Medical / Biology has it's own author order convention. First author is generally the person that did the most work/research on the publication. Last author is the person who managed it. Second author is generally the primary grunt of work. After that is anyone else that contributed / edited, often in order of amount contributed.
Source I worked at a research hospital for several years and actually managed to snag myself a second authorship on a project.
IMO the solution is to change it from charging the battery to swapping out the battery. The problem then is having a standardized battery configuration/connection and we all know how well standards go. The station can then charge for the electricity and expenses, including an amount to cover the occasional battery replacement.
The use of money is all the advantage there is to having money. -- B. Franklin