Can an apple pencil case affect its battery life?

Hi there,

I'm a little bit worried about the way my apple pencil is behaving. I bought a silicone case for it in order to protect the tip and feel it less slippery while writing. However, I've noticed that with the case on it the battery life is longer than without it, but so it takes longer to charge with the case on it. It is kinda weird. I'd like to know if this problem may be caused by the case (I think that's too ridiculous), or something else may be happening.

Thanks in advance.