Rechargeable batteries are available in a very wide variety of devices. From cell phones to satellites we can find them anywhere. So, why don’t we see them more often in hearing aid applications?
One of the earliest rechargeable hearing aid batteries was handled by Unitron in the early 1970’s. The charger was a very nice small brown Bakelite case that could hold 2 #675 batteries and plugged directly into a wall outlet. It could provide a charge in 4 hours that would last for 8. This product disappeared as Zinc-Air batteries became more available and less expensive that the finicky Silver-Oxide or environmentally unfriendly Mercury batteries.
Now, some 35 years later Zinc-Air batteries rule the hearing aid battery market. There are some notable products which have rechargeable batteries as an option like Siemens and up to date information can be obtained from your sales representative.
This evaluation is based on the Power-One batteries and Charger. The Power-One rechargeable battery system can be used with any make or model of hearing aid, new or old. The Nickel Metal Hydride batteries that it uses have to be removed from the hearing aid and placed in the battery charger for its daily recharging, then replaced back into the hearing aid for use.
Supplier: Power One
Battery type: Nickel Metal Hydride (NiMH)
Voltage: 1.2 volts
Capacity: 20mAh (312)
Cost per cell: $9.95/each
Cost for charger: $100
Lifespan of rechargeable cell: The NiMH hearing aid battery is expected to last 500 charges, this translates into 16 months. If a hearing aid is expected to last 4 years it will use 3 NiMH batteries.
312, 13 = 12-16 hours
10A = 8-9 hours
675 = not available
The card charger is amazing and confusing. The card charger has a built in Lithium Ion battery. It is plugged into a standard house outlet and can charge both the NiMH hearing aid battery and the charger’s own LiON battery. When the LiON battery is charged the unit is now able to charge NiMH hearing aid batteries 18 more times without being plugged in. It can charge one or two hearing aid batteries at a time, and comes equipped with adaptors to fit 10A, 312, or 13 size batteries. Depending on charge condition, battery placement and other variables a sequence of pretty blinking lights will greet you. If you place the NiMH hearing aid batteries in backwards it blinks at you, and no apparent harm ensues.
Charge time is 3 hours. Batteries can be stored in the charger with no harm.
Pen Charger (aka Beagle Neuralyzer):
Very reminiscent in appearance to the Neuralyzer (memory eraser) from the movie “Men In Black”. I tried it on Benny the family Beagle and it did appear to erase his memory, but when I tried it on the kids it had no effect at all. Benny’s memory is spotty at the best of times, so the whole memory eraser thing is questionable.
It turns out that the blinking lights indicate that the NiMH hearing aid batteries are charging. When the red lights quit blinking the charge is complete. This product takes 2 AAA batteries.
Within the limits of time and demand, this product was not evaluated.
I ran 3 ads in the local community newspaper – circulation 55,000 and received no phone calls to participate in the trial of the product. We then tried the product on existing patients to get some feedback.
The Nickel Metal Hydride batteries look exactly like the Zinc-Air cells. This presents a small problem as patients and the clinicians had difficulty identifying which battery is which at a glance. As a result some non-rechargeable Zinc-Air cells have been placed in the charger (no effect noticed), and some $9.95/cell NiMH rechargeable batteries have been thrown out by mistake.
Maybe someday they will colour one of the terminals of the batteries to help distinguish it as being a rechargeable battery?
Impact on the environment:
The impact on the environment due to the disposal of zinc-air batteries appears to be grey. While there is a symbol on the back of each package of zinc-air batteries admonishing us not to throw out the batteries (or feed them to babies) there are no known facilities in North America that recycle them. It is recommended that they be collected and brought to a disposal terminal for proper disposal (burial).
Collection of Zinc-Air batteries can be easily accomplished by dropping them into empty 1 litre water bottles. We fill about 1 bottle a year at the office.
Over the course of a 4 year lifespan, a hearing aid using #312 zinc-air batteries will use 162 cells. This will cost a patient $202.50 ($1.25/cell). Using rechargeable NiMH batteries will cost them $195.00 (cells and charger with 50% markup).
One patient raved over the design and concept of the charger but was quite put out with the demands of removing the batteries to charge each night. (See Siemens for their product specific solution to this, it is quite nice).
Another patient never mastered putting the batteries in the charger properly – it is possible to place the battery in upside down, the lights blink, but the battery does not charge.
Another patient over the course of the one month trial threw out 3 rechargeable batteries and kept trying to recharge Zinc-Air batteries by mistake. We coloured the rechargeable batteries with red marker and that helped.
Other patients were quite indifferent to the product, and other patients were put off when they learned that the price differential was so low. (There was an assumption that rechargeable batteries would equate to cost savings.)
The price differential at this time is not enough to represent significant savings to the patient. The product evaluated also has the added difficulty of removing the battery from the battery door every night to place in the charger.
As for its impact on the environment, a patient will not be throwing out 162 zinc air batteries every 4 years for the traditional route. Going rechargeable will result in them throwing out 3 NiMH, and 1 LiON battery in the same time span. Not a great savings in volume discarded.
If a charger was available without the LiON battery this would be a step ahead.
Perhaps in the future rechargeable batteries will be coloured to prevent accidental disposal (confusion with Zinc-Air batteries as they look so much alike.