.  During the energy exchange process, the reaction product-lead sulfate is "temporary" on the plate.  However, it is worth noting that during the charging and reduction process, not all the lead sulfate on the plate can be dissolved and piled up on the plate.  This accumulation is the residue of the electrochemical reaction and occupies the position of the plate.  This means that the reactive material of the plates is constantly decreasing, which is the main cause of battery failure.  (Battery failure due to lead sulfate is commonly known as plate salinization)

Plate salinization problem: Most battery failures are attributed to lead sulfate buildup.  When the energy of the lead sulfate molecules is greater than a low value, they dissolve from the plates and return to the liquid state.  Then, they can accept recharging.  But in fact, there is always a part of the sulfate that cannot return to the electrolyte, but adheres to the plate to form insoluble crystals.  Sulfate crystals are formed in this way: the core energy of these individual sulfate molecules that cannot participate in the reaction is in an extremely low state, and it gradually absorbs other sulfate molecules with extremely low energy.  When these molecules stack up and combine tightly, they form a crystal.  This crystal cannot be dissolved into the electrolyte.  The existence of these crystals occupies the position of the electrode plate, causing the electrode plate to lose its ability to charge and discharge.  Therefore, this point or part of the plate that is covered is equivalent to a dead center.

According to page 58 of the BCI manual: "The essence of a battery is a chemical device, and its charging characteristics are often changed by the chemical changes of the battery itself.  For example, sulfate should be a normal chemical reaction product, but under abnormal conditions , it becomes excess material and becomes a major problem affecting chemical reactions, and these excess sulfates continue to accumulate on the plates and are ignored for a long time.  In addition, new batteries will also appear in this state if they are stored for too long.  When the battery is severely salted, it cannot accept the fast and full recharge from the generator.  Similarly, it cannot be discharged satisfactorily.  As the saltation intensifies, the battery will fail because it cannot accept charging and discharging." No. 56 The page says: "Charging voltage is affected by factors such as temperature and electrolyte concentration, the area where the electrolyte contacts the plate, the age of the battery, the purity of the electrolyte, etc.  The salt crystals on the plate are very hard, which increases the internal resistance. "

More than 80% of batteries fail due to the accumulation of these salt crystals.  The speed, area and hardness of these crystal formations are closely related to time, battery charge status, and the life of the energy reserve.  The accumulation of salt crystals on batteries is very troublesome.  Salinization is inevitable in the following situations:

1. The battery has been stored for a long time before installation and use.  In fact, once the sulfuric acid solution is added to the battery, a chemical reaction begins to produce salts.  Therefore, new batteries will also be salted when left aside, causing the new batteries to fail shortly after being installed on the transportation vehicle.

2. The vehicle remains stationary for a long time without working.

3. The battery is corroded and the internal resistance increases during charging, causing insufficient charging.

4. Continuous over-discharge.

5. Temperature influence.  For example, when the temperature becomes hotter, the salinization rate doubles for every 10 degrees increase in temperature.  During charging, if the outside temperature is high and the battery temperature reaches 75 degrees, the internal resistance will increase, resulting in insufficient charging.  When the temperature turns colder, the vehicle's lubricating oil thickens, which requires more power to start the vehicle, which means that the battery needs more discharge capacity.  As a result, the accumulation of salts on the plate is accelerated.  If you pay attention to the over-discharge of the battery, you will know that the battery electrolyte solidifies at this time, which greatly damages the plates.  Under normal circumstances, when the battery is fully charged, the specific gravity of the electrolyte is about 1.27, and the solidification temperature of the electrolyte at this time is –83 degrees Fahrenheit; when the specific gravity is about 1.2, the solidification temperature is –17 degrees Fahrenheit; if the specific gravity is about 1.14 (also known as Fully discharged), which solidifies at only 8 degrees Fahrenheit.

6. In the case of insufficient charging, the battery cannot supply starting current, which often causes misfires in frequently used vehicles.  According to the BIC manual: "When a vehicle uses an undercharged battery, it may cause the engine to slow down and idling, unable to start, consuming electric energy.  In turn, the battery cannot be charged by the generator at high speed.  As a result , although the battery is charged all day long, it still cannot be fully charged.  And the battery is frequently undercharged, and the battery becomes more salinized.  If this vicious cycle continues, the battery will completely fail.

To sum up, sulfate is inevitable in the energy conversion process, but the crystallization of sulfate is indeed a serious problem, not the sulfate itself.  This requires more people to understand the seriousness of this problem - sulfate crystallization render the battery useless.

The symptoms of its failure include:

1. Plate bending: There are sulfate crystals somewhere on the plate, which weakens the acceptance of electrical energy, causing overcharge somewhere on the battery plate.  This overcharging increases the temperature here, causing the plate here to bend.

2. Saltation causes the reactants in the grid mesh on the electrode plate to fall off, which can lead to overcharging and bending of the electrode plate.

3. Short circuit: Due to the increase in internal resistance due to salinization, the plate is bent and contacts the plate of the other polarity, resulting in a short circuit or damaging the frame supporting the plate.

4. Shedding of active materials: Salted crystals increase internal resistance, causing local overcharging, causing cracks and cracks in the plate to fall off.

Therefore, it is appropriate to apply pulse technology to protect the plates, and it can also help reduce damage to the battery plates caused by mechanical vibration.  In the past, after batteries were salted, they were considered useless and discarded, or taken to a distant location for repair.  But now, pulse technology can solve this problem very well.

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