I am building my own kite boarding jump height tracker.
It's an 9 axis IMU that calculates the distance of upwards accelerations to tell me how high my last jump was.
It has a display, an imu, a gps and a battery.
So far my plan is to 3d print a little housing, put the pcb in it and fill it up with 2k resin, to make it waterproof.
But I have 3 issues / concerns:
is it ok to put the battery in resin? I am a little bit worried, that it might expand and then build up pressure with the resin around it. Is there another solution?
is wireless charging the best solution here, or are there any other ideas, which i haven't been thinking about yet?
any suggestions on what switch to use, to turn the device on or off?
You can completely pot your components but look at both heat and the affect moisture might have on your potting compound. Make sure you use one that doesn’t expand with moisture and is rated to use with electrical components as some are corrosive. You can just create a waterproof housing and this is a common method in commercial products. Use an o-ring or seal around any openings. The good thing with this method is you can still get access to change batteries etc and you can test it prior to putting your electrical apparatus in it. Put a weight on it and dunk it in the sea to various depths to see how well it works. Try slamming it into the water in different ways to make sure it can handle dynamic pressures
And just to expand on @pmagowan 's ideas, look at dive shops for these types of cases.
They are not very expensive and are designed with submersion in mind. Turn it on at the beach and close the box. They are well sealed and yet easy to open when back home. You can then re-charge the battery, download data, etc.
Use a magnetic switch. Similar to a reed switch. Switch on the inside and magnet on the outside.
Addition:
If you are really serious about waterproofing, never, ever run wires into the enclosure. Water loves to follow stranded, twisted wires, into the enclosure. Temperature changes in the box will pump the water in through the wires.
You don’t need a waterproof switch. Just put the switch behind the cover where the battery etc is. You can get a water resistant one for double protection but the least amount of breaks in the shell is best.