Yuasa is the battery manufacturer. They are an excellent battery manufacturer, possibly one of the best in the world. I am sure they will get to the bottom of it. Who knows what is causing it. Did Boeing spec the battery wrong? Did they spec the battery one way and then install it in a way that wouldnt work with how they spec'd it? Was it spec'd for a certain way to charge it, but it is being charged completely differently?
There are a ton of other questions to be asked.
I think there is a problem with grounding. These batteries are getting cooked. I think some of the high draw items will have to go back of the accessory drives. Hope I'm wrong because that won't be a quick fix.