- Effect of temperature on battery performance
It can be seen from the reaction equation that PbO2 is on the positive plate and Pb is on the negative plate. The conductivity of these two substances changes very little with temperature. Therefore, it can be said that the temperature effect of battery discharge performance is caused by sulfuric acid, because only its activation performance (dissociation degree and ion migration speed) is related to temperature.
lead-acid battery has high temperature of sulfuric acid electrolyte and more capacity output; When the temperature of electrolyte is low, the capacity output is less. The reason for this situation is not only due to the decrease of temperature, but also due to the decrease of the solubility of lead sulfate in sulfuric acid electrolyte when the temperature decreases, which will inevitably saturate the lead ions around the electrode plate and force the formed lead sulfate crystal to be dense. This dense crystal hinders the full contact between the active material and sulfuric acid electrolyte, so as to reduce the capacity output of lead-acid battery. The influence of temperature on the capacity can usually be roughly calculated, The capacity increases or decreases by 1% when the temperature increases or decreases by 1 ℃ When the lead-acid battery is discharged, if the sulfuric acid electrolyte temperature is high, it will reduce the supersaturation of PbSO on the surface of the electrode plate in the sulfuric acid electrolyte, which is conducive to the formation of loose lead sulfate crystals and the formation of a thick and solid PbO2 layer during charging, so as to prolong the service life of the active material of the electrode plate. If the temperature of electrolyte is too high during charging of lead-acid battery, the diffusion of electrolyte will be accelerated and the corrosion of electrode grid will be intensified, which will shorten the service life of lead-acid battery.
Practice shows that:
① When the lead-acid battery is charged, the corrosion of electrode plate and lead alloy grid increases with the increase of electrolyte temperature;
② In lead-acid battery, the corrosion of positive lead alloy grid is much greater than that of negative lead alloy grid.
Therefore, the rise of electrolyte temperature in the charging process of lead-acid battery is not welcome. In order to obtain better low-temperature electrical performance, we selected the electrolyte density of starting battery as 1.28g/cm ³ （25℃）。 Because at this density, the resistivity of sulfuric acid electrolyte at – 20 ~ – 30 ℃ is lower than other density values. If the battery does not work under low temperature, such as the summer and indoor conditions in Jiangnan and northern regions with high temperature, it is not necessary to select 1.28g/cm as the density value of electrolyte ³ No, the density can be reduced to 1.26g/cm ³ following. The author has done this in Yunnan, and the actual service life of the starting battery has been extended by 50%.
- Startup of dry charged battery
When the battery leaves the factory, the positive plate is full of PbO2 and the negative plate is full of Pb, and some protective measures are taken to keep it in this state stably during storage and transportation. When the user starts the battery, the acid with the specified density is injected into the battery. From the reaction equation, it can be seen that the discharge conditions of the battery have been met, and the battery is in a state that can discharge to the consumer. This battery is called dry charge, Its meaning can be understood as that there is electricity when it is dry and liquid is not injected. Because of saving the energy and time of initial charging, it is more and more popular. Obviously, if the positive and negative plates can maintain their activated state, there is no problem with liquid injection. The objective situation is different from the above: in the process of battery manufacturing, storage and transportation, due to the incomplete protection process, the quality of protective agent, the length of storage and transportation time and the quality of storage environment, it is inevitable that some PB has been converted into PbO when users use it; After acid injection, the following reaction occurs.
It shows that the battery heats up after acid injection. Some manufacturers, due to process problems, have some PbSO4 on the electrode plate when leaving the factory, not all of which are in the activation state of PbO2 and Pb. If users do not have a CB detector that can quickly measure the actual capacity of the battery, they cannot know the dry charge quality of the battery. Many people think that “dry charge” is “100% of the electricity”, which is wrong. Now some manufacturers have made the following instructions in the maintenance procedures: “The electrode plate of this battery is made in a specific way and dried with a special process to ensure that the positive plate contains enough lead dioxide and the negative plate keeps as much velvet lead as possible. The battery assembled with this electrode plate can be kept in a sealed state for a long time, and the battery capacity will not decrease greatly within one or two years. When in use, add electrolyte with specified density, and the motor can be started in a very short time The driving time can be longer. The DC generator on the car can supplement the battery, which is beneficial to the service life of the battery. ” Because the lead dioxide content in the positive plate of commercial batteries has not reached the highest level; There is always a certain amount of lead oxide and lead sulfate in the negative plate, so the first capacity of some dry charge batteries can only reach 30% of the 20h rate, and it is qualified if it reaches 80% according to the national standard.
If the first driving time is very short and the car generator is insufficient to supplement the battery, the lead paste on the positive and negative plates that has not been converted into PbO2 and Pb will be difficult to change again, which will affect the service life of the battery. When the dry battery is used, if conditions permit, it is beneficial to charge it appropriately first, and the amount of charge should be determined according to the state and service conditions of the battery.
The State mentioned here can be judged mainly from whether the density of the injected electrolyte decreases, and the one with no decrease in density is the best. Generally, the density of dry charge battery decreases by 0.02g/cm after adding liquid ³ In order to be normal, the excessive reduction must be supplemented. When the ordinary battery is started, it must be initially charged. Its requirements are detailed in the section of “initial charging”. Now this kind of battery has rarely produced sealed battery. The self discharge of the battery can reduce the battery capacity below the safe capacity. The actual capacity of the storage battery after storage varies with the storage conditions, and it does not have 100% capacity.If you want to know more about batteries click here to open
Read more: What is electrode load analysis for lead-acid batteries?