Nickel-Metal Hydride Batteries Ideal for Backup Power in Automotive TCUs

Background

The automotive industry is undergoing a major transformation driven by the adoption of advanced technologies such as electrification and autonomous driving. As a result, the value of vehicles is shifting significantly. Traditionally, vehicle value was primarily derived from hardware elements such as engine performance, fuel efficiency, and body design. Today, however, the value of software features—such as systems that support safe and smooth driving and in-vehicle entertainment—is rapidly increasing.

Such software can be continuously updated to enhance vehicle functionality and user experience, making it a key factor in maintaining and increasing vehicle value over time. The Telematics Control Unit (TCU), an onboard communication device, plays a central role in enabling these software updates and external connectivity. TCUs facilitate communication between the vehicle, the cloud, and other devices, serving as a core component for the next-generation mobility services.

Configuration and Operation Image of the TCU

One of the functions of the TCU is the eCall system, which automatically sends emergency alerts containing vehicle status and location information if an accident occurs. This enables prompt emergency response and improves occupant survival rates. Since 2018, Europe has mandated eCall systems in new vehicles.

Challenges of TCU Backup Power

To ensure dependable operation of the eCall system under all conditions, a reliable power supply is essential. Power to the TCU is normally supplied by the vehicle’s 12Volt Lead-Acid battery. A backup battery, however, is designed into the TCU to ensure uninterrupted power if main power is lost due to events such as an accident.

Requirements for Backup Power

The TCU backup battery must meet several requirements. First, it needs to have enough capacity to transmit the vehicle’s location to the

emergency call center and to support voice communication between the occupants and emergency responders for a specific amount of time.

The capacity requirement must be balanced with the size limitations to ensure it fits within the space of the in-vehicle equipment.

Depending on where the vehicle is driven and the TCU is installed, the battery may be exposed to a wide range of temperatures—from extreme heat to cold. Therefore, it must deliver stable performance across a broad temperature range. The ensures reliable operation of all critical functions such as the eCall system even in harsh environments.

Impact of Advancing In-Vehicle Cellular Communication

Currently, in-vehicle cellular communication primarily uses 3G/4G, but the adoption of 5G is expected to accelerate. The use of 5G, including millimeter-wave bands, will enable high speed and high capacity data transmissions, but will also increase the TCU power consumption.

Image of TCU Installation on the Roof Area

Communication between the vehicle antenna and the TCU is conducted via cables. Longer cables can lead to transmission and power losses. As a result, placing the TCU near the antenna—such as on the vehicle roof—is being considered instead of the traditional dashboard location. However, the roof is exposed to direct sunlight and high temperatures, requiring the TCU and its internal backup battery to have high heat tolerance.

Panasonic Energy’s TCU Backup Battery

Nickel-Metal Hydride (NiMH) batteries with their wide operating temperature characteristics are ideal for TCU backup power. Our newest model, BK120AAWX, pushes the temperature limits to an industry best, 105°C.

Examples of Our Products for TCU Applications

Wide Operating Temperature Range

This figure shows the results of a storage test under extremely high temperatures (105°C). Even after 150 hours, the battery will recover most of its capacity. This ensures reliable backup power performance even when the TCU is installed in high-temperature areas such as the roof or dashboard.

Capacity Degradation Characteristics During High-Temperature Storage

Image of TCU Installation on the Roof Area

This figure presents discharge test results in low-temperature environments. The battery maintains over 80% discharge efficiency compared to room temperature, even at -30°C and -20°C. This makes it effective not only in hot climates but also in cold regions.

Discharge Characteristics in Low-Temperature Environments

Long-Term Durability

Backup batteries in TCUs are intermittently charged to maintain a full charge. Durability can be evaluated through intermittent charging tests※. Figure shows the results of such a test under accelerated temperature conditions. Even after repeated charge-discharge cycles at 45°C, the battery maintains stable capacity, providing a reliable backup power source in emergencies.

Battery life will vary depending on the battery type, environment and usage conditions. Panasonic Energy can leverage its extensive knowledge and experience to recommend a battery that will maximize the performance based on the customer’s requirements.

Energy can leverage its extensive knowledge and experience to recommend a battery that will maximize the performance based on the customer’s requirements.

※intermittent charging

Intermittent charging refers to the repeated process of restoring a battery to full charge after a certain amount of capacity loss due to self-discharge from a fully charged state.

Capacity Degradation Characteristics Under

Battery Pack Configuration

Panasonic can supply a unique energy solution based on our customers’ needs. This includes multi-cell packs in various configurations with lead wires and requested connectors.

Examples of Nickel-Metal Hydride

Stable Global Supply Chain

Panasonic Energy’s resources include multiple factories and sales offices strategically located in various regions around the world. This local

footprint and communication enable Panasonic to supply and service our customers’ needs quickly and efficiently.

Panasonic Energy supports a higher standard of living through advanced battery technology in the healthcare, infrastructure and automotive markets. We are committed to a sustainable society where enriched living and the environment coexist.