![]() The BQ79606A-Q1 precision battery monitor can measure up to six thermostats in a six-channel pack with high accuracy, providing plenty of redundancy to prevent failures in temperature monitoring. Today’s battery monitors have several general-purpose inputs/outputs (GPIOs) for temperature sensing. Monitoring and controlling the battery pack temperature is essential to maintain the health and safety of the pack and to prevent thermal runaway. In addition to external factors, some of the switching elements consume power and release some of that power as heat, contributing to a thermal increase in the battery case. A typical tolerable temperature for a battery pack is between 0☌ and 60☌. Lithium-ion (Li-ion) batteries do not tolerate extreme temperatures. This comparator function is entirely separate from the ADC function so, even if the ADC function fails, the analog comparators will still flag the crossing of under- and over-voltage comparator thresholds. The device has a set of window comparators that provides cell voltage monitoring for all six channels separately from the main acquisition path and works in parallel with the main ADC route. Take the example of BQ79606A-Q1 automotive precision battery monitor, balancer, and integrated protector from Texas Instruments it has six dedicated delta-sigma ADCs for each channel and an auxiliary ADC for redundancy. In case of failure or a drift in the measurement, during the safety diagnostics, the same cell measurement will be double-checked and measured against the same reading using an auxiliary ADC that has a completely independent path and reference. The redundancy is designed to detect any failure in one of the ADCs and serves to double-check the accuracy of the measurement from an independent ADC. Implementing two completely independent analog-to-digital converters (ADCs) with two independent paths can help achieve Automotive Safety Integrity Level D (ASIL-D) compliance according to the ISO 26262 standard. Additionally, measurement redundancy is critical to increase safety and prevent failure or drift over time. Battery monitors are designed to address all of these issues and help make EVs and HEVs safer.Īn inaccurately reported voltage can cause the MCU to overcharge the battery, potentially damaging the cell or causing thermal runaway. ![]() To prevent these events from occurring, monitoring the battery cells is crucial. ![]() High charging and discharging currents.Overcharging the battery beyond its maximum allowable voltage.An external short circuit that can cause the release of an unlimited amount of power, which heats up the cells rapidly.An internal short circuit in the battery cells if they become physically damaged after an accident or if an object penetrates the battery pack.Thermal runaway can be caused by several factors: This causes the battery to become gaseous, and a fire may erupt. When the temperature rises rapidly to 400☌, the energy stored in the battery is suddenly released. Thermal runaway is the primary cause of system safety issues within HEVs/EVs because it causes an unstoppable chain reaction. A bridge device is required in order to facilitate the communication between the host MCU and the stack devices.įigure 2 Battery monitors are stacked in a daisy-chain configuration. Every monitor in the stack transfers information through a communication line from the top of the stack to the bottom device. Each device connects to battery cells through sense lines to monitor every cell in the pack. In typical applications, the battery monitors are stacked in a daisy chain, as shown in Figure 2. a host microcontroller (MCU) that acts as the “brain” and coordinates all actions within the EV.įigure 1 illustrates a high-level architecture of an EV battery management system (BMS).įigure 1 A battery management system facilitates monitoring and control of the high-voltage battery stack in EVs/HEVs.battery monitors and current sensors that monitor the voltage, current, and temperature of the battery pack and.a power inverter that delivers energy from the battery to the electric motor.a DC/DC converter that bucks (steps down) the power to lower voltages in order to power car electronics such as the heater and automatic windows. ![]()
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