Table of Contents
- What Is an Automotive BMS (Battery Management System)?
- Configuration of Battery Monitoring Functions in Automotive BMS
- Benefits of Secondary Monitoring
- Why Is ABLIC's Automotive Protection IC Ideal for Secondary Monitoring?
- Application Circuit Example
- Product Lineup
- Packages
- Try Out ABLIC's Automotive Battery Protection ICs and EDLC Voltage Monitoring ICs
1. What Is an Automotive BMS (Battery Management System)?
An automotive battery management system (BMS) is a system mainly used in electric vehicles (EVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and e-Bikes to monitor and protect the battery, ensuring that it can be used safely and efficiently.
As the electrification trend accelerates in the automotive industry, the role of BMS, which is directly linked to vehicle safety, is becoming increasingly important. In particular, the function that detects dangerous battery conditions such as overcharging and overdischarging requires a high level of safety. Therefore, it is becoming more common for automotive BMS to be required to comply with functional safety (FuSa) standards such as ISO 26262.
Furthermore, as autonomous driving technology advances, the demand for enhanced safety mechanisms continues to grow. Today, the importance of fail-stop and fail-operational (continued functionality) mechanisms/applications is notably increasing.
2. Configuration of Battery Monitoring Functions in Automotive BMS
The battery monitoring in an automotive BMS typically consists of two systems: the primary monitoring system and the secondary monitoring system.
Primary monitoring: Composed of AFE (Analog Front End) IC and MCU
The primary monitoring system generally consists of an IC called an Analog Front End (AFE), which directly monitors the battery, and a MCU that controls these components. Since automotive batteries are configured with numerous cells connected in series to achieve high voltage, the AFEs are also connected in a cascade configuration.
In addition to the AFE and MCU, the primary monitoring system includes a bridge IC that serves as a communication interface between the AFE and MCU, a watchdog timer (WDT) that monitors the operation of the MCU, a power IC that supplies power to the MCU, and a voltage detector (VD) that monitors the output voltage of the power supply IC.
Secondary Monitoring: Composed of Automotive Battery Protection IC
The secondary monitoring system also monitors the battery, similar to the primary monitoring system. By incorporating a secondary monitoring system, the automotive BMS more secure and robust.
The following benefits can be obtained by incorporating a secondary monitoring system:
- Battery monitoring can continue even if the primary monitoring system fails.
- It enhances the BMS's functional safety level (ASIL decomposition), with minimal effort.
3. Benefits of Secondary Monitoring
This part highlights the benefits of incorporating a secondary monitoring system into an automotive BMS.
Monitoring Continuity
The initial benefit is monitoring continuity, which allows the secondary monitoring system to continue monitoring the battery even if the primary monitoring system fails.
The functional safety standard ISO 26262 requires that faults within the automotive battery/BMS with significant impact be promptly detected and safety ensured. If a fault is detected by the primary monitoring system, the driver is notified through the system. However, if the battery monitoring system is unable to monitor the battery cell voltage, it may not be possible to continue driving for safety reasons.
With a secondary monitoring system in place, battery monitoring can continue even if the primary monitoring system fails. Achieving such monitoring continuity aligns with the concept of fail-operational (continued functionality). Especially with the expected expansion of autonomous driving systems, where automated systems may increasingly become more responsible for making decisions and taking actions on behalf of the driver during trouble, this kind of monitoring continuity is becoming increasingly important.
ASIL Decomposition
The next benefit is that it's easier to enhance the functional safety level of the BMS when incorporating a secondary monitoring system, compared to only relying on the primary monitoring system alone.
For example, if the required functional safety level of the BMS is ASIL-D, each component of the monitoring system, such as the AFE, MCU, and bridge IC, must also be ASIL-D compliant. Additionally, the software loaded onto the MCU must meet the same functional safety level. Achieving ASIL-D compliance increases the complexity of these components, leading to higher development effort and increased costs.
In contrast, adding a secondary monitoring system allows for the decomposition of ASIL-D requirements, making it easier to achieve ASIL-D for the BMS. If the existing monitoring system meets ASIL-C requirements, achieving ASIL-D at the BMS level becomes feasible by incorporating a secondary monitoring system that can use ASIL decomposition.
However, for decomposition to be valid, the primary and secondary monitoring systems must be independent of each other and not share common cause failures (i.e., failure modes where both systems would lose functionality). Therefore, several conditions need to be met for decomposition to be effective.
4. Why Is ABLIC's Automotive Protection IC Ideal for Secondary Monitoring?
ABLIC's automotive battery protection IC is the ideal choice for secondary monitoring systems.
Battery Monitoring Independent from MCU
ABLIC's automotive battery protection IC operates in a standalone mode, eliminating the need for MCU control. This simplifies the secondary monitoring circuit and eliminates the need for software development.
Constant Operation with Low Current Consumption
ABLIC's automotive battery protection IC provides monitoring functions focused on detecting more critical failures, such as overcharging and overdischarging. As a result, it can maintain low current consumption even when continuously monitoring the battery, thereby minimizing the increase in the BMS's standby current.
Certified Development Process
ABLIC has obtained development process certification for ISO 26262 from SGS-TÜV Saar GmbH (Germany), a third-party certification body. Based on this standard, ABLIC's automotive battery protection IC, developed in accordance with SEooC, is highly suitable for automotive BMSs that require advanced safety.
Ease of Decomposition
As mentioned earlier, for the decomposition of the primary and secondary monitoring systems to be applicable, it is necessary that the primary and secondary systems are independent of each other and there are no common cause failures.
ABLIC's automotive battery protection IC is a completely different type of IC compared to combinations of AFE and MCU, as it independently monitors directly from the battery, eliminating concerns about common cause failures.
The S-19192 Series and S-19193 Series achieve ASIL-B on their own, allowing them to be combined with an ASIL-C primary monitoring system to form an ASIL-D automotive BMS.
5. Application Circuit Example
Protection Circuit Example using automotive secondary protection IC S-19193 Series
6. Product Lineup of Automotive Battery Protection ICs / EDLC Voltage Monitoring ICs
| Product name | Data- sheet | Safety manual | FuSa category | Number of cells | Overcharge | Over- discharge | Cascade connection | Cell balancing | Power- saving | Self- test | Buy online | ||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1 | 2 | 3 | 4 | 5 | 6 | 7 or more | |||||||||||
| S-19193 | FuSa process compliant | – | – | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ | – | – | ✓ |     | ||
| S-19192 | – | FuSa process compliant | – | – | ✓ | ✓ | ✓ | ✓ | – | ✓ | ✓ | – | – | – | ✓ | | |
| S-19190 | – | FuSa supportive | ✓ | – | – | – | – | – | – | ✓ | – | – | ✓ | ✓ | – | | |
7. Packages
