Seal broke down after 3 days

New BYD Seal broke down after only 3 days with a LV Protection System Fail - contact main dealer. BYD Assist sent the AA who had a look at it , checked the 12v battery and thought either battery fault or DC to DC converter fault. He sent for recovery wagon which eventually took it back to Dealer. Dealer tried new battery (removed from another Seal apparently) No Joy. Waited for a new Control Module (presumably the DC to DC Converter) then for some other Tool that was required to become available. Easter got in the way of course so now still waiting after 1 month. I am hearing some stories about the 12v batteries not being charged often enough from the Main Traction battery especially on the long journey from China. Anyone else heard of this? Beginning to get really fed up now. We have a loan car which is OK but not very economical. Automotive Industry