Precision micro-hole for extended life batteries
Various embodiments of the invention provide an enclosure for a metal-air battery assembly for an extended wear hearing aid. The enclosure includes a diffusion control element having a dimensional property configured for controlling oxygen and moisture diffusion into the metal-air battery assembly to maintain a minimum battery voltage when the hearing aid is operating and worn in an ear canal of a user over an extended period. In an embodiment, the enclosure can comprise a shell with a base end having an opening therein forming a cavity within the shell and a base cap for covering the opening of the base end. A diffusion element is disposed on the base cap. In an embodiment, the diffusion element comprises a laser drilled precision micro hole having an aspect ratio of least about four and a diameter in the range of about 10 to 15 microns.
1. An enclosure for a metal-air battery assembly for an extended wear hearing aid, the enclosure including a metal shell having at least one hole therethrough and a polymer membrane adjacent the shell for controlling oxygen and moisture diffusion into the metal-air battery assembly to maintain a minimum battery voltage when the hearing aid is operating and worn in an ear canal of a user over an extended period, wherein the polymer membrane has compressed and non-compressed regions with the non-compressed regions aligned with the holes in the shell to control diffusion.
2. The enclosure of claim 1 , wherein the shell comprises a base end having an opening therein forming a cavity within the shell and a base cap for covering the opening of the base end.
3. The enclosure of claim 2 , wherein a plurality of holes are disposed on the base cap.
4. The enclosure of claim 1 , wherein the voltage is in a range from about 1 to 1.3 volts.
5. The enclosure of claim 1 , wherein a current drain at which the minimum voltage is maintained is in range from about 40 to 175 μA.
6. The enclosure of claim 1 , wherein a current drain at which the minimum voltage is maintained is in range from about 40 to 90 μA.
7. The enclosure of claim 1 , wherein the holes comprise precision micro through-holes.
8. The enclosure of claim 7 , wherein at least a portion of the hole is curved, or non-linear.
9. The enclosure of claim 7 , wherein the hole is laser drilled.
10. The enclosure of claim 7 , wherein the through-hole has a length to diameter ratio such that the gas ingress into the battery assembly is substantially diffusion controlled.
11. The enclosure of claim 7 , wherein the through-hole has a length to diameter ratio of at least about 4.
12. The enclosure of claim 7 , wherein the precision micro hole has a diameter not greater than about 15 microns.
13. The enclosure of claim 1 , where the non-compressed portion has a substantially circular shape.