Patina damnum analysis

The electrolyte in the lead-acid battery is as valuable as the blood in the human body, and once the electrolyte is lost, it means that the battery is scrapped. The electrolyte is composed of dilute sulfuric acid and water. During the charging process, it is difficult to avoid water loss, and the charging mode is different, and the water loss is also different. Ordinary three-stage charging mode, the water loss during charging is more than twice that of Collin pulse mode! In addition to the natural life of the battery, there is a water loss life: a single battery loses more than 90 grams of water, the battery is scrapped. At room temperature (25 ° C), the water loss of the ordinary charger is about 0.25 grams, while the Colin pulse is 0.12 grams. At high temperatures (35 ° C), the water loss of the ordinary charger is 0.5 grams, while the Colin pulse is 0.23 grams. According to this calculation, the ordinary charger will be dry after 250 cycles, and the Colin pulse will be dry after 600 cycles. As a result, the Collin pulse can extend the battery life by more than double.

① aqua damnum ② vulcanization ③ quapiam intemperie ④ thermal runaway (filled drum)

The first two (1) and (2) account for 97% of battery damage on the market.

(1) Analysis ① : The main causes of lead-acid battery water loss

Electric vehiculum patina

The electrolyte in the lead-acid battery is as valuable as the blood in the human body, and once the electrolyte is lost, it means that the battery is scrapped. The electrolyte is composed of dilute sulfuric acid and water. During the charging process, it is difficult to avoid water loss, and the charging mode is different, and the water loss is also different. Ordinary three-stage charging mode, the water loss during charging is more than twice that of Collin pulse mode! In addition to the natural life of the battery, there is a water loss life: a single battery loses more than 90 grams of water, the battery is scrapped. At room temperature (25 ° C), the water loss of the ordinary charger is about 0.25 grams, while the Colin pulse is 0.12 grams. At high temperatures (35 ° C), the water loss of the ordinary charger is 0.5 grams, while the Colin pulse is 0.23 grams. According to this calculation, the ordinary charger will be dry after 250 cycles, and the Colin pulse will be dry after 600 cycles. As a result, the Collin pulse can extend the battery life by more than double.

The big problem of lead-acid battery in the process of charging is gas extraction.

According to the study of the causes and rules of gassing in the charging process of lead-acid batteries by American scientist J.A.Mas, in order to achieve a very low gassing rate, lead-acid batteries can accept the charging current curve as follows:

The formula for the critical gas evolution curve is: I=I0e-at %h^2

In the charging process, the charging current exceeds the part of the critical gas evolution curve, which can only lead to the electrolytic water reaction of the battery to produce gas and temperature rise, and can not improve the capacity of the battery

① In the constant current charging stage, the charging current remains constant, the charged electricity increases rapidly, and the voltage rises;

In the constant voltage charging stage, the charging voltage remains constant, the charged electricity continues to increase, and the charging current decreases;

③ The battery is full, the current drops below the floating charge conversion current, and the charging voltage decreases to the floating charge voltage;

(4) During the floating charging phase, the charging voltage remains the floating charging voltage;

The common three-stage charging stage is constant current charging, which is mainly to take into account the design of the circuit is more convenient, not to make the battery performance is very good.

At the late stage of constant current charging and the early stage of constant voltage charging (shadow area), the current exceeds the critical gas evolution curve, causing the gas evolution of the battery and causing the life decline.

The current exceeding the critical gas evolution curve only causes the battery to produce gas and temperature rise, and does not convert into battery power, and the charging efficiency is therefore reduced.

(2) Analysis ② : the cause of lead-acid battery vulcanization

Long-term battery retention, long-term overcharge and undercharge in the charging process, and large current discharge in the use process can easily cause the vulcanization of the battery. Its appearance is: a light, a full, we call it the "false damage" of the battery. Sulphide substance sulfate adhered to the plate, reducing the reaction area between the electrolyte and the plate, so that the battery capacity rapidly attenuated. The loss of water will increase the vulcanization of the battery; Vulcanization will increase the water loss of the battery, and it is easy to form a vicious cycle.

(3) Analysis ③ : the imbalance of lead-acid batteries

A battery consists of three or four cells. Due to manufacturing process problems, it is not possible to achieve an effective balance of each battery, ordinary chargers use the average current, so that a single battery with a small capacity is full first, and the formation of overcharge, when discharging, the small capacity of the battery is released first, and the formation of overdischarge. In the long run, the vicious cycle makes the whole group of batteries lag behind, so that the whole group of batteries are scrapped. The floating charge stage of the three-stage charger has a small current of 500mA, and its role is to compensate for charging and make the battery full. However, it also brings two side effects :1, after full, the excess current is not broken, electric energy is converted into heat energy, water decomposition, accelerate the distribution of water; 2, small current charging, the resulting current bifurcation is large, more likely to cause the imbalance of the battery pack.

(4) Analysis ④ : the thermal runaway problem of lead-acid batteries

Battery deformation is not sudden, often there is a process. When the battery is charged to 80% of the capacity, it enters the high-voltage charging area. At this time, oxygen is precipitated on the positive plate, and oxygen passes through the hole in the partition to the negative electrode, and oxygen is reactivated on the negative plate: 2Pb+O2(oxygen)=2PbO+Q(heat); PbO+H2SO4=PbSO4+H2O+Q(heat). When the reaction produces heat, when the charging capacity reaches 90%, the oxygen generation rate increases, the negative electrode begins to produce hydrogen, a large amount of gas increases the internal pressure of the battery exceeds the valve pressure, the safety valve opens, the gas escapes, and the final performance is water loss. 2H2O is equal to 2H2↑+O2↑. As the number of battery cycles increases, the water gradually decreases, resulting in the following conditions for the battery:

(1) The oxygen "channel" becomes smooth, and the oxidation generated by the positive electrode can easily reach the negative electrode through the "channel";

(2) The heat capacity is reduced, the heat capacity of the battery is very large, after the loss of water, the heat capacity of the battery is greatly reduced, and the heat generated makes the battery temperature rise quickly;

(3) Due to the shrinkage phenomenon of the ultrafine glass fiber separator in the battery after water loss, the adhesion with the positive and negative plates becomes worse, the internal resistance increases, and the heat generated during the charge and discharge process increases. After the above process, the heat generated inside the battery can only be dissipated through the battery slot. If the heat dissipation is less than the heat output, the temperature rises. As the temperature rises, the overpotential of the battery gas evolution decreases, the volume of gas evolution increases, a large amount of oxidation of the positive electrode passes through the "channel", reacts on the surface of the negative electrode, emits a large amount of heat, so that the temperature rises rapidly, forming a vicious cycle, the so-called "thermal runaway".