Battery Management Systems - Get the most out of your battery!

Battery Management System

Batteries are used to power everything from smartphones and power tools to electric vehicles. Depending on the required energy and associated dis-/charge currents, the battery pack is an assembly of individual li-ion cells connected in series and in parallel. A battery cell delivers approximately 4 V. A complete 400 V battery pack, for instance, features about 100 cells. As the cell chemistry is very sensitive to the exact dis-/charge current, voltage profile and temperature profile, the battery requires special monitoring and control capabilities. This is the role of the battery management system (BMS). The BMS monitors and balances each cell. It senses temperature, pressure, current and voltage, measures charge capacity (by counting coulombs) and tracks many other diagnostic metrics. Based on these parameters, it calculates – among other things - the state of charge (SoC), the state of health (SoH) and the precise consumption to predict how much energy is left for the application.

In addition, the BMS controls the main switch to protect the battery against critical overloads. In the event of thermal runaway, the BMS can derate or shut the battery down.

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Charged for success

Discover how our semiconductor solutions for battery management systems can help you get the most out of your battery while achieving the highest quality and functional safety standards.

Cell Monitoring Controller

The controller performs cell-level monitoring according to pre-adjusted voltages and temperatures using parallel high-precision ADCs for each cell in order to guarantee synchronous measurements. It controls charge balancing across multiple cells and offers advanced housekeeping functionality for periodically scheduled cell measurements and state analysis as well as alarms required for functional safety. This includes protection against over-/undervoltage and thermal stress. The monitoring controller is designed for extreme low-power and can be supplied directly from the monitored cells.

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Our AURIXTM microcontrollers enable functionally safe operation of the battery under all conditions and stress scenarios. They optimize the battery’s operational safety margins in order to withdraw maximum energy for longer rides and better cell lifetime. These controllers are available over a wide operating range, covering basic functions such as BMS calibration. They also support high-end functions such as SoC and SoH checks. Other highlights include special protective responses in the event of a crash or mechanical strain and a main protection switch to disconnect the battery in the event of an emergency. Furthermore, as the battery is an important and expensive asset of the vehicle, AURIX™ also includes the HSM for security to prevent illegal manipulation in situations such as tuning or to prevent billing fraud.

AURIX™ microcontrollers:

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The protection switch is a key safety element, enabling the battery to be disconnected in a controlled manner in the event of an emergency (risk of over-charging, short circuit or thermal run-away). If the switching characteristic of the relay is fast enough, it could also be used in traction applications to enable pre-charging of the main inverter DC bus without additional components. Our TLE9104SH relay driver is a smart 4-channel low-side switch in smart power technology with an 16-bit SPI for control and diagnosis. All channels are protected against overcurrent/overtemperature and have active clamping circuitry.

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Isolation monitoring is a key functional safety feature for high-voltage batteries. Alongside short circuit and overload current measurements, the voltage of the high-voltage DC+/- lines is continuously measured against the pack’s mechanical housing and the surrounding chassis. High-performance current sensors enable the current measurements captured to be also used for other battery monitoring and advanced battery diagnostics functions such as state-of-charge and depth-of-discharge calculations.

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(commercial/industrial qualified version only)

Advanced analytics are also performed at pack level with respect to thermal, electrical and mechanical strain. Highly accurate pressure sensing can detect extensions to the cell housing as a result of overload/overcharge conditions as well as mechanical impacts on the pack‘s mechanical structure. Sensing of evaporated CO2 from the cell’s electrolyte as a result of cell aging or overstress could be a vital indicator of battery health. Finally a combination of pressure and position sensors allows unauthorized pack manipulations to be detected.

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BMS electronic components such as controllers, sensors and gate drivers rely on integrated smart power supplies to operate the digital/analog/power ICs. Our auxiliary power supply components are available with full ISO26262 compliance for ASIL applications. They provide multiple voltage levels to supply the full system. In addition, they supply a dedicated reference voltage for highly accurate and load-independent ADC supplies. Our OPTIREG™ automotive power supply ICs, the TLF35584 for functional safe supplies or OPTIREG™ switcher with 1 – 6 channel buck-boost DCDC supplies give designers maximum flexibility.

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OPTIREG™ automotive power supply ICs for linear, switcher and PMIC devices:

Standard network protocols like CAN (Controller Area Network) and FlexRay are used for data exchange between the battery and external applications. Especially in vehicle battery applications, safety-related self-testing and monitoring functions increase the amount of time-critical data exchanged between the BMS and the ECUs. The automotive industry established the CAN FD (Flexible Data rate) protocol to accelerate CAN communications up to 5 Mbit/s, and the CAN PN (Partial Networking) method to improve energy efficiency. Our broad portfolio of automotive transceivers supports these protocols and methods while meeting and even exceeding the latest ESD and EMC requirements.

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Active thermal control is essential with high-voltage li-Ion batteries to avoid accelerated aging, reduced capacity even damage to the battery.

We offer various embedded motor controllers with in-built diagnostic functions supporting active thermal control solutions at pack level. These motor controls come in the smallest form factors with a minimum number of external components so they can be integrated close to the motor. They are based on our 32-bit microcontroller with embedded non-volatile memory, analog/digital peripherals, communication interfaces and integrated current-controlled bridge drivers.

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Cryptographic measures such as secured storage of certificates and keys help ensure that the battery management system “is only doing what it is supposed to do”. Cryptographic technologies can securely encrypt over-the-wire/-air software updates, store BMS-related sensitive data such as usage profiles, identify genuine or authenticated parts and components, and verify that a battery configuration remains within its intended design and operational limits. In addition, they can contribute to business success by protecting the IP of core BMS operation software.

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For more technical information, please visit our battery management system application page.