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The technical way to realize battery fast charging Guangzhou Battery Factory
Guangzhou Battery Factory
1. Improve battery design to reduce ohmic resistance
According to the fast charging target specified by ALABC, if a 100Ah starting lead battery is required to charge the battery capacity from 20% to 50% within 5 minutes, that is, the charged power is 100×(0.5-0.2)u003d30Ah, then charge The current should not be less than 30÷(5÷60)u003d360A, which is 3.6(A). At this time, the battery ohm drop is 360×6×u003d0.216V, and the battery voltage reaches 1.97＋0.216＋0.030＋0.006＝2.23V. When the gassing voltage is reached, the battery can be safely charged. The horizontal sealed lead battery has a lower ohmic resistance, a 112Ah single cell battery is 0.3mΩ, and the battery capacity is charged from 20% to 50% within 5 minutes. The charging current is 112×(0.5-0.2)÷(5÷60)u003d403A , The ohmic drop of the battery when charged with this current is 403×3×u003d0.121V, which is lower than the starting battery. Obviously, the horizontal sealed lead battery can be charged with more power when it is charged to the gassing voltage, that is, its fast charging performance is better.
Our previous work has been obtained. If the lead-acid battery adopts a copper-drawn negative grid, it will significantly reduce the board resistance; this will not only help improve the utilization of active materials Compared with battery power, it also improves battery fast charging performance. It seems that the use of lead-acid batteries with a negative grid of copper meshes will bring great benefits to electric vehicles.
2. Increase the diffusion rate of reactive ions
This is to increase the diffusion current density of lead-acid batteries, which is to delay the battery In the charging process, the time when the limit diffusion current appears, that is, the time for the battery voltage to reach the gassing voltage is delayed, thereby allowing the charging current to be increased and rapid charging.
reduce the thickness of the electrode plate, increase the porosity of the active material, and increase the contact area between the grid and the active material. These measures are all conducive to the diffusion process of reactants and products. The concentration polarization is reduced, the allowable charging current value is increased, and rapid charging is realized. However, considering battery life, the plates cannot be made too thin.
3. Reform the battery charging method
The theoretical basis of the pulse fast charging method is to superimpose a certain amount in the charging current. Negative pulses of frequency, width and height or short-time stop charging can make the ions participating in the reaction have time to generate and increase their concentration, and make the generated and ions have time to move away from the electrode surface. The overall effect is to reduce the concentration. Polarization allows to increase the charging current and shorten the charging time.
It should be pointed out that the terminal voltage of a lead battery is constantly increasing during the charging process, that is to say, the polarization distribution of the battery is different at different charging stages, so When designing a pulse charging device, the charging current and time should be automatically adjusted according to the allowable voltage value when the battery is charged; at the same time, the width and height of the negative pulse must be automatically adjusted according to the battery voltage drop value during the negative pulse discharge process. In this way, although the charging current is very large, due to the timely and effective measures to reduce the concentration polarization, the battery voltage rises slowly, so that the battery is charged with more power. The intelligent charging device currently developed is designed after taking these conditions into account.
4. The impact of fast charging on battery life
Is the impact of high current fast charging on battery life good or bad? There are different opinions; it is not surprising that such a different view appears. This is firstly due to the fact that the battery life is not consistent. In our experiments, it has been observed that even a batch of batteries prepared at the same time from the production line can have a cycle life that is even twice as different. Furthermore, during a long-term life test. , It is difficult to ensure that the test conditions of each batch of batteries are completely consistent. Although it is generally believed that high-current charging will shorten the battery life, it has been reported in the literature that with proper cooling, the cycle life of valve-regulated sealed lead batteries has been improved due to high-current charging.
Our experiments show that under the condition of keeping the battery charging voltage lower than the gassing voltage, high-current fast charging does not adversely affect the battery life. In the process of using the electric vehicle battery, it is not necessary to charge to 100% of the rated capacity every time, but the battery should be fully charged every other week (preferably not more than half a month). Especially when the electric vehicle is not in use, the battery should be fully charged and stored. This will help extend the life of the battery.
(1) Lead-acid batteries are cheap and have a long life. The batteries themselves are constantly updated and developed. Therefore, it is still a viable power source for electric vehicles in the near future.
(2) The ohmic internal resistance of the battery is the main factor that causes the battery voltage to rise during high-current charging; the battery structure must be improved to reduce the internal resistance to meet the rapid response of electric vehicles to the battery Requirements for charging.
(3) The use of pulse charging and intelligent charging devices is beneficial to reduce concentration polarization and improve charging efficiency.
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