What is the lower limit standard of lead acid battery discharge? Next, we will introduce the lower discharge limit standard of lead acid battery in detail.
The positive and negative plates of the discharged battery are all PbSO4. Because the same substance can only show the same potential in the sulfuric acid electrolyte, there is no power for electron transfer between them, so the voltage of the discharged battery decline. If the electrode plate of the battery is as shown in Figure 1-1, there is only one PbO2 molecule on the positive electrode, only one Pb molecule on the negative electrode, and only two H2SO4 molecules in the electrolyte.
Figure 1-1 Lead acid battery charge and discharge
When two electrons on the negative plate are transferred to the positive electrode, the terminal voltage of the battery will undoubtedly drop to zero. However, in the lead-acid batteries used by real teachers, the active materials on the positive and negative plates have a large amount of excess, and the utilization rate of lead is only about 50%. Therefore, there are still a considerable amount of positive plates on the discharged positive plates. For PbO2, there is also a considerable amount of Pb on the negative electrode. It is not only PbSO4 as shown in Figure 1-1. Of course, these two substances still have a tendency to discharge electrons. Therefore, when the battery discharges its specified capacity, its terminal voltage drops slightly, not to zero.
In daily work, the lead acid battery is not allowed to be discharged without measuring the voltage with a multimeter. If it exceeds the limit specified in the battery instruction manual, it will become difficult to recharge, and because the depth of discharge is too large, the active material on the electrode plate is easy to fall off. , Which is very harmful to battery life. If there is no special discharge device, just simply use a bulb or resistor to discharge, do not adjust the discharge current, and do not monitor the battery terminal voltage, the worker does not even know the technical requirements of the lower limit of the effective battery power, the discharge level should be Stop, only to see that the discharge bulb does not light up, then stop the discharge. Such discharging operation makes it difficult to recover the active material, which is harmful and useless. The basic structure of the discharge equipment is shown in Figure 1-2
Figure 1-2 Basic structure of discharge equipment
International standards stipulate that car batteries are discharged at a constant current rate of 20h. For example, a 100A.h battery is discharged with 100/20=5 (A). When the terminal voltage of a 12V battery drops to 10.5V, the discharge stops. The detection of car start-up batteries is usually to compress the working time, usually 10h rate or 5h rate discharge, the conversion ratio of the two is 0.93C20=C10, 0.9C10=C5.
Principle and maintenance of lead acid battery,You can learn more about lead acid battery.