Wasn't that also the most pressing limitation on the Apollo 13 recovery too? That and the unholy cold of course.
Actually the fundamental problem on Apollo 13 was lack of (electrical) power. Everything else was a direct or indirect result of the fact that Apollo 13 had lost the ability to generate electricity and had to rely on the LEM batteries. Even the CO2 problem was because the Command Module had lost electrical power (aside from the batteries which they need to save for re-entry), and the lithium hydroxide canisters from the Command Module didn't fit the LEM (requiring the Rube Goldberg setup to use square canisters in a system designed for round ones).
It wouldn't surprise me if this sub is faced with the same problem - they can survive until the battery's give out.
Here's hoping they can be rescued before then.