A shallow of self-discharge detection circuit design

Source: 2020 - 04 - 14 about clicks occurred: a self-discharge detection circuit design self-discharge is caused by the battery internal factors, not caused by external factors. In general, the self-discharge of the battery performance is by positive and negative electrodes, battery separator, and the performance of the electrolyte, and the influence of manufacturing process and production requirements. The size of the self-discharge, however, is not fixed to the battery life, is also the battery aging degree, and the temperature of the battery SOC environment, etc. , and bad charging and discharging system and working conditions may also affect the self-discharge of the battery. In addition to the production process and the use of improper way of self-discharge, factors that affect the battery self-discharge only temperature and battery life, battery charged state. Among them, the influence of temperature on the battery self-discharge obviously. The higher the temperature, battery's internal chemical reaction, the more active, lead to the battery self-discharge of the chemical reaction with the increase of temperature and speed. Therefore, the higher the temperature, the greater the battery self-discharge rate. The battery storage and use process, should keep the battery in low temperature range, the rise of temperature of the outside in order to avoid the battery or the battery itself and increase the self-discharge, bring down the battery performance. SOC battery charging status. Cells in different charged state, self-discharge size is also different. In general, the greater the charged state of lithium battery, self-discharge phenomenon is more obvious. Life said the aging degree of the battery. With continuous aging cells, continues to increase its internal resistance of battery charge ability. Our common battery standby time more and more short, aging is due to the battery, in the process, in addition to the internal polarization phenomenon seriously, self-discharge has increased. Self-discharge detection circuit is the core of self-discharge test method. According to the capacity of conservation method, it is necessary to monitoring and maintaining the battery charged state or voltage power required. Therefore, it is necessary for battery charge and discharge in the self-discharge detection circuit control circuit, to detect voltage stability when the charging current. Self-discharge test module of function block diagram are shown in figure 1 below. The reference voltage as input of self-discharge detection circuit, by D/A conversion module according to the given digital MSP430F149 conversion analog voltage. Reference voltage can be manually set by buttons, measuring the self-discharge of battery under different voltage. First, by comparing the voltage link, the reference voltage comparing with the actual real time voltage of the battery, battery voltage and the reference voltage difference. When the battery voltage is higher than the reference voltage, charging circuit to stop working, the battery discharge automatically by the load resistance. When the voltage is lower than the reference voltage, charging circuit start working and charging, until the battery voltage stability. The charging current for charging voltage and current of battery discharge through the load resistance and self discharge current combined. The charging current measurement and calculation of discharge current value, the difference between the two is the self-discharge of the battery current value. In addition, although the reference voltage module sends the voltage of dc is in principle, but still would inevitably mixed with clutter, which can cause the vibration of the detection circuit, so you need to set up a low-pass filter to filter out high frequency interference. Considering when f & gt; F0 the signal frequency is greater than the cut-off frequency passband, logarithmic amplitude-frequency characteristics of the first-order low-pass filter in slow - only 20 db / 10 times frequency drops, voltage amplification factor can't immediately dropped to zero. Transition band width, filtering performance is poor. Therefore, using second-order low-pass filter circuit.