Common two-lithium-ion battery pack charging method analysis

　　Author ：Iflowpower – Portable Power Station Supplier

With the rapid development of society, our lithium-ion batteries are also developing rapidly. So you understand the detailed information of lithium-ion batteries? Next, let Xiaobian lead everyone to learn more about knowledge. Lithium-ion battery is an ideal power supply due to high operating voltage, small size, light quality, no memory effect, no pollution, self-discharge, long cycle life is an ideal power supply.

In actual use, in order to obtain a higher discharge voltage, at least two monomer lithium ion batteries are generally used in series to use a lithium ion battery pack. At present, the lithium-ion battery pack has been widely used in a variety of fields such as laptops, electric bicycles and spare power. Therefore, how to use the lithium ion battery pack when charging is particularly critical, and several charging methods commonly used in lithium ion battery packs and the most suitable charging method believed are as follows: 1 Ordinary series charge, current, lithium ions The charging of the battery pack is generally charged in series, which is important because the series charge method is simple, the cost is low and easy to implement.

However, due to the difference in capacity, internal resistance, attenuation characteristics, self-discharge between single-cell-based cells, when charging the lithium ion battery pack, the cell is smaller than the battery in a single-cell battery cell. It will be fully charged, at this time, other batteries have not been filled with electricity, if you continue to charge the charge, the charged single lithium ion battery may overcharge. Excessive charging of lithium-ion batteries will seriously damage the performance of the battery, and may even cause explosion, resulting in personal injury.

Therefore, in order to prevent excessive charging of a single lithium ion battery, it is usually provided with a battery management system (BatteryManagementSystem, abbreviated as BMS), and each single lithium ion battery is overcharged by battery management system. When charging is charged, if the voltage of a single lithium ion battery reaches overcharge protection voltage, the battery management system cuts off the entire charging circuit and stop charging to prevent individual batteries from overcharge, resulting in other battery charging. Lithium-ion battery cannot be fully charged.

After years of development, lithium iron phosphate dynamic lithium-ion batteries have basically satisfied the requirements of electric vehicles, especially pure electric vehicles due to high safety and good cycle performance. This process is basically available for mass production. However, the performance of the lithium iron phosphate ion battery is different from other lithium ion batteries, especially its voltage characteristics and lithium-manganese acid lithium-ion batteries.

In addition, although some battery management systems have equalization function, due to cost, heat dissipation, reliability, etc., the balanced current of the battery management system is often much smaller than the current charged current, so the equalization effect is not very good. Obvious, it will appear.

Some single-section batteries are not fully charged, which is especially obvious about the lithium-ion battery pack to be high current charging, such as the lithium ion battery pack of electric vehicles. 2 Battery management system and charging machine coordination with series charge battery management system is the most fully understood device for battery performance and state. Therefore, by establishing a connection between the battery management system and the charger, the charger can understand the battery information in real time, thereby solving the battery charging time more effectively.

The principle of battery management system and charger coordinated charging mode is: battery management system monitors the current state of the battery (such as temperature, single battery voltage, battery operating current, consistency and temperature rise, etc.). And use these parameters to estimate the maximum allowable charging current of the current battery; during charging, battery management systems and chargers are connected by communication lines, and implement data sharing.

The battery management system will increase the total voltage, the maximum single battery voltage, the maximum temperature, the maximum allowable charging voltage, the maximum allowable single battery voltage and maximum allowable charging current to the charger, the charger can be managed according to the connection to battery management The information supplied by the system will change its own charging strategy and output current. When the maximum allowable charging current supplied by the battery management system is higher than the design current capacity of the charger, the charger will be charged according to the maximum output current of the design; when the battery voltage and temperature exceeds the limit, the battery management system can detect in real time and Timely notify charging. When the charging current is greater than the maximum allowable charging current, the charger begins to follow the maximum allowable charging current, effectively prevent the battery from overcharge, reaching the purpose of extending battery life.

Once the failure is in the charging process, the battery management system can set the maximum allowable charging current to 0, so that the charger will stop running, thereby preventing an accident and ensuring the safety of charging.