Here is a link to a video showing the shell of a Linx Quattro being replaced. At 2:33, you can see the grey “latex” sealant on the battery compartment. You can also see that it looks like a standard replaceable battery compartment, with the grey sealant applied and molded to fill the space.
What I know:
a) Generally, IPx8 ratings are not achieved by sealing the case (and as you can see this one is NOT sealed), but rather by sealing all the electronics with a waterproof/hydrophobic coating and the encasing the physical contact junctions with water tight connectors (such as SureFit 2).
b) The main reason the batteries are not user replaceable in IPxx devices is because the end user cannot do so and ensure the integrity of the IP68 rating. Which makes sense from a manufacturer perspective. If you want the manufacturer guaranteed performance, you use manufacturer certified techs to do the work.
c) The cell under the sealant absolutely looks like a standard button cell.
What I suspect:
The “latex” coating over the battery (described above) exists ONLY to seal the battery/contact interface so the instrument can achieve the IP68 rating.
What this might mean:
If you’re a disposable user, who is used to not having a water resistant instrument, it is quite likely that one can carve out the sealant, drop in a compatible rechargable cell, and repower the RE561-DRW at home much faster and cheaper than sending it back for repair.
Disclaimer: I am geek/hacker by nature. I void warranties, often on brand new tech. Plus, my HAs did not come with a warranty. Please consider your risk tolerance and the potential expense before following in my footsteps.
Mine worked just fine. And the empty hole is large enough to accommodate the receiver wires backwards without unduly bending them.