1. Type and introduction
In the electric bicycle market (Rialto), the most commonly used is lead-acid maintenance-freeAccumulator, There are AGM-type batteries that use glass fiber separator adsorption technology, and GEL-type gel batteries that use colloidal electrolyte technology.
The working principle of the lead battery is that the anode (PbO2) and the cathode (Pb) in the lead battery are immersed in the electrolyte (dilute sulfuric acid), and 2V electricity is generated between the two electrodes. The chemical change in the discharge is that dilute sulfuric acid will react with the active materials on the anode and cathode plates to form a new compound "lead sulfate". The sulfuric acid component is released from the electrolyte through discharge, and the longer the discharge, the thinner the concentration of sulfuric acid. The consumed component is proportional to the discharge amount. As long as the concentration of sulfuric acid in the electrolyte is measured, that is, the specific gravity is measured, the discharge amount or residual electricity can be known. The chemical change during charging is that the lead sulfate produced on the anode plate and the cathode plate during discharging will be decomposed and reduced to sulfuric acid, lead and lead peroxide during charging. Therefore, the concentration of the electrolyte in the battery gradually increases, that is, the electrolyte. The specific gravity rises and gradually returns 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 powered again. When the lead sulfate at the two poles is reduced to the original active material, it is equal to the end of charging. , While the cathode plate produces hydrogen, and the anode plate produces oxygen. At the final stage of charging, the current is almost used in the electrolysis of water, so the electrolyte will be reduced. At this time, pure water should be used to supplement it.
The AGM battery is filled with dilute sulfuric acid. The dilute sulfuric acid is absorbed in the ultra-fine glass fiber separators and plates, and there is almost no flowing electrolyte. At present, most of the electric bicycle batteries sold on the market (Rialto) are AGM-type batteries.
The GEL type gel battery has no free electrolyte after the electrolyte gel, and the probability of acid leakage is much smaller than that of the previous battery. Loss of water causes failure; the infusion of colloid increases the strength of the separator, protects the plates, makes up for the defect of the separator contracting with acid, so that the assembly pressure is not significantly reduced, which is one of the reasons for its prolonged battery life; colloid filling The gap between the separator and the electrode plate is reduced, the internal resistance of the battery is reduced, and the charge acceptance ability can be improved accordingly. Therefore, the over-discharge, recovery capability and low-temperature charge-discharge performance of the gel battery are superior to those of the AGM battery; the consistency of the gel battery is much better than that of the similar AGM battery. There are four types of colloids that have been mass-produced in China: fumed glue, silica sol, mixed sol, and silicone polymer glue.
The working principle of lithium-ion battery is: when the battery is charged, the lithium in the positive electrode material is released, passes through the diaphragm and enters into the negative electrode graphite; when the battery is discharged, the lithium ions are released from the negative electrode graphite and pass through the diaphragm to return to the positive electrode material. middle. With the progress of charge and discharge, lithium ions are continuously inserted and extracted from the positive electrode and the negative electrode.
Lithium-ion battery is a kind of secondary battery. Because it has many advantages such as high energy density, high current charge and discharge, no memory effect, low raw material cost, and environmental friendliness, its sales volume has increased rapidly year by year after its introduction, and it will surely become the second battery in the future. The winner of the secondary battery. Since its inception in the 1990s, button batteries in electronic products and lithium batteries in mobile phones and DC digital products have also been applied to electric bicycles. However, the cost of lithium-ion batteries accounts for one-third to one-half of the cost of electric vehicles, which is far greater than the proportion of lead-acid batteries in the entire vehicle. And because lithium batteries have high specific energy and poor material stability, lithium batteries are prone to safety problems. With the development of technology, mature lithium-ion batteries will become the development trend of high-quality electric vehicles.
Second, the key points of battery purchase
AGM battery has the advantages of low cost and large discharge current, but it has the defects of narrow operating temperature range, battery loss of water and thermal runaway; while GEL battery has high cost, but it has stable performance, wide operating temperature range, and over-endurance. Advantages such as over-discharge and long life.
Since electric bicycle batteries are high-current, deep-cycle discharge in most cases, gel batteries are more suitable for electric bicycle batteries. Gel batteries have strong over-discharge resistance and strong electro-hydraulic storage capacity, which avoids the impact of over-discharge on the battery and the occurrence of thermal runaway due to battery loss.
The charging characteristics of various brands of lead-acid batteries are basically the same, but because the battery material formula, electrolyte concentration and content of each manufacturer are different, their charging voltage also has certain differences. Therefore, strictly speaking, it should be based on each battery manufacturer. The specific requirements are given to determine the charging voltage scheme of the battery, otherwise it is easy to cause improper use of the battery.
The output power of the electric bicycle motor must match the battery's rated power. Therefore, in order to prolong the battery's service life, the electric bicycle's motor power should be as small as possible than the battery's rated power to prevent the battery from working under full or overload conditions for a long time.
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