Hearing aids rely on a steady supply of power, typically provided by zinc-air batteries, to function optimally. These specialized power cells use oxygen from the surrounding air to generate electricity, making their performance unique compared to standard alkaline batteries. Testing their power level accurately prevents unexpected device shutdowns and helps determine if a perceived malfunction is simply a depleted battery. Knowing the battery’s state can prevent unnecessary replacement of a device that is otherwise working correctly.
Quick Checks Without Equipment
Before using specialized tools, simple checks can determine a battery’s condition. For a newly activated battery, ensure the zinc-air cell has had enough time to “air up” after removing the protective tab. Allowing the battery to sit un-tabbed for one to two minutes is necessary for the voltage to reach a functional level.
The most common method for testing a battery already inside the hearing aid is the “sound check.” Cup the entire hearing aid tightly in your hand with the compartment closed and hold it near your ear. A working battery generates sufficient power to cause acoustic feedback, resulting in a distinct squealing or whistling sound.
A quick visual inspection can reveal problems that mimic low power, such as moisture or corrosion. Look closely at the battery surface and terminals for signs of swelling or white, powdery residue, which indicates leakage. If the battery appears compromised, dispose of it safely and do not insert it into the device.
Testing With Dedicated Devices
A precise assessment of battery power requires specialized testing equipment. The simplest tools are compact, dedicated hearing aid battery testers, which often use a conductive sled or slot. To perform the test, place the battery onto the contact points and slide it, completing a simple electrical circuit.
These testers typically feature a screen or analog needle indicating strength using categories like “Good,” “Fair,” or “Replace.” The display measures the battery’s ability to deliver current under a small load, providing a more realistic performance measure than a simple voltage reading.
For the most accurate measurement, use a digital multimeter set to the DC voltage (VDC) setting. Set the meter to a low range, such as 2 volts, since a new zinc-air battery operates around 1.4 to 1.45 volts. The positive (flat) side must contact the red lead, and the negative (rounded) side must touch the black lead. A reading in this range confirms the battery is fully charged.
Understanding Battery Life and Test Results
Interpreting numerical results requires understanding zinc-air battery chemistry. A reading of 1.4 volts or slightly higher confirms the battery is fresh and fully activated. This high-power output is maintained for most of the battery’s life, which is characteristic of zinc-air technology.
The voltage stability is followed by a sudden and rapid drop-off in power toward the end of the functional life. A battery reading of 1.3 volts is not slightly depleted but is nearing its end point. Hearing aids may signal a low battery or cease functioning entirely when the voltage dips below approximately 1.31 volts.
If a battery tests well above 1.35 volts but dies quickly inside the hearing aid, the issue may relate to the device’s high power demand or improper storage. Modern hearing aids with wireless streaming or advanced features place a significant load on the battery, draining it faster. Improper storage, such as keeping batteries in high humidity or extreme temperatures, can also prematurely reduce capacity, even if the open-circuit voltage initially appears strong.