With daily life in portable applications have emerged more and more, the
rechargeable batteries become more important than ever. They are widespread in the laptop pc, cellular phone, pda and more applications in the future. Pc laptop in the more powerful, more compact size, low price, while its battery standby time is not the same speed increase. Bluetooth is a 24-hour active color display and a new type of cellular phone, also shorten the waiting time. Chemical battery technology reached a moderate stage of development, unprecedented growth has not kept pace with the demand for portable applications, such a situation to the battery manufacturers have brought tremendous pressure. Waiting for a breakthrough in fuel cell technology, while vendors for rechargeable batteries to the complexity of chemical products, through
improved battery management design, greater access to energy. Lithium-ion battery technology Today’s portable applications widely used in
rechargeable battery technology is the chemical lithium-ion technology, energy density is about 100 wh / kg, is portable applications. Performance of its products is the nearest nimh, the energy density of 75 wh / kg. Pc in the laptop, with other electronic components become smaller, lighter, battery has become the total weight on an increasingly prominent part. Cost is not particularly high in the circumstances, light energy will be favored. Lithium-ion technology they have very low self-discharge rate, low maintenance and relatively short charging time, able to compete successfully in today. As lithium-ion in the management and monitoring is also a highly complex chemical technology, therefore, the paper will be pc laptop batteries as an example, focus on the technology. The lithium-ion technology issues Lithium-ion technology is not perfect embodiment, although low self-discharge rate advantage is its life, but it still faces some impact on the life of other factors, see Figure 1. The first is the problem of aging batteries. Lithium-ion batteries from the manufacturer at the start even if not, will gradually lose its full charge capacity (fcc). This aging rate depends on
temperature and battery charging status. Pc laptop batteries most often deposited in the office environment, that is, 100% charge and at room temperature conditions. Under such conditions, the battery will lose its annual fcc of 20%. The temperature is higher than 25 ?, stolen, will be more serious. This problem can reduce the storage temperature and charge state to be resolved. In 40 percent of capacity and 0 ?, the annual loss of battery power is about 4 per cent of its fcc, but it will challenge the flexibility of working at portable applications. Clearly, the actual lithium-ion battery life than the expected short. Decided to lithium-ion batteries in the health status of the life cycle is another factor
that the battery in its power greatly reduced tolerance before the charge / discharge cycle a few. Lithium-ion batteries with low maintenance, is that they do not require users to battery “deep cycle (deep cycle)”, as nicd nimh batteries or in the case. In fact, a deep discharge cycles will actually increase the impedance of the battery, reducing its capacity. Lithium-ion battery voltage level below a certain value (for the traditional 2 v) will be permanently damaged. The latest technological developments to further reduce the minimum voltage value, but it still exists. When the battery impedance increases, the battery voltage current load will soon dropped this low, reducing the need for rechargeable batteries before the effective running time. In addition, the cycle of life will be shortened as the temperature increases. Early intelligent power management system Pc laptop users certainly do not want to pc battery storage to the refrigerator, in power do not want to run out before, always worrying about battery use the remaining time. To this end, the laptop power supply designers to design power management system to calculate
battery life, and a reliable feedback to use the remaining time. This feature laptop pc commitment from the past, but are now usually from their own internal battery completed. In order to fcc and the battery life cycle to make a good estimate, power management systems need to understand the aging batteries and the number has been recycled. pc battery life than the head, not only with a battery, will be above those parameters stored in a battery cell itself, stored in the pc than in the more appropriate. Some other help to enhance the accuracy of estimates of the parameters are temperature logging and cyclical battery impedance measurement. The use of modern smart battery technology is to increase the
battery capacity of a viable programme. Early today, and some battery management systems, and batteries do not fcc specific real-time assessment of the necessary parameters to track. This system is a surplus of electricity is estimated that the battery does not consider the degradation of state. This surplus capacity is expected to increase over time become increasingly inaccurate, the results will have two situations. If a case is the valuation of the remaining capacity for optimism, then the battery failure, and the pc still on the screen indicates that the battery is also available in time. This usually caused by the user’s dissatisfaction, which are often avoided by the designers. Another case is the valuation of surplus electricity for the pessimistic, although this method will not appear ahead of the end of
battery life, but to a certain extent, the residual waste of electricity. Many designers still prefer the battery pessimistic estimation. Coulomb counting method Keep the battery pack fcc forecast for the remainder of the real-time electricity consumption is estimated to provide a more accurate basis. This will
enable battery designers can reduce the estimated surplus of electricity, “protected areas”, thereby increasing user access to electricity from the battery pack the actual time. Fcc to maintain real-time estimates of modern smart battery technology is not the challenges faced by the end. Users concerned about the stability of the remaining power, this figure depends on the state of rechargeable batteries, rechargeable battery status equivalent to the fcc cut so far consumed power. In addition, the remainder of a battery depends on the load current valuation. Users through a wireless lan way to full brightness in their lcd screen tv programmes broadcast on the flow of electricity consumption, only documents than in the operation and no other peripheral devices running the circumstances much more. In the development of the battery monitoring system from the battery voltage is estimated charge state. This approach also applied for the pc battery not sufficiently precise. Batteries need time to track the inflow or outflow of current, and record their total. This monitoring method known as Coulomb count (coulomb counting), see Figure 2, it needs to accumulate points or adc fixed to monitor the inflow or outflow of current battery. Through Coulomb count,
batteries can also know that the remaining number of its own electricity. Know the remaining capacity, the remaining time will be able to load from the current continuous measurement of the estimated. In short, the smart battery of modern technology must be able to tell users in the current load, how long the battery can use. To enable the accurate valuation of as much as possible, the battery needs: ? adc monitor the use of high-resolution current load; ? Coulomb Counter calculated using the surplus electricity; ? use cycle counter (usually stored in eeprom in a value), battery life, temperature logging, based on simultaneous real-time measurement of voltage and current parameters
such as battery impedance calculation of the battery charge of the whole. Available to the user’s end-use batteries fcc time will be left to the charge state calculated, it depends on the load on the battery, taking into account impedance of the battery, so as to avoid damage of a low voltage. Coulomb counting methods used to achieve the remaining capacity calculation is a great challenge. It requires a dedicated high-pressure-resistant analog circuits for monitoring, non-volatile memory for parameter storage and a powerful cpu to calculation. atmel atmega 406 companies to provide the smart battery mcu can be achieved Coulomb count programme. atmega 406 with an on-chip voltage regulator can directly from the pc battery to 4 ~ 25 v the scope of supply. It has four high-voltage differential resistance adc access to the
lithium-ion battery up to four separate monitor. atmega 406 inside a cumulative two-way automatic Coulomb Counter, a 18 per second have tired of value-added. The voltage and temperature measurements, a 13 the sigma / delta adc. atmega 406 based on the commonly used avr (r) 8 architecture, a 40 kb on-chip memory and 512 b procedures of the eeprom (used to store parameters). Sm-bus device equipped with communications functions, the lqfp a 48-lead package. It is also an independent ad hoc battery protection circuit. Summary
Intelligent battery within the ingenious use of microelectronics technology for battery users a lot of convenience. Intelligent power management system to achieve a simple understanding of the programme is not battery charging status, and battery life before the arrival of the shutdown, or show than the actual available capacity of slightly less electricity. Another programme that is a mature Coulomb count, can the life of the battery, the use of history, load status and charging parameters such as track, to provide users with the best safety of the remaining time estimated
