A Letter From Katy Pindzola of Ear Technology as Promised, on Humidity and HI Batteries - From the Horse's Mouth !

[Guest guest]

From mail moments ago, verbatim, from Katy Pindzola, of Ear Technology

Dear Bob,

It was great to talk with you today. As we discussed, the subject of leaving

batteries in or out of hearing aids during Dry & Store conditioning continues to

come up, so I’m providing our most current information to you. I’d like to think

that we can help clear up some of the confusion.

Confusion seems to persist, in large part, because for so many years the advice

given by battery manufacturers was to remove batteries before placing hearing

aids in any kind of drying kit. However, in 1998, Energizer conducted tests and

found that 1) leaving the batteries in hearing aids during Dry & Store

conditioning did no harm to their zinc air batteries, and that 2) under high

humidity conditions, Dry & Store conditioning can actually help extend battery

life.

Rayovac continued to advise against leaving the batteries in, until just

recently. In July 2003, however, the following appeared in an interview with

Denis Carpenter, the Zinc Air Technical Manager at Rayovac, published in

Audiology Online:

“A dry aid kit may be beneficial for your battery, however, if you normally

use your aid in a high humidity environment. The drying that occurs in the dry

kit can counteract any excess water intake due to the humid environment that can

shorten battery life.”

So it appears that Rayovac is, like Energizer, acknowledging that leaving the

batteries in can be beneficial.

A key point to remember is that the ear canal is a relatively humid place, even

more so when the ear canal is blocked by a hearing aid, thereby trapping the

moisture that our bodies’ skin naturally releases all day long, even before we

ever *break a sweat*. Certainly that process is hastened when we’re physically

active – i.e. perspiration. Or take the case of a BTE, positioned at the

hairline, with sweat – excuse, me, perspiration – streaming down our heads. (I,

too, admit that on many occasions, I have been known to go from *glisten* or

*glow* to real honest-to-goodness sweat.)

Another point to remember is that the Dry & Store conditioning cycle is 8 hours,

then the hearing aid battery is back in use. Most likely the thinking behind the

longstanding instruction to remove the batteries is that zinc doesn’t perform at

its best when super-dry. But the drying process occurs between periods of

hearing aid use, and the Dry & Store conditioning process is more like a warm

spring day in Phoenix (95-100øF at 15-20% RH), not mid-day in Death Valley. Our

belief is that overnight Dry & Store use removes the residual moisture that

adversely impacts electrolyte balance, bringing the battery back into its

nominal operating environment, after which it’s re-positioned at that humid

location in the ear or behind the ear.

Battery manufacturers are working to engineer batteries that operate in high

humidity because of the ambient (warm, humid) condition of the ear canal, to

maintain performance requirements of high-power demand hearing instruments,

while also accommodating active lifestyles of hearing aid users (read *more

sweat*). Nonetheless, extreme levels of humidity can have two effects: the zinc

compound can become saturated with moisture, thereby reducing its efficiency,

and moisture droplets can actually block the tiny hole that lets the air into

the zinc air batteries (which in turn causes the interaction with the zinc

compound to produce energy).

Here are excerpts from relevant articles:

by Denis Carpenter, Rayovac Corporation, Zinc Air Technical Manager

(Audiology Online)---Dry aid kits create a low ambient humidity

environment which causes the cell to lose water. Assuming that when

the aid was in use, no significant loss or gain of water from the cell

has occurred, (emphasis added) putting your battery in a dry aid kit will dry

out the

cell and shorten battery life. This difference in life would be most

noticeable if your typical service life is more than 10 days.

A dry aid kit may be beneficial for your battery, however, if you

normally use your aid in a high humidity environment. The drying that

occurs in the dry kit can counteract any excess water intake due to

the humid environment that can shorten battery life.

Here’s an excerpt from an interview with Norm , Technology Manager and

Business Development Manager,

Energizer Batteries published in Healthy Hearing, February 2003:

HH/Beck: Please tell me your thoughts regarding battery driers and hearing aid

driers?

: We have researched this a couple times. We've tried to determine whether

or not dry aid kits do take the moisture out of the hearing aids if stored in

them overnight, but more importantly, to see how batteries are affected by the

dry-aid kits. Our results show the hearing aids do dry out a bit in the dry aid

kit and, interestingly, the battery life is usually improved if left in the aid

or placed in the kit with the aid. These tests were run on hearing aids in a

very moist, humid environments for 12 to 16 hours per day, and then placed in

the drying unit over night. So yes, the dry aid kits work, and they are worth

using on a regular basis. The electric units may be more efficient over the long

run, but we haven't compared passive (silica gel) versus electric dry aid kits.

From an article in the Hearing Review by Karl E. Strom, April 2004:

…But the fact is that zinc air is one of the most advanced battery

technologies

available. As one of the chief engineers at Rayovac has pointed out, if

it

were not for those pesky little air holes in zinc air batteries [which

supply

the oxygen], zinc air technology would be the most widely used battery

type

and would even be more popular than alkaline batteries. Zinc air is

almost

the perfect battery *except for the holes.*

The holes, while supplying the oxygen that powers the battery cells, also

activate the battery once the tab is pulled off. Additionally, zinc air

batteries are more susceptible to the climate, incurring a slightly

higher

risk of drying out or of being affected by moisture. In fact, the latter

is

coming to the attention of hearing aid battery manufacturers who supply

product to the worldwide market, especially to Africa, South America,

and

Southeast Asia, where the tropical climate can tax zinc air technology,

according to . In extremely humid environments, as well as in

third-world

applications where a battery might be rationed and used for as long as a

month, water can be absorbed into the zinc air cell. This can lead to

the

battery shutting off, or in worse-case scenarios, corrosion, bulging, or

rusting of the cell. While not a problem in the Northern Hemisphere,

says

Energizer and other companies are starting to recognize this and tweak

their

designs to be more tolerant of these environments.

In the last excerpt, Mr. notes that high humidity is *not an issue in the

Northern Hemisphere*, yet so many folks who rely on hearing instruments are

operating those hearing aids and processors in high humidity environments – and

not just in tropical zones - that can easily mimic tropical climates, by virtue

of condensation (going in and out of air conditioning, for example) and active

lifestyles that generate perspiration and contribute to humidity levels inside

the ear canal and inside the hearing aid. And, as noted earlier, moisture on the

skin can easily migrate to the case and inside the case of a BTE hearing aid or

processor as well.

As an aside, I’d like to give you the background on our involvement with the

battery life issue. When Dry & Store was first introduced in 1997, our

instructions followed the existing protocol. We said to remove the batteries.

However, we started to receive comments from Dry & Store users who *admitted*

that they had not removed their batteries and seemed to be noticing longer

battery life. That was when we asked Energizer to test the impact of

conditioning on zinc air batteries, and we subsequently changed our operating

instructions.

So the two major battery manufacturers now agree that it’s OK to leave the

batteries in, and battery life, independent of hearing aid type, can benefit

when used in a high humidity environment. Additionally, while the preceding

information addresses battery life as a standalone function, because such a

large number of Dry & Store users have continued to report dramatic increases in

battery life, we think it may also be due to the combination of functions –

drying the hearing aids as well as drying the batteries: greater efficiency of

the electronics when not impeded by moisture, improved battery contact points

due to corrosion prevention, and simply because it takes less energy to drive a

dry hearing aid than one that has diaphragms saturated with moisture.

Bottom line: the *generally accepted practice* relative to removal of zinc air

batteries is reversing its course…which is good news for hearing aid users who

no longer have to fumble with tiny batteries to remove them prior to

conditioning. I can’t speak to other hearing aid *dryers* as I don’t know their

operating temperatures and conditions, but we’re confident that Dry & Store

conditioning does no harm to zinc air batteries and in many cases, can improve

battery life.

Please let me know if you have any questions. Also, please let your list members

know that we welcome their questions and comments; they can contact us via our

website (http://www.dryandstore.com) or by email at info@.... Thanks

for giving us the opportunity to be of service.

Best regards,

Katy

=============

A. Pindzola

Manager, Marketing & Project Development

Ear Technology Corporation

P.O. Box 1017

City, TN 37605-1017

ph: 800-327-8547, 423-928-9060

fax 423-928-0515

“Dry & Store®. Better Hearing through Better Hearing Aid Care.”