It depends.
With a Shearwater you can go to the voltage page which give a much better idea of the battery state, especially if you’re noting the battery voltages on each build. SAFT batteries suddenly drop and this doesn’t show up on the battery "gauge" widget.
Of course if the computer failed, you’d just swap to one of your backup computers.
If the AI battery failed during a dive it’s a little inconvenient on a rebreather and not a reason to call the dive. AI is somewhat more important on open circuit, hence many would back up AI with a visible SPG