I parked my 2013 Model S P85 to go shopping and it had 140 miles on the battery. When I returned a half hour later the battery had gone to zero and I was unable to do anything. I had to have my $100K+ care towed to a Service center. I was told that the HV Battery showed a cell imbalance and it had to be sent to Fremont for a refurbishing. Is this a known or common defect? Also what exactly does this mean? My car showed no signs there was a problem before it went to zero.