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Research on a Lithium Battery Management System and Method

by:dcfpower     2021-03-08
Abstract The lithium battery application management system in this study includes: single-cell lithium battery, lithium battery charge and discharge management module, lithium battery discharge overcurrent protection module, lithium battery voltage overdischarge protection module and lithium battery voltage boost module; use of lithium battery The real-time monitoring technology of charging and discharging current and voltage manages the charging and discharging of lithium batteries and realizes the protection of lithium batteries. [Keywords] charge-discharge over-discharge protection Over-current protection 1 Overview has the characteristics of small size, light weight, large specific energy, long cycle life, low self-discharge rate, no memory effect, green color, and wide operating temperature range. . Lithium batteries are widely used in mobile communication equipment, such as dynamic loop equipment, radio-frequency optical fiber distribution systems, network signal monitors, etc., to monitor the status of these equipment under external power failure; usually the power supply voltage of the equipment monitoring system is 9V or above, the nominal voltage of a single-cell lithium battery is 3.7V. The common solution is to use multiple lithium batteries in series to meet the power supply voltage requirements of the application system, because each battery has certain differences when it leaves the factory As the number of charging and discharging increases, the difference between the lithium batteries in series will become larger and larger, causing the charging time of the batteries in the battery pack to be inconsistent, causing the battery to float, overcharge or overdischarge, and easily cause battery damage.   In order to overcome the shortcomings and shortcomings of lithium battery applications, especially the unbalanced charging and discharging problems of multiple lithium batteries in series, the use of management systems and technical solutions based on single-cell lithium battery applications can effectively solve these inherent defects.  2 charge and discharge management requirements    overcharge, overdischarge, overcurrent, high temperature, low temperature use, etc. may cause physical and chemical damage to the lithium battery. The ideal charging process of lithium battery: pre-charge, constant current charging, constant voltage charging, trickle charging, charging is completed, continuously monitor the voltage of the lithium battery and compare it with the threshold, if it is low, restart the charging. After the lithium battery is fully charged, try to avoid floating Charge.  The ideal lithium battery charging voltage and current curve is shown in Figure 1. u003cpu003eu003c/pu003e  3 Block diagram of a single-cell lithium battery management system  The nominal voltage of a single-cell lithium battery is usually 3.7V, which is usually difficult to meet the power supply requirements of the equipment monitoring system.   Single-cell lithium battery charge and discharge management system includes: lithium battery charge and discharge management module, lithium battery discharge overcurrent protection module, lithium battery voltage overdischarge protection module and lithium battery voltage boost module. The system principle block diagram is shown as in Fig. 2. The input part of the lithium battery management system is the external charging power supply, and the output part is the working power supply of the application system. The lithium battery charge and discharge management module, the lithium battery voltage overdischarge protection module, and the lithium battery discharge overcurrent protection module are only logically divided, and the physical May be integrated. 4 The charging and discharging management method of a single-cell lithium battery is based on the typical charging voltage and current curve of the lithium battery, combined with the characteristics of the lithium battery in the mobile communication device. When the external power supply of the application system is powered off, the lithium battery management system can seamlessly switch the application system power to Using lithium battery power supply, when the lithium battery is discharged, it can timely monitor the lithium battery overcurrent and overdischarge and automatically cut off; when the external power supply of the application system is normal, the lithium battery can be charged in time according to the detected voltage of the lithium battery to avoid Floating charge and so on. The charging and discharging management process of a single lithium battery is as follows. (1) When the external charging power supply is normal and the lithium battery is not fully charged, the lithium battery charging and discharging management module monitors the voltage of the lithium battery and the voltage of the external charging power supply. When the voltage of the lithium battery is lower than When the lithium battery charging voltage threshold, the lithium battery charging process is started. When it is monitored that the lithium battery voltage is equal to the maximum voltage of the lithium battery, and the charging current is very small, the lithium battery charging process is stopped to avoid floating charging;    (2) Power supply from an external charging power supply Under normal conditions, and when the lithium battery is fully charged, the lithium battery charge and discharge management system continuously monitors the voltage of the lithium battery and the voltage of the external charging power supply. If the voltage of the lithium battery is lower than the lithium battery charging voltage threshold, it will restart Start the lithium battery charging process;    (3) In the case of abnormal external charging power supply, the lithium battery charging and discharging management system monitors the voltage of the lithium battery pack and the voltage of the external charging power supply. At this time, the voltage of the external charging power supply module is detected to be abnormal. The lithium battery discharge process is started;    (4) The lithium battery discharge overcurrent protection module always monitors the working current in the lithium battery discharge circuit, and when it detects that the lithium battery discharge current in the discharge circuit is greater than the maximum discharge current threshold of the lithium battery, it shuts down Open the lithium battery discharge circuit; when it is monitored that the lithium battery discharge current in the discharge circuit is lower than the maximum discharge current threshold of the lithium battery, the lithium battery discharge circuit is reopened; and so on. (5) The lithium battery voltage over-discharge protection module always monitors the current voltage of the lithium battery. When the voltage of the lithium battery is lower than the minimum discharge voltage threshold, it disconnects the lithium battery discharge circuit and stops the lithium battery power supply; when the lithium battery voltage is monitored When the voltage is higher than the minimum voltage threshold, the lithium battery discharge circuit is reopened; and so on.   The lithium battery voltage boost module boosts the voltage of a single cell lithium battery to a voltage value suitable for the operation of the application system to meet the voltage requirements of the application system. 
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