Just wondering what this "frosting" on the Ni-Cd battery cap could be? How is it created? Is it dangerous? Should it be removed?

Check the pic below.

 

When the batteries are overcharged or even more when reverse charged, the vents allow electrolyte to escape. It means there will be reduced capacity to some extent.

 

When the batteries are overcharged or even more when reverse charged, the vents allow electrolyte to escape. It means there will be reduced capacity to some extent.

Aaaaaa, excellent. Thank you very much!