Here is what I did to replace dead batteries in my Phonak Audeo M-50.
I would first suggest to read this thread: Insight into the inside of the hearing aid. It contains a lot of usefull infos and photos
Strategy used: remove te dead battery from its plastic casing, slide a new one in place and
reconnect the 2 wires to the main circuit
1- Battery from this supplier:
2- Electrically conductive glue/paint. It is more paint than glue (low viscosity) but it works
Steps for the battery replacement:
1- Remove the receiver
2-Open the external enveloppe and remove the first half
3- Remove the second half
4- Using the heated metal tube, remove the flat battery casing sides. To disconnect the wires from the battery, I used a thin knife inserted between the wire and the battery.
5- Remove the battery from its casing noting its polarity
6- Insert the new battery in the casing with the correct polarity in the right place. It is critical. Be sure that the end of the wire is bare (no isolation)
7- Glue the first wire on the new battery and let the glue dry for a couple of hours. Repeat for the second side.
8- Place the HA in an owen at temp. 50-55 deg C for 24 hours. Note the glue will be conductive only when completely dry
9- Re-assemble and place in the charger until the green light stays on. Be sure that the charging contacts protrude enough for charging
Both HA work now as new.
When used for 15 hours in a quiet surrounding and connected to phone (left side) but no streaming, I get the following battery level:
Left 60% Right: 70%
So, repairing the first one is somewhat stressing but once the process is established it will be a lot easyer for the second one.
The device and parts are very tiny. Work slowly and take a lot of reminder photos.
Note the piece of wood and the rubber band that I used to hold the device when necessary.
Feel free to ask questions.
I hope many will successfully do it! Let me know…
Happy new year!
See the photos below