- Electromotive force of lead-acid battery
The terminal voltage (ie open circuit voltage) measured in the lead-acid battery under no load state can be regarded as the value of the battery electromotive force. The electromotive force of the lead-acid battery is different from the terminal voltage. The electromotive force of the lead-acid battery is the open-circuit voltage, and the terminal voltage is the closed-circuit voltage. The relationship between the electromotive force of the battery and the density of sulfuric acid is shown in Figure 1. It can be seen from the figure that when the density of sulfuric acid increases (when the density of sulfuric acid is in the range of 1.05~1.300g/cm3), the value of the electromotive force of the battery increases accordingly, which is a linear relationship. Temperature has little effect on the electromotive force of lead-acid batteries. In addition to lead batteries, lithium batteries are also very good options, if you are interested, please visit Tycorun Lithium Battery.
People often say: This battery voltage is 12V. The 12V mentioned here refers to the most basic parameter of the battery – the nominal potential (unit V). The nominal potential of a lead-acid battery cell is 2V, and the nominal potential of a battery with 6 cells connected in series is 12V. 2 to 5 12V batteries are connected in series to form 24V, 36V, 48V, 60V battery packs, all of which refer to the nominal potential of the battery pack, which is a theoretical value determined by the characteristics of the active material used in the battery.
In fact, there are differences in the voltage and nominal potential of the battery under different conditions. For example: a normal lead-acid battery with a nominal potential of 12V, at the end of the charging process, the charging polarization reaches the maximum value, and the voltage can reach 14.4V or higher; at the end of the discharge, the discharge polarization reaches the maximum value, The voltage can be as low as around 9V. After charging or discharging is stopped and left standing for several hours, the polarization voltage (concentration polarization) disappears completely, and the potential of this 12V battery can be between 13.8V (after full) and 11V (after discharge). The difference is caused by a change in the state of the active material inside the battery.
- Power and efficiency
The power and efficiency of a lead-acid battery are the amount of energy it can output per unit time under certain discharge conditions. Power is a very important feature of lead-acid batteries, because the greater the power of a lead-acid battery, the more the battery is discharged at a relatively large current. Here we discuss the efficiency of lead-acid batteries from the perspective of energy efficiency. The efficiency of lead-acid batteries is expressed by the following formula: η=W (discharge)/(charge) × 100%
- Internal resistance of lead-acid batteries
The resistance exhibited by the lead-acid battery when it is discharged is the internal resistance of the lead-acid battery. The internal resistance of lead-acid batteries is related to the following factors.
①The larger the area of the plate, the smaller the distance between the positive and negative plates, and the smaller the internal resistance.
② After the lead-acid battery is charged, the internal resistance becomes smaller, and after discharge, the internal resistance becomes larger. This is because the density of the electrolyte in the pores of the plate decreases during discharge, and the internal resistance increases after discharge, especially as the discharge time increases, the effective substance becomes lead sulfate at the end of the discharge. Lead sulfate becomes a poor conductor, so with the increase of lead sulfate, the internal resistance gradually increases.
③ The influence of temperature on the internal resistance of lead-acid batteries is also relatively obvious. When the temperature of the lead-acid battery drops, the electrical conductivity drops and the internal resistance increases.
- Failure causes and repair methods of lead-acid batteries
The current best way to store electricity from solar cells is with lead-acid batteries. Because lead-acid batteries have many excellent properties, especially the characteristics of large capacity and high current discharge, they cannot be replaced by other batteries for the time being. However, lead is poisonous, expensive, and has a short service life. These outstanding problems have not yet been well resolved. If the cause of the failure of the lead-acid battery can be found, the service life of the lead-acid battery can be prolonged, so that the cost can be relatively reduced, and it is also conducive to environmental protection.
Read more: What are the performance parameters of solar cells?
