I was amazed to handle a small battery of the type which seems to be causing all the problems. It was for a light a/c & was about 25% lighter & smaller than the current one I am using. Surely two larger versions for the 787 could not be a significant weight penalty.? Maybe the real problem could be the unusual all electric design of this a/c. There must be huge amounts of electrical energy being shunted around the wiring looms.