Posting 1038 by "deptrai" shows how complex an electro mechanical braking system can be. It is I suspect a heavy power user, so instead of the Hot battery bus providing power to fire extinquishers & P1 standby instruments etc, all of which use little power, this backup source has to be meaty.
It would be interesting to know why the a/c to date has suffered circa 150 battery replacements? Low voltage?? In a way this is a more serious problem than the two fire instances, since no sane pilot would accept an a/c without ultimate back up power.
I can see the potential for a complete redesign of this part of the electrical system.