How to Specify a Thermal Battery for One-Shot Mission Power

Thermal batteries serve as highly reliable, maintenance-free, primary power sources for single-use applications, particularly in munitions, missiles, and other one-shot systems. Unlike conventional batteries, they remain inert and indefinitely stable until an internal heat source is activated, melting a solid electrolyte and enabling electrochemical reactions. This characteristic provides exceptional shelf life, instantaneous power delivery upon demand, and robustness across extreme environmental conditions. Specifying the correct thermal battery requires a systematic evaluation of mission-critical electrical, mechanical, and environmental parameters to ensure optimal performance and system reliability.

Key Specification Parameters

Designing a one-shot system around a thermal battery necessitates a precise definition of its power requirements. The following parameters are crucial for selection:

Activation Time

Activation time is the duration from the initiation of the thermal activation mechanism (typically an electrical signal to an igniter) to the battery reaching its specified output voltage. For applications demanding immediate power, such as ejection systems or early-phase guidance activation, a sub-second activation time is critical. For example, the Ultra-Fast Activation Thermal Battery (28 V, <100 ms) is designed for activation in under 100 ms. Other series, like the 50–56 V Thermal Battery Series, offer activation under 0.8 s, while the 90 V Thermal Battery Series and High-Power Thermal Battery Pack (>100 V, >5 kW) activate within 1.0 s. Conversely, the 28 V Thermal Battery Series offers a range from 0.5–2.5 s, accommodating various activation speed requirements.

Operating Life (Duration)

Operating life, or duration, is the period during which the battery maintains output voltage and current within specified limits after activation. This parameter directly correlates with the mission duration of the one-shot system. Short-duration applications, such as fuzing or safe-arm mechanisms, may only require seconds of power, while complex guidance systems or loitering munitions could demand minutes or even hours. The Long-Duration Thermal Battery (28 V, 5800 s) is an example, providing 28 V at 12 A for up to 5,800 seconds. The 28 V Thermal Battery Series covers a broad range from 60 s to 3600 s, and the High-Voltage Thermal Battery Series (100–150 V) supports durations up to 900 s.

Voltage and Capacity Sizing

Voltage: The nominal voltage, operating voltage range, and ripple characteristics must match the system’s power conditioning and electronic component requirements. Thermal batteries are available across common bus voltages. For instance, GNC Tech offers 28 V Thermal Battery Series, 50–56 V Thermal Battery Series, and 90 V Thermal Battery Series, as well as high-voltage options like the High-Voltage Thermal Battery Series (100–150 V) (100–150 V platforms) and the High-Power Thermal Battery Pack (>100 V, >5 kW) (over 100 V).

Capacity: This refers to the total electrical charge the battery can deliver, typically measured in Ampere-seconds (As) or Ampere-hours (Ah). Capacity is calculated by integrating the current draw over the entire operating life, including peak loads. For example, the 28 V Thermal Battery Series ranges from 50 As to 60,000 As, while the High-Voltage Thermal Battery Series (100–150 V) offers capacities from 880 As to 40,000 As.

Load Profile

Beyond nominal voltage and total capacity, the load profile – the variation of current draw over time – is critical. Many one-shot systems exhibit dynamic load profiles with significant current pulses for actuators, RF transmissions, or ignition sequences. The battery must be sized to handle both continuous average current and peak pulse current requirements without excessive voltage drop. Products like the High-Voltage Thermal Battery Series (100–150 V) support pulse currents up to 300 A, the 90 V Thermal Battery Series up to 180 A, and the 50–56 V Thermal Battery Series up to 120 A. High power output, such as the High-Power Thermal Battery Pack (>100 V, >5 kW) delivering over 5,000 W peak, or the 90 V Thermal Battery Series at up to 5,373 W, accommodates demanding power delivery needs.

Storage Life

One of the primary advantages of thermal batteries is their extended storage life in an unactivated state, often referred to as shelf life. This is paramount for munitions and emergency systems that must remain ready for deployment over many years without maintenance or periodic charging. Typical requirements range from 10 to 20 years, with some designs, like the Ultra-Fast Activation Thermal Battery (28 V, <100 ms), offering storage life over 15 years.

Environmental Requirements

Thermal batteries operate across a wide range of environmental conditions. Key considerations include:

Temperature: Operating temperature range (e.g., -54°C to +71°C) and non-operating (storage) temperature range. The battery’s performance characteristics, including voltage output and duration, are often specified across these temperature extremes.
Shock and Vibration: High-g shock events and sustained vibration profiles are common in launch, flight, and impact scenarios. The battery’s structural integrity and performance must be validated against these forces.
Altitude/Pressure: Performance must be consistent from sea level to high altitudes, impacting factors like heat transfer and sealing.
Humidity/Contaminants: Sealing against moisture and corrosive agents is critical for long-term storage and reliability.

Mapping Parameters to Application Classes

Different mission profiles dictate distinct thermal battery requirements:

Ejection Systems & Emergency Actuators: Characterized by ultra-fast activation and often short duration. The Ultra-Fast Activation Thermal Battery (28 V, <100 ms) is explicitly designed for such applications, delivering 28 V at 100 W rated power with sub-100 ms activation.
Precision Guidance Systems: Require stable voltage over a moderate duration (minutes) with varying load profiles, including significant pulse currents for control surfaces or data links. The 90 V Thermal Battery Series and High-Voltage Thermal Battery Series (100–150 V) offer the necessary voltage and pulse current capabilities.
Long-Endurance Munitions/Loitering Platforms: Demand extended operating life, potentially for tens of minutes to hours, with efficient power delivery. The Long-Duration Thermal Battery (28 V, 5800 s) is an example optimized for up to 5,800 seconds of continuous operation.
Micro/Miniature Systems: Where space and weight are severely constrained, micro-thermal batteries are essential. The Micro Thermal Battery (Φ13×28 mm, 13 g) provides 28 V nominal output in an ultra-lightweight, compact package.
High-Power/High-Voltage Applications: For payloads requiring substantial energy and peak power, such as advanced propulsion igniters or sensor arrays. The High-Power Thermal Battery Pack (>100 V, >5 kW) and High-Voltage Thermal Battery Series (100–150 V) are suited for these demands, delivering over 100 V and thousands of watts.

The Thermal Battery Selection Process

Define Electrical Requirements: Precisely specify nominal voltage, acceptable operating voltage range (min/max), average current, peak pulse current (with duration and repetition rate), and the total operating duration at each load condition.
Determine Activation Needs: Specify the maximum acceptable activation time. This is a critical safety and mission performance parameter.
Establish Storage Requirements: Define the required storage life (e.g., 10, 15, or 20 years) and the storage temperature range.
Characterize Environmental Conditions: Detail the full spectrum of operating and non-operating environments, including temperature, shock, vibration, humidity, altitude, and any unique chemical exposures.
Identify Physical Constraints: Define maximum allowable volume, weight, and mounting interfaces for the battery. For instance, the Micro Thermal Battery (Φ13×28 mm, 13 g) specifies its compact dimensions.
Review Standard Products: Cross-reference defined requirements against existing thermal battery series. For example, if a 28 V system needs 100 W power and <100 ms activation, the Ultra-Fast Activation Thermal Battery (28 V, <100 ms) is a direct fit.
Consult with GNC Tech: Engage with applications engineers to discuss requirements. Leveraging a broad portfolio, GNC Tech can help identify suitable standard products or explore custom solutions if the application falls outside standard offerings.

Preparing Your Thermal Battery Inquiry

To facilitate an accurate and timely response from GNC Tech, prepare a comprehensive inquiry detailing the following:

Required Voltage: Nominal, minimum, and maximum voltage requirements.
Load Profile: A detailed current profile over time, including average current, peak pulse currents, their durations, and repetition rates.
Operating Duration: The total required operating life after activation.
Activation Time: The maximum acceptable time from signal to voltage output.
Storage Life: The minimum required storage life in years.
Environmental Conditions: Operating and storage temperature ranges, shock (g-level, duration, waveform), vibration (Hz, gRMS, duration), altitude, and any other relevant environmental stressors.
Physical Constraints: Maximum allowable dimensions (length, diameter, width, height) and weight.
Interface Requirements: Desired electrical connector type and any specific mounting features.
Quantity and Schedule: Estimated annual quantities and target delivery schedule.

Providing this detailed information enables GNC Tech to recommend the most appropriate thermal battery, whether a standard product from series like the 28 V Thermal Battery Series or a tailored variant to meet unique mission demands. Export eligibility and compliance are reviewed per project during the inquiry process.