It's been many years since I was involved in the 777 development, but IIRC, the RAT generator fed the battery bus directly - if they still had the battery bus they would have still had the RAT generator.
Looking at the FCOM, the RAT supplies the C1 & C2 TRUs, which power the capt & FO instruments and via them, the battery busses. I also see a note: “The main battery can power the standby system for a minimum of 10 minutes”, which isn’t much!
This should not have happened. Uncle Boeing is going to get more grey hair
I suppose there are two ways of looking at this: on one hand, that this shouldn’t have happened and is evidence of poor design (sorry
td) but on the other, that after a once-in-a-hundred-million-flight-hours level failure(s), there was enough redundancy/backup in the system to allow the crew to make a successful approach and landing, which is indicative of a very good implementation. I think I would side with the latter...