The truth is slowly coming out. Boeing have admitted to circa 150 early battery changes, mostly I suspect as they were down on power. If you recall there was an incident just before the battery fire problems of a braking problem, low backup power maybe? Also other electrical problems with refueling valves, again would these have been caused by errant battery power problems? as refueling is often done with out the full electrical system being powered. As it would be impossible to retrofit the brakes with a hydraulic accumulator as fitted to other a/c types, maybe the way ahead is to double up on more reliable older style batteries. Yes it would add weight, but at least the a/c would be flying.