Can I depreciate the remaining basis in a business vehicle (100% used for business- Bus for transport) if it becomes inoperable?

A new battery, and maybe it's as good as new.

Really not enough information here to come up with an intelligent answer.  So maybe you've come to the right place.  

 This is reply to your heading, but don't know about statement in the body of question. you may simply scrap an item because it has no further use in your business and has no resale value. When this happens, you treat the disposition as a sale for no money, which will produce a loss equal to the balance of the adjusted basis at that time.

It should also be noted that if it is "sold" for any value at all, that isn't Scrap. That sale is computed for Gain or Loss on Disposition.

You are not Depreciating; that is "we used up the value over time."

You are Disposing.

Scrap is a perfect example: the metal itself likely brings in some money, when something is truly scrapped.

Then, "donating" has different rules than "using and depreciating" and "selling for residual value."