Lead-acid Battery Charging Principle

Lead-acid Battery Charging Principle

Date:Aug 02, 2019

Brief Introduction

The so-called battery is an electrical chemical device that stores chemical energy and discharges electric energy when necessary.

The main components of a lead-acid battery are as follows:

Positive plate (lead peroxide. PbO2) ---> Active material

Negative Electrode Plate (Sponge Lead.Pb) ---> Active Substance

Electrolyte (dilute sulfuric acid) ---> sulfuric acid H2SO4 + water H2O (about 37%)

Battery case

Isolation board

Other (liquid port plug, lid, etc.)

Principle and action

The anode (PbO2) and the cathode (Pb) in the lead storage battery are immersed in the electrolyte (dilute sulfuric acid), and 2V of electricity is generated between the two poles. According to the principle of the lead storage battery, the anode and the cathode and the electrolyte will be charged and discharged. The following changes have occurred:

(anode) (electrolyte) (cathode)

PbO2 + 2H2SO4 + Pb ---> PbSO4 + 2H2O + PbSO4 (discharge reaction)

(lead peroxide) (sulfuric acid) (sponge lead)

(anode) (electrolyte) (cathode)

PbSO4 + 2H2O + PbSO4 ---> PbO2 + 2H2SO4 + Pb (Charging reaction)

(lead sulfate) (water) (lead sulfate)

1. Chemical changes in discharge

When the battery is connected to an external circuit, the dilute sulfuric acid reacts with the active material on the anode and anode plates to form a new compound, "lead sulfate." It is released from the electrolyte via the discharge sulfuric acid component, and the longer the discharge, the thinner the sulfuric acid concentration. The consumed component is proportional to the amount of discharge. As long as the concentration of sulfuric acid in the electrolyte is measured, that is, the specific gravity is measured, the amount of discharge or the amount of residual electricity can be known.

2. Chemical changes in charging

Since the lead sulfate produced on the anode plate during discharge is decomposed and reduced to sulfuric acid, lead and lead peroxide during charging, the concentration of the electrolyte in the battery gradually increases, that is, the specific gravity of the electrolyte rises, and Gradually returning to the concentration before discharge, this change shows that the active material in the battery has been reduced to a state where it can be re-powered. When the lead sulfate of the two poles is reduced to the original active material, it is equal to the end of charging, and the cathode plate is Hydrogen is produced, and the anode plate generates oxygen. When charging to the final stage, the current is almost always used in the electrolysis of water, so the electrolyte is reduced. In this case, it should be supplemented with pure water.

Battery construction

For electric vehicle batteries, the following conditions must be met:

◎ High performance

◎ Shockproof and impact resistant

◎ Long life

◎ Easy maintenance
Since the glass fiber tube type lead storage battery is produced by accumulating a plurality of experimental results, it has many advantages.

1. Plate

According to the battery capacity, choose the appropriate size plate and quantity combination. During charge and discharge, the bipolar active material repeatedly expands and contracts as the volume changes. Among the bipolar active materials, the bonding strength of the spongy lead of the cathode plate is strong, and the bonding strength of the lead oxide of the anode plate is weak, so that it will fall off slowly at the time of charge and discharge, which is why the life of the lead battery is limited. . The battery life is extended, the shock resistance and impact resistance are improved, and the improvement of the anode plate becomes an urgent task.

Glass fiber tube anode plate: This is made of glass fiber hose connected to a lead alloy lattice (ruple gold). After the lead powder is filled between the hose and the core, the hose is sealed. It changes and produces an activating material, which is a very good electrode material because the activated material does not fall off and is in good contact with the electrolyte. The use of batteries with such plates is the only option for electric vehicles. The braided hose is made of 9 microm (μ) glass fiber braided bag, which is elastic, resistant to expansion or contraction, and has excellent permeability to electrolyte. This hose is the best product for a long time. , practical performance is good.

Paste plate: It is a paste made of dilute sulfuric acid, which is coated on a grid made of lead alloy and dried to form an active material. This method has been used on the cathode plate of lead storage batteries, and is also used in the battery anode plates of automobiles and minivans.

2. Isolation board

It can prevent short circuit between the anode and cathode plates, but it will not hinder the flow of ions between the two electrodes. Moreover, it will not deteriorate or release impurities after long-term use. Lead storage batteries generally use a gel separator.

3. Battery case

Strong acid resistance and mechanical strength. The battery case for electric vehicles is specially treated with a strong synthetic resin. The mechanical strength is particularly strong, and the upper cover is also made of the same material to be hot-melted.

4. Electrolyte

The specific gravity of the electrolyte is 20 ° C, and the standard weight of the electrolyte when the battery for electric vehicles is fully charged is 1.280.

5. Liquid port plug

The function of the liquid port plug is to discharge the gas generated during charging and to replenish pure water, and to measure the specific gravity.

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