Really, that simple? Unless you have first hand knowledge about the issue how did you come that conclusion? What if the issue is with the electrical system, short or something? What then? stop smoking that Seattle Ganja!
Few things are as easy as the appear in an aircraft. Changing batteries will require review of design basis documents, altering calculations, weight loads, power loads heat loads and review and impact on associated equipment space and any other basis in design documents. Hopefully during prelimnary design they would have identified alternates. In short it wont be as easy as replacing an oriniginal car battery with another model / make. But it will be done, that is for sure. I would not venture to say the time, type of requalification that will be involved.
It is interesting that when a similar problem happened with the Cessna Citation the emergency fix was the replace the Li-Ion with Ni-Cad batteries without any other modifications. FAA reference: SB525C-24-05