Automated External Defibrillators (AEDs) are portable medical devices designed to deliver an electric shock to a person experiencing sudden cardiac arrest. These machines analyze the heart’s rhythm and, if necessary, guide a rescuer through the process of delivering the life-saving electrical therapy. The readiness of an AED is entirely dependent on its power source, making the battery a fundamental component of the device. Since AEDs are often stored unused for long periods, maintaining a reliable, charged battery is essential to ensuring the device can function instantly and effectively in an emergency.
The Standard Lifespan of AED Batteries
The lifespan of an AED battery is defined by manufacturers in two primary ways. The most common metric is the standby life, which refers to how long the battery can remain installed in the AED, performing routine maintenance checks, without being used for a rescue. For most modern AED models, standby life typically ranges from two to five years, though some high-capacity batteries are rated for up to seven years under ideal conditions. This duration is the expected time until the battery must be replaced due to natural chemical degradation and self-discharge.
Separate from standby life is the shock capacity, which measures the number of full-power electrical discharges or the total operating time the battery can provide once the device is activated. A new battery is often rated to deliver anywhere from 100 to 400 shocks. The battery must be powerful enough to run the device’s diagnostic functions and immediately deliver the high-energy shock required to restart the heart.
Factors That Reduce Battery Longevity
The stated manufacturer standby life is an estimate that can be shortened by various environmental and operational factors. A major power draw comes from the AED’s internal maintenance function, which involves frequent automated self-tests to verify the device’s circuitry and battery status. These automatic checks, which can occur daily or weekly, consume cumulative amounts of energy, gradually depleting the battery’s overall capacity over time.
Environmental conditions are among the most significant threats to battery longevity, particularly temperature extremes. Storing an AED in an environment that is too hot, such as a parked vehicle, accelerates the chemical reaction within the lithium cells, causing faster degradation and capacity loss. Conversely, very cold temperatures can temporarily reduce the battery’s discharge efficiency. Most manufacturers recommend storing the device within a stable temperature range, often between 10°C and 30°C (50°F and 86°F), to ensure optimal performance.
Monitoring and Replacement Procedures
Ensuring an AED is ready requires a proactive approach to monitoring its battery status, which is typically communicated through clear visual and auditory indicators. Most AEDs feature a status indicator, often a blinking light or a specific icon on the device’s display, which should be checked regularly for a green or “ready” signal. If the device detects a low battery or a malfunction during its self-test, it will switch to a red indicator, emit an audible chirp, or announce a voice prompt to alert the owner to the need for immediate replacement.
A maintenance log is an important tool for tracking the battery’s installation date and its manufacturer-stated expiration date, allowing for replacement planning well before the power runs out. When a replacement is needed, it is important to procure a certified Original Equipment Manufacturer (OEM) battery specifically designed for the AED model, as these are engineered to meet the device’s exact power and safety specifications.
Since the conductive gel on the electrode pads also degrades over time, it is common practice to check and replace the electrode pads simultaneously with the battery. Pads typically have expiration dates of two to four years.
Expired AED batteries, especially those containing lithium, should not be placed in regular trash and must be disposed of properly through local waste management or specialized recycling programs.