Hearing aid battery Information Mike Day 10 October 2008 mikeday at backwater dot com Hearing aid batteries have been standardized to five zinc-air models. These include a color code on the packaging and the zinc-air battery pull-tab. All modern hearing aids use only zinc-air batteries. Silver-oxide and mercury-oxide batteries are no longer used. Mainly because they don't have the power density of zinc-air. In the case of mercury batteries, there is the additional concern of toxic waste disposal issues. The following five batteries are the current standard hearing aid batteries in use: Color Type Chemistry ( IEC/ANSI ) Volts Impedence Red Tab Size 5 zinc-air (PR63/7012ZD) 1.4V 10 Yellow Tab Size 10 zinc-air (PR70/7005ZD) 1.4V 16 Orange Tab Size 13 zinc-air (PR48/7000ZD) 1.4V 7.5 Brown Tab Size 312 zinc-air (PR41/7002ZD) 1.4V 7.5 Blue Tab Size 675 zinc-air (PR44/7003ZD) 1.4V 3.0 Battery Volts Impedence Life Load End Size 5 1.4V 10.0 Ohms 33 mAh 6000 Ohms 0.9V Size 10 1.4V 16.0 Ohms 90 mAh 3000 Ohms 1.1V Size 13 1.4V 7.5 Ohms 290 mAh 1500 Ohms 1.1V Size 312 1.4V 7.5 Ohms 150 mAh 1500 Ohms 1.1V Size 675 1.4V 3.0 Ohms 600 mAh 620 Ohms 1.1V Special use hearing aid batteries: Special zinc-air batteries for high power use Battery Volts Impedence Life Load End Size 13HP 1.4V ? 250 mAh 110 Ohms 1.05V Size 312HP 1.4V ? *160 mAh 220 Ohms 0.9V Size 675HP 1.4V ? *250 mAh 620 Ohms 1.1V *50% duty cycle HP=High power use (eg cochlear implants) For use in body style hearing aid: Battery Chemistry Volts Impedence Life Load End Size AA carbon-zinc 1.5V 0.2 Ohms 1000mAh 60 Ohms 0.9V Size AA alkaline 1.5V 0.2 Ohms 2500mAh 60 Ohms 0.9V Previously used obsolete battery Battery Volts Impedence Life Load End (IEC/ANSI) Size 41 1.4V ? 390 mAh ? 1.1V (PR43/7001Z) Alternate silver-oxide batteries available: Size 13 *silver-oxide Size 312 *silver-oxide Size 675 *silver-oxide *silver-oxide alternate chemistry available in this package, but is no longer used as a standard battery in hearing aids. They are however used in devices that benifit from the long shelf life of silver oxide batteries. Silver-oxide is not available in size 5 or size 10. Obsolete hearing aid batteries: These batteries are obsolete, no longer being made, or no longer used type numbers. Type 41 - mercury-oxide and silver-oxide Type 76 - silver-oxide (type 675 size) Type 230 - zinc-air (replaced by type 10 battery) Type 164 - mercury-oxide Type 132 - mercury-oxide Type 502 - mercury-oxide Type 401 - mercury-oxide Type 500 - alkaline ----------- The main advantage of zinc-air is a high power to size ratio (higher even than currently available lithium batteries). This means that for applications such as hearing aids, zinc-air lasts longer than any other battery technology currently available for the application (2x to 3x longer than silver-oxide). The negative for zinc-air is a very short life once activated (2 months typically). And a short shelf life (two years) even when not activated. For hearing aids, this fits the normal use pattern and is acceptable where the battery is normally used up from a few days to a week or two at most. For most other applications that short duration is not acceptable. Zinc-oxide has a relatively stable output voltage of 1.3V to 1.4V over the life of the battery. Mercury oxide and silver-oxide batteries are the other chemistries previously used in hearing aid batteries. Mercury-oxide is no longer used. Partly because zinc-air lasts longer, but also because of concerns about toxic waste issues. In many countries, mercury-oxide batteries are no longer allowed. The advantages of mercury-oxide is a long life when not in use. Mercury-oxide also has a very stable voltage output over its life (1.35V). The voltage only starts to fall off when the battery is used up (10% life remaining). Because of the long self life and stable voltage, mercury batteries found use primarily in applications such as cameras. Before the advent of the zinc-air battery, mercury-oxide was the battery of choice for hearing aids. Silver-oxide batteries have similar characteristics to mercury-oxide. The main difference is a higher run voltage (1.55V) and a slightly shorter operating life (about 20% less). Silver-oxide replaced mercury-oxide as the battery of choice in applications that require long shelf life and stable voltage output (as is required for light sensor meters in cameras). Although lithium batteries are now replacing silver-oxide as lithium-oxide lasts longer.