Sadly, the 10 seconds come from the theme. I originally wanted a smaller but automatically resetting timer but decided to against it as it would make it harder to implement the theme.
If I'm going to work on it after the jam (Which I'm not sure about because the program I use to autocomplete my code eats all my ram :( ) then I will change it so battery spawning is a bit more balanced, the timer being more visible and it giving you a "death" card instead of ending the game, similar to how getting hit with a bullet works.
I think those 3 changes will help improve the timer situation while still keeping the "10 seconds" theme alive :)
(Also, I think batteries can technically give you 0 extra seconds now, which I should really prevent from happening)