Why We Also Need Flooded Lead Acid Battery?


The electrode of a flooded lead-acid battery is mainly composed of lead and its oxides, and the electrolyte is a sulfuric acid solution, which is also called wet lead-acid battery with the advantages of stable voltage and low price. In the discharge state of a lead-acid battery, the main component of the positive electrode is lead dioxide, and that of the negative electrode is lead. In the charge state, the main component of the positive and negative electrodes is lead sulfate.

When the dry battery of flooded lead-acid battery using first, add the original battery solution(dilute sulfuric acid), and then add the distilled water. If need to treat the plate vulcanizing, it is possible to pour out the electrolyte for cleaning. Therefore, the use process is relatively complicated. Another maintenance-free sealed lead acid battery is simple to maintain during use, and so it has an 80% market share in the market and has a tendency to replace the dry battery of flooded lead-acid battery. Does it mean that there is no market for a wet lead-acid battery? The answer is negative. Let us explore the reasons below.

Let us first learn the development history of the lead acid battery.

1. 1860

The Frenchman G.Plante achieved the first lead-acid battery using dilute sulfuric acid as the electrolyte and making the lead plates form active materials by repeated charging and discharging.


With the advent of DC generators, the lead-acid battery has reliable power.

3. 1881

Sellon invented the lead-antimony alloy grid. Faure invented the method of applying the paste on lead to form active materials.

4. 1882

Cladstone and Tribe put forward the vulcanization theory, and then a recognized chemical reaction formula is established.




Udor and Lucas completed a convenient forming method of a positive plate (electrolyte plus corrosive).

7. 1910

Exide Company introduced the tubular positive plate.

8. 1935

Haring and Thomas invented the lead-antimony alloy grid. Slegler invented the glass filament tube which replacing the rigid rubber tube used for the tubular plate.

9. 1970

Deviff created the first valve regulated battery with a lean-liquid structure.

10. 1975,

GatesRutter obtained an invention patent for a D-type sealed lead acid dry battery, which has become the battery prototype of VRLA.

11. 1979,

After purchasing the patent from Gates, GNB invented the MFX positive grid alloy, and began large-scale publicity, and produced the large capacity liquid-absorbing maintenance-free sealed lead-acid battery.

12. In 1984

VRLA battery is used in small range applications in America and Europe.



With the rapid development of the telecommunications industry, the VRLA battery has been quickly promoted and used in the telecommunications sector.

2. Reasons and methods for adding liquid of flooded lead acid battery

2.1. Reasons for adding liquid

The lead-acid battery stock solution is diluted by sulfuric acid and pure water. Usually, the battery stock solution needs to be added when the dry battery is used first. The lead-acid battery replenishment fluid is distilled water, and the replenishment fluid should be added in the case of battery water loss or vulcanization.

The battery water loss means that the battery will release hydrogen and oxygen during the electrochemical process, which will be released from the safety value. Water is composed of hydrogen and oxygen. Losing hydrogen and oxygen is equal to losing water.

The loss of water also brings serious vulcanization, and the battery capacity decreases, which leads to thermal runaway and deformation of the positive electrode plate, and the battery shape expands and is completely scrapped. Usually, the battery should do the water replenishing maintenance after using 6 months.

The battery vulcanization is caused by the formation of a layer of large particles which is hard crystals on the surface of the negative plate inside the battery, and it cannot be peeled off after charging and cannot be converted into lead sulfate as the active material. This is called irreversible sulfation or vulcanization. Adding the replenishment fluid can further extend the battery life.


2.2. Method of adding liquid

Open the safety value on the lead-acid battery, and everyone can directly see the inside of the lead-acid battery. The safety value of the lead-acid batter is located under the safety value cover of the lead-acid battery. The safety value cover is usually glued or ultrasonically welded to the big cover of the lead-acid battery. Do water replenishing for lead-acid battery in accordance with the following operating procedures.

2.2.1 Preparation. Distilled water, Tools: screwdriver, straw( can be replaced by disposable needle tube), transparent polyethylene tube, straw suction mouth for suitable diameter, ABS glue.

2.2.2 Unscrew the safety value directly on the top cover of the flooded lead acid battery. There is still some filler around the rubber cap, pay attention to remove the filler.

2.2.3 Inhale the prepared distilled water with a straw and inject the distilled water from the exhaust hole.

2.2.4 Cover the exhaust hole of the lead-acid battery filled with electrolyte with a breathable shield to prevent dust from falling into the exhaust hole. Let stand for 24 hours to see if there is an active electrolyte (free acid) inside the exhaust hole.

3. Comparison of flooded lead-acid battery, valve regulated lead-acid battery and wound lead-acid battery

3.1 Flooded lead acid battery

The most commonly used start-up battery on trucks is the flooded lead-acid battery with a low price and large discharge current at low temperatures. Because the internal working medium is a solution of water and sulfuric acid, the water will inevitably evaporate and electrolyze during use, so adding the distilled water regularly to ensure the height of the liquid level.

It is because of the characteristics that require maintenance that this type of battery is often scrapped and damaged due to improper maintenance during use. Not everyone can maintain it correctly. For example, when the electrolyte level is lowered, add the distilled water, but someone will mistakenly add the battery stock solution, causing the sulfuric acid concentration to be too high, or replenishing the battery with mineral water or poor quality distilled water, and the battery will be damaged and scrapped with a short time.

In addition, the performance of tolerance vibration of plates of the flooded lead-acid battery is poor. With the bumpy vibration during use, the active materials on the plate will fall off, resulting in the effective reaction area of the plate continuously reducing. When the falling off active materials accumulates to a certain height at the bottom of the battery, it will cause a short circuit of the plate, serious self-discharge, and the battery to be scrapped.

The flooded lead-acid battery with electrolyte cannot be stored for a long time and must be installed in the vehicle. The battery will be self-discharged. When the battery capacity is insufficient for a long time, the electrode plate of the battery will undergo irreversible vulcanization, which will eventually lead to scrap.

3.2 Valve regulated lead acid battery

Valve regulated lead-acid battery is actually an upgraded version of an ordinary lead-acid battery. It had a fully enclosed shell structure and does not need to be maintained during use. It does not replenish the distilled water frequently.

In addition to being maintenance-free, this kind of battery has better shock resistance than an ordinary battery, but the valve regulated lead acid battery price is relatively more expensive. Its overall lifespan is not much better than that of an ordinary lead-acid battery, so the overall use cost will be slightly higher than the ordinary lead-acid battery. The low-temperature discharge capacity of value regulated sealed lead acid battery is not as strong as that of a flooded lead-acid battery.

3.3 Wound lead acid battery

Many people may not have known the wound lead-acid battery. The biggest difference between the wound lead acid battery and the ordinary lead-acid battery is that the structure is different. The wound type has a spiral structure, while the ordinary battery has a flat plate structure. It features large starting power, long service life, fast charging, and small self-discharging, strong vibration, and impact resistance. It can work normally in 55℃-75℃.In addition, it has a solid structure inside, so it has very strong vibration resistance and can withstand four times stronger vibration than a flooded lead-acid battery.

Its internal structure is spiral type, and the electrolyte is all absorbed by the battery separator without flowing liquid, so it can be used normally even in an inverted state. In addition, the wound battery can output three times stronger current than an ordinary battery, which is very suitable for use during a cold start in winter.

The self-discharge of the wound battery is very small, and it can even start the vehicle after being fully charged and stored for one or two years. This is beyond the reach of an ordinary battery. Although the wound battery performance is perfect, the price is too expensive. It is currently only used in some high-end passenger cars, and the amount of truck usage is almost negligible. However, if someone has special requirements, one can also consider replacing the ordinary battery with a wound battery, as long as you can accept this high price.

4 Conclusions

Although the flooded lead-acid battery feature-poor vibration resistance, short life, troublesome maintenance, it also has the advantages of extremely low cost and high working voltage, this type of battery are still used on some products with strict cost control such as a lead-acid battery for electric bike, light trucks and etc. As long as the battery is regularly maintained in the later period and finding out the problems in time, the deficiencies of such battery can also be compensated and extending the service life to the greatest extent. The flooded lead-acid battery will exist for a long time.

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