Remote meter equipment due to its special working conditions and work requirements of the battery is very high. It requires the battery has a longer continuous power supply capacity, battery life time is often needed to reach a year or even longer.Because of the lithium batteries high voltage, small size, light weight, high energy density, no memory effect, no pollution, low self-discharge, long cycle life, the many advantages of being widely used in remote monitoring long standby instrument. Compared with nickel-metal hydride batteries, lithium-ion battery 30%-40% lighter, energy 60% higher than it. However, lithium also has serious flaws, is summarized in the following two aspects:
Lithium battery security is poor, when an explosion and other defects. Especially lithium cobalt oxide cathode materials for lithium batteries can not be high-current discharge, poor security. In addition, almost all kinds of lithium battery overcharge or over-discharge can cause irreversible damage. Lithium battery temperature is extremely sensitive: if used in high temperature conditions, may cause decomposition of the electrolyte, combustion or explosion; temperature is too low will lead to a marked deterioration in the performance of lithium batteries, affect the normal use of the equipment. Due to limitations in the battery production process, the internal resistance of each cell, there will be differences in the capacity etc. When a plurality of battery cells in series, will cause the rate of charging and discharging batteries various inconsistencies, which led to the utilization of the battery capacity is low. In view of this, the lithium battery in the actual use of the process often requires special protection system to monitor the health status of the battery, lithium batteries use to manage the process. Shows the decomposition of the electrolyte of the lithium battery.
Lithium battery capacity at low attenuation and power makes the device unable to accurately predict poor maintainability. A long line of instruments require periodic battery replacement, and remote monitoring equipment to work sites scattered on the road between the various remote sites, so the battery replacement huge workload and costly. In order to reduce the maintenance workload, reduce maintenance costs, it requires a battery management system with an accurate estimate of the state of charge function to accurately grasp the battery state of charge, battery replacement and more destinations; also need a battery management system with a lower its power consumption to reduce the frequency of maintenance and prolong battery life. Therefore, long-lasting power for remote monitoring instrument, the rational design of battery management system to maintain the device has a very important significance.
However, the working characteristics of remote monitoring instruments and inherent characteristics of lithium batteries make such an application developed to meet the requirements of the battery management system becomes very difficult. There are several factors: First, from the working characteristics of distance measuring instruments concerned, in order to reduce power consumption, remote measurement instruments typically carried out periodically sleep and wake, and its current work is dynamic, wake-up phase of the current much higher than hibernation, but the wake-up phase of the working time is far less than the dormant stage; secondly, lithium battery discharge curve is very flat, the main power concentrated in 3.6V voltage or more, and then, with further reduction in voltage, battery charge began a sharp decline, remote instrumentation can not be issued in accordance with the battery voltage is low battery alert; Finally, the lithium battery self-discharge rate changes with temperature fluctuated for work in the field of instrumentation, the temperature conditions are very extreme, and further increase the battery is difficult to predict. Existing battery management system is difficult to adapt to these functional and performance requirements, based on the background of the subject is proposed.
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