dc to dc converter rosak?
oh no.

ev car dont need to service oil every 6 month interval, but it need 12v battery replacement every year or so 

Which car will give indicator that 12V is running low?

Tesla uses LFP batteries right as their 12V battery ? Not the normal standard battery which gives such problem.

Chief you are correct. The correct 12V battery for EV is completely a different construction type, just like you have mentioned earlier deep cycle because it's application in an EV is completely different from an ICE. It was my mistake to assume it's the same based on what others had written because it's not listed on my Principal Battery Listing. When I go to HQ I will enquire further about this to reconfirm everything.

No wonder Tesla is said to be using a 16V battery as claimed by some but online some claim it's 12V battery. I got no Tesla, so I cannot confirm about it's voltage 12V or 16V. What is clear is that those who are using the normal 12V battery meant for ICE in an EV, will definitely be running into problems earlier. Question is whether it's within warranty or otherwise.

About the high CCA, that I am not sure cause I have not got a chance to monitor an EV yet.