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Battery purchasing knowledge

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Battery purchasing knowledge
1、 Type and introduction
In the electric bicycle market, the most commonly used batteries are lead-acid maintenance free batteries, AGM batteries using glass fiber partition adsorption technology, and GEL gel batteries using gel electrolyte technology.
The working principle of the lead battery is that the anode (PbO2) and cathode (Pb) in the lead battery are immersed in the electrolyte (dilute sulfuric acid), and 2V power will be generated between the two poles. The chemical change in the discharge is that dilute sulfuric acid will react with the active substances on the cathode and anode plates to form a new compound "lead sulfate". The sulfuric acid component is released from the electrolyte through discharge. The longer the discharge, the thinner the sulfuric acid concentration. The components consumed are proportional to the discharge capacity. As long as the concentration of sulfuric acid in the electrolyte is measured, that is, its specific gravity, the discharge capacity or residual capacity can be known. The chemical change during charging is that the lead sulfate generated on the anode plate and cathode plate during discharge will be decomposed and reduced to sulfuric acid, lead and lead peroxide during charging, so the concentration of electrolyte in the battery will gradually increase, that is, the proportion of electrolyte will increase, and gradually return to the concentration before discharge. This change shows that the active substance in the battery has been reduced to the state that it can be powered again, When the lead sulfate at the two poles is reduced to the original active substance, it is equal to the end of the charging, while the cathode plate generates hydrogen and the anode plate generates oxygen. When the charging reaches the final stage, the current is almost used for the electrolysis of water, so the electrolyte will be reduced. At this time, pure water should be added.
AGM battery is filled with dilute sulfuric acid, which is absorbed in ultra-fine glass fiber separator and plate, and there is almost no flowing electrolyte. Most of the electric bicycle batteries sold on the market are AGM batteries.
GEL gel battery has no free electrolyte after the electrolyte gel, so the probability of acid leakage is much lower than that of the previous battery; Its perfusion amount is 10~15% more than that of dilute sulfuric acid, and water loss is less, so the gel battery will not fail due to water loss; The filling of colloid increases the strength of the separator, protects the electrode plate, makes up for the defect of the separator shrinking when it meets the acid, and does not significantly reduce the assembly pressure, which is one of the reasons why it can prolong the battery life; The colloid fills the gap between the separator and the electrode plate, reducing the internal resistance of the battery, and improving the charging acceptance. Therefore, the overdischarge, recovery capacity and low temperature charge discharge performance of gel battery are superior to AGM battery; The consistency of gel battery is much better than that of similar AGM battery. There are four kinds of colloids that have been mass produced in China: vapor phase adhesive, silica sol, aerosol, and silicone polymer adhesive.
The working principle of lithium-ion battery is: when the battery is charged, the lithium in the positive electrode material will come out and enter the negative electrode graphite through the diaphragm; When the battery is discharged, lithium ions will be separated from the negative graphite and returned to the positive material through the diaphragm. With the charging and discharging process, lithium ions are constantly embedded and removed from the positive and negative electrodes.
Lithium ion battery is a kind of secondary battery. Due to its high energy density, large current charging and discharging, no memory effect, low raw material cost, environment-friendly and many other advantages, its sales volume has increased rapidly year by year since its introduction, and it will become a winner in the secondary battery in the future. Since its appearance in the 1990s, button batteries in electronic products and lithium batteries in mobile phones and DC digital products have also been used in electric bicycles. However, the cost of lithium-ion batteries accounts for one-third to one-half of the cost of electric vehicles, far more than the proportion of lead-acid batteries in the vehicle. Moreover, due to the high specific energy and poor material stability, lithium batteries are prone to safety problems. With the development of technology, lithium-ion batteries will become the development trend of high-quality electric vehicles.
2、 Key points of battery selection
AGM battery has the advantages of low cost and large discharge current, but it has the defects of narrow working temperature range, easy loss of water and thermal runaway; GEL battery has high cost, but it has the advantages of stable performance, wide operating temperature range, over charging and over discharging resistance, long life, etc.
As the electric bicycle battery is subject to high current and deep cycle discharge in most cases, the electric bicycle battery is more suitable for colloid battery. Colloid battery has strong over discharge resistance and strong electrohydraulic storage capacity, which avoids the impact of over discharge on the battery and thermal runaway caused by battery water loss.
The charging characteristics of various brands of lead-acid batteries are basically the same. However, due to the different battery material formulations, electrolyte concentrations and contents of different manufacturers, their charging voltages are also different. Therefore, strictly speaking, the charging voltage scheme of the battery should be determined according to the specific requirements given by the battery manufacturers, otherwise it is easy to cause improper use of the battery.
The output power of the electric bicycle motor should match the rated power of the battery. Therefore, in order to prolong the service life of the battery, the motor power of the electric bicycle should be less than the rated power of the battery as much as possible to avoid the battery working under full load or overload conditions for a long time.
3、 Reasonable use of battery
When the batteries are used in series, if the internal resistance of the batteries is inconsistent, the battery terminal voltage will be inconsistent during the charging and discharging process, which will eventually lead to the under charging of the whole battery group and premature failure. Therefore, on the electric bicycle, the balance and consistency of the battery pack have a considerable impact on the service life of the battery. For consumers, how to use them properly will also affect the balance and consistency of the battery, thus affecting the service life of the battery. According to the research and actual use of batteries for many years, consumers are suggested to use batteries in the following ways.
(1) Riding speed of electric vehicle: 20-25km/h.
(2) Riding distance: 10-30km/day, discharge depth ≤ 70% (deep discharge once every 2 months).
(3) Charging frequency: once a day.
(4) Load capacity: single ride (one child under 10 years old can be carried).
According to the above method, the electric bicycle with good quality can be used for 3-4 years, even 5 years, and the battery can be used for about 1.5 years. The shallower the battery discharge depth is, the longer the battery cycle life is, and the longer the battery life is. Therefore, consumers generally believe that charging once is a cycle is wrong. In order to prolong the life of the battery they use, they must always keep the battery in a fully charged state. In a long time of power loss, the negative plate of the battery is prone to salinization, causing loss of battery capacity and affecting the service life of the battery.
4、 Battery maintenance
The service life and performance of qualified electric bicycle batteries after leaving the factory by the battery manufacturer depend to some extent on the use and maintenance of consumers.
(1) Matching of charger and battery.
The battery for electric bicycle is charged and not worn out, which shows the importance of matching the charger and battery. There are two cases: first, the parameters provided by the new charger itself and the battery manufacturer do not match, and second, the components of the charger itself are poor in quality. At the beginning of use, the battery is still matched. As consumers charge and discharge repeatedly, the charger itself is aging due to temperature rise, As a result, the charging voltage and switching current drift and the battery is damaged.
(2) Make up electricity regularly and timely.
Consumers often have a misconception about the cycle service life specified in the user manual. They think that once charged, the battery life will be reduced once. Therefore, they wait until the battery power is consumed to 31.5V of the protective voltage of the controller before they start to recharge. However, they do not know that this will not only protect the battery, but also shorten the battery life. Therefore, consumers should be reminded to replenish the battery in a timely manner when possible.
(3) It is forbidden to continue riding when the indicator shows undervoltage. Some consumers ride on the road. After the indicator shows the undervoltage condition, they take a break and then ride for a while. This will do great harm to the battery. Severe overdischarge will salinize the battery or generate lead dendrites, short circuit the battery and affect its life.
(4) The electric power assisted vehicle shall be assisted as far as possible when it is just started, when it is climbing and when it is overloaded.
(5) When riding in rainy days, try to avoid the switch and connector getting wet to prevent electric leakage.

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