mutiple choice with multiple selection, multiple X values in pie chart

Hi all,

I'm new in the platform and would like to explore several capabilities of this platform.

Currently, I have issues in trying to manage the following issues:

I want to be able to log multiple Serial Numbers of my battery used for an operation. (3 is used at 1 time) Hence, I could only create 3 different fields for [Battery S/N 1], [Battery S/N 2], [Battery S/N 3]

hence in my multiple choice, there are several options.
E.g
001
002
003
004
005
006
007

When I try to build up a pie chart, I could only choose the X- axis to either be [Battery S/N 1], [Battery S/N 2] or [Battery S/N 3]. I want to be able to build a pie chart which can evaluate the total number of hours used by each battery so I can have a clear understand which one would require maintenance, etc. 

Additionally, I would want the system to prompt to my homepage whenever a Battery S/N reaches 50hours for example, how do I go about doing that?

Would appreciate any help asap!

Thanks.