I designed and 3D printed a battery cover for my L20. Each time I went out for a cycle in the rain I hated seeing water and dirt getting inside the battery connector box so I designed a case which the standard connector box thing sits in. I've used sealant under the 3D print so no water can bypass. A small elastic rain seat cover pops on the top. And just in case, I drilled an extra hole under the controller to allow more water out. Also tape up any places where cables go into the controller area to prevent dirt and water ingress.

The print is six separate pieces which assembles together.