| The paper devoted to design a household standby power supply, the Li-ion battery pack could be charged by city electricity at night when the electricity price is low, user could use standby power supply when blackout occur or city electricity could not meet the requirement. This system use Li-ion battery pack as storage of electric energy, we can achieve high voltage and capacity by this way, but also exist many problems, for examples, overcharge and over discharge of single cell as well as over temperature and over current, the matching of single cell, etc. We design this system to solve above problems to guarantee the standby power supply can run safely, reliably, stably.The system select PIC24FJ64GA106 Micro controller of Microchip company as control unit, complete voltage acquisition of each node of Li-ion battery pack by A/D converter of Micro controller, calculate the voltage of 16 single cell, compare the voltage of single cell with threshold voltage, control the charge and discharge process according to compare result. In order to avoid over temperature and over current phenomenon, use digital temperature sensor DS18B20 to complete temperature acquisition of 16 single cell, use Holzer current sensor to complete current acquisition of Li-ion battery pack, when temperature or current meet threshold, stop the charge and discharge process and start Acousto-optic alarm. Micro controller can send the voltage data of charge and discharge process of all single cell to PC, user can analysis the data and eliminate the single cell that performance is bad from Li-ion battery pack. In order to prolong service life of Li-ion battery pack, we design charge equalization circuit based on study of principle and characteristics of Li-ion battery pack. The experimental results show that system could work stably, after adding a charge equalization circuit, ensure all single cell could meet high threshold voltage, the performance of Li-ion battery pack is improved. |
PDF Full Text Request