I received the standard key and the sports key with my car. Unfortunately the sports key died and I like the idea of having multiple keys. I decided I would have a go repairing it myself, here’s the story of how it went.

I found a load of the tutorials online of how to replace the battery by desoldering the CR2032 and then soldering a new one on and then either glueing the casing back shut or 3D printing a casing to enclose it. 

I decided to embark on the challenge. I’m a product designer so love taking things apart. I found the Techy bit of opening and desoldering the battery very satisfying and enjoyable. Quick test to check it works on the car, and my soldering skills were proven adequate. I then printed a generic casing from thingyverse and all was well. However, with access to a laser cutter, I decided to try to make it a bit more resilient, after all PLA breaks down in UV.

I started by laser cutting 3 pieces, a bottom, a middle chassis and a top. I then tapped holes on the chassis and assembled it back together. What I didn’t realise at the time, I’d now created a faraday cage… back to the drawing board.

I designed some 3D printed gaskets and assembled, hey presto it worked. Side note, 4mm spacer works, 3.5mm does not! Who knew such a small change would be an issue!? However as mentioned, PLA is brittle and breaks down in UV. Time to test further.

I printed it in TPU, a flexible material that can create a splashproof seal. No luck. Turns out TPU blocks RF more than PLA! I then decided to give PETG a go, it’s a harder and longer lasting material than PLA. And it worked! 

So I now have a working key, in titanium, with a replaceable battery holder! Next I plan to do the following to keep improving my design;  
\- add fuzzy edges to hide the layer lines on the 3D print  
\- design an exoskeleton (maybe 3D printed) to make it smaller and more funky  
\- create a silicon mould to reinstate the waterproof features and remove the 3D printed gaskets  
\- make a matching casing for the main FOB out of titanium

Follow the thread for updates 😄

My sports key/tag died :(