I had some time this afternoon to take the cover off the dead battery out of the 2010 Impala. There is a bar that links the plates between the middle cells. It is brunt through. I hooked jumper wire across the break and the battery then has continuity. So I am wondering if there is a vibration issue effecting the batteries??? The car doe not have any vibration issues you can feel but maybe it is amplified up through the fender skirt to the battery box. I have some dense foam sheets that are maybe 3/8 of an inch thick. I think I am going to put a sheet the size of the battery under the battery to see if it makes any difference.