Electric vehicle lithium battery capacity meter solution design

　　Author ：Iflowpower – Portable Power Station Supplier

Tags: Battery Capacity Power 1 Preface Environmental Protection (Abbreviation) is due to environmental pollution problems due to production development too serious, first caught attention to the attention of developed countries, and gradually cause the whole society to pay attention to the importance of national laws and regulations and public opinion propaganda. Measures to defend the ecological environment and effectively handling pollution problems by developed countries to develop my country. In fact, not only electric vehicles should battery capacity, many use batteries have an urgent requirement.

The traditional means of battery monitor is only a voltmeter, but the voltage does not accurately reflect the capacity of the battery, often has normal voltage, but there is no capacity. As a user often feels confusion, I don't know how long the battery can be used, so I affected the use of many key occasions, it is easy to cause accidents. Therefore, it is necessary to develop a instrument reflecting battery capacity.

At present, there are similar products in foreign countries, but may not see the method of implementation due to technical confidentiality. In this paper, the electric vehicle is used to use the object, and a battery capacity implemented by an electric metering method can be measured under certain conditions. It is based on such a principle that the battery is calculated and multiplied by the corresponding loss coefficient to indicate the capacity of the battery (the coefficient should take into account the battery capacity of the battery and the battery discharge current.

influence). 2 Basic principle The performance parameters of the battery are important for electromotive, capacity, specific energy and resistance. Electric potential is equal to the unit positive charge from the negative electrode to the positive electrode inside the battery, the power made by the battery is not static (chemical).

The electric potential depends on the chemical properties of the electrode material, independent of the size of the battery. The total charge amount of the battery can be the capacity of the battery, which is usually used in ampere hours. In the battery reaction, the electrical energy of 1 kg reaction substance is called the theoretical ratio energy of the battery.

The actual capacity of the battery is smaller than energy than the theory. Because the reactants in the battery are not fully charged, the battery internal resistance also causes an electric potential, so it often called high energy batteries than energy. The larger the area of ​​the battery, and the internal resistance is small.

In addition to some battery itself, it is obvious that the capacity can be measured if the amount of charge and discharge of the battery can be recorded. We envisage this instrument referred to as a battery capacity on a single battery to achieve the purpose of display capacity. This capacity is moving the summary of the battery to charge the sum of electricity and discharged the total power and the calculation is intuitive.

Other factors affecting battery capacity are synthesized as a loss coefficient, which multiplies the calculation amount of charge and discharge and the remaining capacity of the battery. Due to the type, size and performance of the battery, the loss coefficient is different, the important relying on the test, so it does not discuss the coefficient problem, only the circuit that completes the function of the metering power. Battery capacity refers to the size of the battery storage capacity.

The unit of the battery capacity is MAH, the Chinese name is mAh (when measuring a large-capacity battery such as a battery, for convenience, the Chinese name is presented, the Chinese name is safe, 1AH = 1000mAh). If the rated capacity of the battery is 1300mAh, if the battery is discharged in a current of 130 mA at 0.1 C (C is battery capacity), then the battery can operate for 10 hours (1300 mAh / 130 mA = 10h); if the discharge current is 1300mA, that is powered Time is only about 1 hour (there are some differences in actual working hours due to the actual capacity of the battery).

This is an ideal condition, and the current when the digital device actually works, it is not always constant in a certain value (as a digital camera as an example, the working current will be larger due to the LCD display, flash, etc. Change), so the battery can only be a approximate value to a power supply time of a device, and this value is only estimated by actual operation related experience. Battery charge and discharge has a variety of ways, constant current, limiting, pulse, negative pulses, etc.

, so simply uses current multiplied by time metering capacity, which cannot be adapted to other modes except for constant flow, and integral mode does not adapt to negative The pulse is charged, and it is not suitable for time parameters. No matter what charging, it affects the key parameters of the battery capacity, which is current and time, and the negative pulse charge is only negative. To this end, we have designed the battery capacity circuit of the following working mode, the principle block diagram shows Figure 1.

Figure 1 Battery capacity gauge matrix first monitors the charge and discharge current of the battery, and convert it to the voltage signal to amplify, and send the voltage frequency converter to change the frequency signal, display the count value by a certain manner, which constitutes One battery capacity. In fact, the frequency of the frequency represents the magnitude of the current, the current is high, and the number of pulses recorded in the same time, and vice versa. The charge and discharge time is also reflected in the counting of the pulse, counting more than the number of times.

In this way, the calculation of battery charging capacity is completed using the counting method. In a chemical battery, chemical energy is directly transformed into electrical energy, and the results of spontaneous oxidation and reduction in the battery are spontaneously carried out. This reaction is carried out on two electrodes.

The negative electrode active material consists of a reductant having a stable reducing agent in an electrolyte, such as zinc, cadmium, lead or the like, such as zinc, cadmium, lead or hydrogen compound, etc. The positive electrode active material is composed of a potential and a stable oxidant stabilized in an electrolyte, such as metal oxide, oxygen or air, halogen and a salt thereof, an oxygen-containing acid and a salt thereof, and the like. The electrolyte is a material having a good ion conductivity, such as an aqueous solution of acid, alkali, salt, an organic or inorganic non-aqueous solution, a molten salt or a solid electrolyte, etc.

When the outer circuit is disconnected, although there is a potential difference (open circuit voltage), there is no current, the chemical energy stored in the battery is not converted to electrical energy. When the external circuit is closed, there is a current flowing over outer circuit under the use of the two electrode potential difference. At the same time, in the inside of the battery, since there is no free electron with free electrons in the electrolyte, the transfer is inevitably accompanied by oxidation or reduction reaction of the e-polar active material and the electrolyte interface, and the material migration of the reactant and reaction product.

Free energy increment (focus) to Gibbs; F is the rule of Faraday = 96500 library = 26.8·Hours; N is the number of times the battery. This is the basic thermodynamic relationship between the battery electromotive force and the battery reaction, and it is also a basic thermal program of calculating battery energy conversion efficiency.

The combination of the two absolute amplifiers and the reversible counters realize the measurement of the discharge gap (ie, negative pulse charging), and completes the calculation of the two directions of charge and discharge by a set of circuits. When the charging is measured, the reverse count (decrease) when discharge is discharged, and the count direction of the reversible counter is controlled. 3 Method Declaration and Technical Key Solution 3.

1 Purpose of Current Sample Current Sample The purpose is to turn the current signal to a voltage signal, generally there are three ways: (1) sampling resistance; (2) splitter; (3) Hall device. From the use of electric car batteries, the current is large, obviously used the sampling resistance is not suitable, and the shunt is too heavy and the volume is also large, and the Hall device is applied. In addition, the size is small, and the weight is lightly installed on the car.

Its disadvantage is that the price is more expensive, but it is completely ignored about battery prices used in the car. Due to the choice of mature products that can be purchased, the circuit is simpler is not listed.