Reduce automotive electrical failure by using precision lithium battery detection and sensing technology

　　Author ：Iflowpower – Portable Power Station Supplier

Every five cars failure is one of the batteries. In the next few years, with the increasing popularity of automotive technologies such as electrical transmission, start / flameout engine management and hybrid (electricity / gas), this issue will become more and more serious. In order to reduce the fault, the voltage, current, and temperature of the battery are accurately detected, and the results are pretreated, the charging state and the operating state are used, and the results are sent to the engine control unit (ECU), and the control charging function.

Modern cars were born in the early 20th century. The first car rely on manual startup, with great strength, there is a high risk, and this hand crank of the car has caused a lot of death. In 1902, the first battery started motor was successfully developed.

By 1920, all the cars have been started. The initial use is a dry battery. When electric energy is exhausted, it must be replaced.

Soon, the liquid battery (ie the ancient lead-acid battery) replaces the dry battery. The advantage of the lead-acid battery is when the engine is working, it can charge from. In the last century, there is little change in lead-acid batteries, and the last important improvement is to seal it.

True change is the needs of it. At first, the battery is only used to start the car, the horn and power supply for the lamp. Today, all electrical systems of the car must be powered before ignition.

A surge in new electronic devices are not just GPS and DVD players and other consumer electronic devices. Today, the engine control unit (ECU), the electric car window and the electric seat, and the body electronic device such as the electric seat has become a standard configuration of many basic models. The new load of the exponential level has seriously affected, and the failure caused by the electrical system is increasingly the evidence.

According to the ADAc and RAC statistics, almost 36% can be attributed to electrical failure in all car failures. If the number is analyzed, it can be found that more than 50% of the fault is caused by the components of the lead-acid battery. Two key features below the battery should reflect the health of lead-acid batteries: (1) Charging state (SoC): SOC indicates how much charge can be supplied, the battery rated capacity (ie, the new battery SOC SOC) percentage representation.

(2) Operation status (SOH): SOH indicates how much charge can be stored. The charging state charge status indication is better than the battery's fuel gauge. There are many ways to calculate the SOC, two of which are two: open circuit voltage measurement method and Coulomb assay (also known as Coulomb counting method).

(1) Open circuit voltage (VOC) measurement method: Condensed relationship between open circuit voltage and its charging state during battery-free. This calculation method has two basic limits: First, in order to calculate the SOC, the battery must open, no load; the second is that this measurement is only accurate after a considerable stability period. These limitations make the VOC method not suitable for online calculation of SOC.

This method is usually used in a car repair shop, where the battery is removed, and the voltage between the positive and negative electrical poles can be measured with a voltage table. (2) Coulomb assay: This method uses Coulomb Count to take the current to time points, thereby determining SOC. Using this method, the SOC can be calculated in real time, even if the battery is under load conditions.

However, the error of the coulomb measurement will increase over time. It is generally comprehensively using open circuit voltage and coulomb counting to calculate the charging state of the battery. The operating status of the running state reflects the general state of the battery, and its ability to store charge compared to new batteries.

Due to the nature of the battery itself, SOH is very complicated, depending on the chemical composition and environment of battery. The battery's SOH is affected by many factors, including charging acceptance, internal impedance, voltage, self-discharge and temperature. These factors are generally considered to be difficult to measure these factors in real-time environments in the automotive environment.

In the startup phase (engine start), the battery is under the largest load, at this time, the SOC and SOH calculation methods actually used by the lead battery sensor developer actually used by the leading automotive battery sensor developers are highly confidential, often being patented. Protect. As the owner of intellectual property, they usually work closely with VARTA and MOLL to develop these algorithms.

Figure 1 shows the commonly used discrete circuit for battery detection. Figure 1: Separate battery detection solution This circuit can be divided into three parts: (1) battery detection: battery voltage detects by a resistive attenuator directly from the battery positive electrode. To detect current, a detection resistor (12V application is generally used in 100Mω) Among battery negatives and ground.

In this configuration, the metal chassis of the car is generally, and the detection resistance is mounted in the current circuit of the battery. In other configurations, the negative electrode of the battery is. About SOH calculations, you must also detect the temperature of the battery.

(2) Microcontroller: Microcontroller or MCU important completion two tasks. The first task is to process the result of analog converter (ADC). This work may be simple, such as only basic filtering; it may be complex, such as calculating SOC and SOH.

The actual function depends on MCU's processing capabilities and car manufacturers' needs. The second task is to send the process through the communication interface to the ECU. (3) Communication interface: Currently, the local interconnect network (LIN) interface is the most common communication interface between battery sensors and ECUs.

Lin is a single line, low cost alternative to a wide-known CAN protocol. This is the easiest configuration of battery detection. However, most precision battery detection algorithms require both battery voltages and current, or battery voltage, current and temperature simultaneously.

In order to make synchronous sampling, you have to add up to two analog to digital converters. In addition, the ADC and MCUs adjust the power supply to work correctly, causing new circuit complexity. This has been resolved by the Lin transceiver manufacturer by integrating the power supply.

The next development of automotive precision battery detection is integrated ADC, MCU and Lin transceivers, such as ADU's AduC703X Series Precision Simulation Microcontroller. AduC703X supplies two or three 8KSPs, 16-bitσ-Adc, a 20.48MHzarm7TDMIMCU, and an integrated Linv2.

0 compatible transceiver. The ADUC703X series is integrated with a low pressure difference adjuster, which can be powered directly from the lead-acid battery. In order to meet the needs of automotive battery detection, the front end includes the following device: a voltage attenuator for monitoring the battery voltage; a programmable gain amplifier, with 100mωWhen using the resistor together, support the full-scale current of 1A to 1500A; a accumulator, support coulomb count without software monitoring; and a single temperature sensor.

Figure 2 shows a solution to this integrated device. Figure 2: Solution to integrated devices An example of a few years ago, only high-end cars is equipped with a battery sensor. Today, there are more and more medium and low-end cars for installing small electronic devices, and it can only be seen in high-end models ten years ago.

The number of faults caused by lead-acid batteries is therefore continuously added. After a few years, each car will install the battery sensor to reduce the risk of increasing the risk of the electronic device.