Since 1859, lead-acid batteries have been the most widely used products in the battery field, such as automobiles, locomotives and ships. There are lead-acid batteries on airplanes and backup power equipment, and lead-acid batteries are well received in these areas. But why are there complaints about using the same products on electric bicycles? It is generally reported that the life span is too short. Why is this? Next, we analyze the reasons that affect the life of lead-acid batteries from various aspects;

1. Life failure caused by the working principle of lead-acid batteries;

The charging and discharging process of lead-acid batteries is an electrochemical reaction process. When charging, lead sulfate forms lead oxide, and when discharging, lead oxide is reduced to lead sulfate. Lead sulfate is a very easy to crystallize substance. When the concentration of lead sulfate in the battery electrolyte is too high or the static idle time is too long, it will gather together to form small crystals. These small crystals attract the surrounding sulfuric acid. Lead is like a snowball, forming large inert crystals. The crystalline lead sulfate can no longer be reduced to lead oxide when charged, but will precipitate and adhere to the electrode plate, resulting in a reduction in the working area of ​​the electrode plate. This phenomenon is called vulcanization. Also called aging. At this time, the battery capacity will gradually decrease until it becomes unusable. When a large amount of lead sulfate accumulates, it will attract lead particles to form lead branches. The bridging between the positive and negative plates will cause the battery to short circuit. If there are gaps on the surface of the electrode plate or the sealed plastic box, lead sulfate crystals will accumulate in these gaps, and expansion tension will occur, which will eventually cause the electrode plate to break or the shell to break, resulting in irreparable consequences. The battery is physically damaged. Therefore, an important mechanism leading to the failure and damage of lead-acid batteries is the vulcanization that cannot be prevented by the battery itself.

2. Reasons for the special working environment of electric bicycles

As long as it is a battery, it will be vulcanized during use, but lead-acid batteries in other fields have a longer life than electric bicycles. This is because the lead-acid battery of an electric bicycle has a working environment that is prone to vulcanization.

①Deep discharge
The battery used in the car only discharges in one direction during ignition. After ignition, the generator will automatically charge the battery without causing deep battery discharge. However, it is impossible to charge an electric bicycle while riding, and it often exceeds 60% of the deep discharge. During the deep discharge, the concentration of lead sulfate increases, and the vulcanization will be very serious.

②High current discharge
The cruising current of an electric bicycle for 20 kilometers is usually 4A, which is already higher than its value. The working current of the battery in other areas, as well as the working current of overspeed and overload electric bicycles is even greater. Battery manufacturers have conducted cycle life tests of 70% at 1C and 60% at 2C. After such a life test, many batteries have a lifespan of 350 charge and discharge cycles, but the actual effect is quite different. This is because high current operation will increase the depth of discharge by 50%, and the battery will accelerate vulcanization. Therefore, because the body of the three-wheeled motorcycle is too heavy and the working current is greater than 6A, the battery life of the electric three-wheeled motorcycle is short.

③High frequency charging and discharging
The battery used in the field of backup power will only be discharged after the power is cut off. If the power is cut off 8 times a year, it will reach a 10-year life span and only need to be recharged 80 times. Lifetime, it is common for electric bicycle batteries to charge and discharge more than 300 times a year.

④Short-term charging
Since electric bicycles are a means of transportation, there is not much charging time. In order to complete the 36V or 48V 20A hour charging within 8 hours, when the charging voltage exceeds the oxygen evolution voltage of the cell (2.35V), it is necessary to increase the charging voltage (usually 2.7~2.9V for the cell). Or when the hydrogen release voltage (2.42 volts), due to the release of too much oxygen, the battery will open the exhaust valve, which will cause the loss of water and increase the concentration of the electrolyte, and increase the vulcanization of the battery.

⑤Can not be charged in time after discharge
As a means of transportation, the charging and discharging of electric bicycles are completely separated. When charged and reduced to lead oxide, it will sulfide and form crystals.

3. Reasons for battery production
In view of the particularity of lead-acid batteries for electric bicycles, many battery manufacturers have adopted a variety of methods. The most typical method is as follows:

① Increase the number of boards.
Change the original design of a single grid of 5 blocks and 6 blocks to 6 blocks and 7 blocks, 7 blocks and 8 blocks, or even 8 blocks and 9 blocks. By reducing the thickness of the electrode plates and separators, and increasing the number of electrode plates, the battery capacity can be increased.

② Increase the proportion of sulfuric acid in the battery.
The sulfuric acid specific gravity of the original floating battery is usually between 1.21 and 1.28, while the sulfuric acid specific gravity of the electric bicycle battery is usually between 1.36 and 1.38, which can provide more current and increase the initial current. battery capacity.

③The amount and ratio of lead oxide newly added as a positive electrode active material.
The addition of lead oxide increases the new electrochemical reaction substances involved in the discharge, which also newly increases the discharge time and increases the battery capacity.