Unfortunately the supplier has told me there is no way they could guarentee a used battery. They are offering a new one for around $4,000 dollars and would give me a $500 discount if I opted not to take the used one. It seems to me that it is worth the gamble to take the used battery and then purchase a new one if need be rather than take $500.

Is there a way to check how many cells are still working? I apologize if my questions sound foolish I have not been able to find information regarding the topic. I am not looking to safeguard against all problems just hoping to take all possible precautions so as not to purchase a used battery that will last 2 days.