Battery purchase knowledge

1. Type and introduction

In the electric bicycle market, the most commonly used lead-acid maintenance-free batteries, 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 the 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 the discharge, and the longer the discharge, the thinner the concentration of sulfuric acid. The consumed component is proportional to the discharge capacity. As long as the concentration of sulfuric acid in the electrolyte is measured, that is, the specific gravity is measured, the discharge capacity or residual power can be known. The chemical change during charging is that the lead sulfate produced on the anode plate and the cathode plate 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 for 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 mobile electrolyte. Most of the electric bicycle batteries on the market are AGM 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; its filling volume is 10~15% more than dilute sulfuric acid, and water loss is less, so the gel battery will not be 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, and does not significantly reduce the assembly pressure, 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 can be improved accordingly. Therefore, the over-discharge, recovery capability and low-temperature charge-discharge performance of gel batteries are superior to those of AGM batteries; the consistency of gel batteries is much better than similar AGM batteries. There are four types of colloids that have been mass-produced in China: fumed gel, silica sol, mixed sol, and silicone polymer glue.

The working principle of the lithium ion battery is: when the battery is charged, the lithium in the positive electrode material is released, passes through the diaphragm and enters the negative electrode graphite; when the battery is discharged, the lithium ions are released from the negative electrode graphite and pass through the diaphragm back to the positive electrode material in. As the charge and discharge proceed, lithium ions are continuously inserted and extracted from the positive and negative electrodes.

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 definitely become the second in the future. The winner of the secondary battery. Since its inception in the 1990s, button batteries in electronic products, 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, 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 extremely strong over-discharge resistance and extremely 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. However, due to the different battery material formulations, electrolyte concentration and content of various manufacturers, their charging voltages also have 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 the battery's rated power to avoid long-term battery operation under full or overload conditions.

3. Reasonable use of batteries

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 cause the entire group of batteries to undercharge and prematurely fail. Therefore, on electric bicycles, the uniformity of the battery pack has a considerable impact on the service life of the battery. For consumers, how to use it reasonably will also have a certain impact on the balance and consistency of the battery, thereby affecting the service life of the battery. Based on years of research and actual use of batteries, consumers are advised to use the following methods reasonably.

(1) Electric bike riding speed: 20-25km/h.

(2) Riding distance: 10-30km/day, the depth of discharge is less than or equal to 70% (a deep discharge is performed every 2 months).

(3) Charging frequency: once a day.

(4) Load capacity: single rider (one child under 10 years old can be carried).

According to the above method, a better quality electric bicycle 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, the longer the cycle life of the battery and the longer the battery life cycle. Therefore, consumers generally think that charging once is a cycle is wrong. If you want to extend the life of the battery you use, you must keep the battery in a fully charged state at all times. Under long-term power loss, the negative plate of the battery Easily salted, causing loss of battery capacity and affecting battery life.

Four, battery maintenance

After the qualified batteries for electric bicycles leave the factory, the battery life and performance depend to some extent on the use and maintenance of consumers.

(1) The matching of charger and battery.

The battery for electric bicycles is badly charged, not used. It can be seen the importance of matching the charger and battery. There are two situations: one is that the new charger itself does not match the parameters provided by the battery manufacturer, and the other is charging The quality of the components of the charger itself is poor. When it is first used, it is still matched. As consumers charge and discharge cycles, the charger itself will drift due to temperature rise and component aging, causing the charging voltage and conversion current to drift, and the battery will be damaged. .

(2) Replenish electricity frequently and in time.

Consumers usually have a misunderstanding about the cycle life stated in the instruction manual. They think that the life of the battery will be reduced by one charge, so each time the battery power is consumed to the controller's protection voltage of 31.5V before recharging starts. As everyone knows, this not only can not protect the battery, but also shortens the battery life. Therefore, consumers are reminded to recharge the battery in time when possible.

(3) It is strictly forbidden to continue riding when the indicator shows undervoltage. Some consumers ride on the road halfway, and after the indicator shows the undervoltage condition, they take a break for a while and then ride for a while. This is very harmful to the battery. Serious over-discharge will cause the battery to salt or produce lead. Crystal, short-circuit the battery and affect its life.

(4) The electric booster should be assisted as much as possible just after starting, climbing and overloading.

(5) When riding on rainy days, try to avoid wet switches and connectors to prevent leakage.