Insight into the inside of the hearing aid

So funny you mention this. If I wind up returning my M50 for battery replacement (unlikely since I haven’t for so long) I will mark the internal frame in some manner to hopefully answer that question. I think @tenkan noted he was an engineer and suspected the battery can be swapped. He is probably correct. At some point they will be doing battery swaps and the actual hearing aid model will have long been out of production.

@BeLo That leads us to your expertise. Knowing that they need a battery that will be off-the-shelf years after the hearing aid model production has ceased would lead me to believe they have used something they suspect will be available. Any thoughts on how we could match measurement data from @sterei scans to readily available batteries ?

You could just look at the serial number in Phonak Target and see if you get back the same serial number.

Oh Yeah; I see your two nubbins now. I don’t know what to think about those?? Might be to use a tiny spanner to rotate the case counter clockwise a little in order to dislodge the case from my two nubbins and then easily remove the case. But I’m just guessing?



Yes, you can rotate and cut to see inside. PM sent.

I think these “nubbins” two are marks from the injecting tool’s pusher. These are pins used to push the part out of the mold after the plastic part was injected.


Unless the pictures are misleading it looks to me like a metal button cell inside a plastic housing.
It also looks possibly spot welded directly to the enameled wire leading to the rest of the device.

I’m intrigued that it appears to be in a metal casing as this reduces the charge available for the given volume of cell so there must be some beneficial trade off, probably safety but maybe something else

I’ve had a look around based on those measurements and a couple of things struck me:

  1. There are readily available (RS Components) Lithium based rechargeable button cells, I couldn’t immediately find any matching our criteria but since they exist and are manufactured in quantity it wouldn’t be too difficult for Phonak to have them custom made.
  2. It looks like a tight, if not impossible, fit, but there is a battery called a 400909 that might be a suitable replacement. Lithium cells are a bit ‘squidgy’ so it might work, example: For Earphone Camera Video Pen Mini 3.7V lipo Li Polymer Rechargeable Battery | eBay

It’s more than likely that there’s a Chinese website out there with the exact replacement part but it will take a bit more digging.

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This page says it could be a 13. It’s possible a rechargeable Lion battery exists. 7.9mm x 5.4mm You can buy size 13 rechargeable NiMH on Amazon.

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It was on the FCCID website.


Wonderful post.
I have Paradise Audeo P90R’s. It’s good to see what is inside.
And now I understand how to charge my batteries…the routine is important. I won’t run them dry.

Thanks for your post.


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Thanks so much for your information. I’ve had to reset my hearing aids twice. Taking them out of the recharger, the light was solid green An hour or so later one hearing aid was dead. I had to reset the hearing aid and charge it fully to use it. I wish I had 312’s, but the rechargeable hearing aids are great otherwise. (I have a workman’s comp claim for hearing loss due to noise).

I have Phonak M50R. One of the batteries is dead after less than 2 years of use. Since I got the pair on Ebay, nobody want to repair it locally. Hence, I would be very happy if you could share info on how to open it to eventually replace the battery.

Many thanks

Very interesting to have a CT scan, but what would he even better is to know how to open it without destroying the case.

For the KS10 I noticed that there is a metal pin that’s holding two halves of the case together. Maybe I would try to pray it open when it’s out of warranty.

I’m pretty sure we can identify the exact part number for the rechargeable battery.

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Very interesting. This engineer greatly appreciates you posting theses images!!!

agree with yoyomin’s comment about how to open

I’m still with the Marvels, not the paradise, but I’d imagine mostly similar…and I’m not rechargeable
what I have been most curious about is cleaning…and specifically the microphone ports
how likely is lint/dust etc to collect in the opening?
where is stuff like accidental or careless overspray from sunscreen on bug repellant going to land?
what materials are “exposed” to better understand chemical compatibility issues?
is gentle blowing with compressed gas logical?
rinsing with something…perhaps alcohol?

Alcohol damages the casings of the hearing aids so likely the same with Mic ports etc as well.

I’m an engineer too, and once worked at a lighting control company. One thing we did was to test wall plates with Formula 409 (not sure it’s available outside the US). It’s a popular cleaner, but it seems 409 includes some chemical that is particularly hard on plastics, so stay away from it. I’d use mild soap or diluted dishwashing detergent.


Well that’s depressing.

Finally got around trying to open my KS10. Pretty straightforward process. Remove the receiver and push out the metal pin at the bottom. Lift the case from the bottom side and push the case upward and they should come apart.

The battery is in a plastic holder. I can’t quite make out the writing on the battery: Li-Ion on first line, and “t(c) u 8(B)5(S)” on the second line?


Very nice and interesting pictures.
Thank you for sharing!


Yes very good pictures, yeah it’d be good to ID those batteries.

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Can you tell if the battery wires actually pass through the circuit board or if they are just soldered on to the top?

From the photos and the size of the globs of solder it looks to me like it’s just manually soldered to the top of the board on both sides. It would just be a case of de-soldering and then reapplying a conformal coating when soldering in a replacement.

My unreliable audi recently told me that the actual hardware cost of an HA was $100, if remotely true then the battery replacement procedure would need to be pretty straightforward to be economically logical.
Maybe more than just the battery is swapped out for the in-house replacement procedure to make it easier for a technician?

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There’s text visible under the plastic, so looking hopeful.

Yeah but it’s pretty hard to make out with that plastic cover, plus I don’t think the wire would be going right through, it would be lazer soldered in some way to the battery.