Electrician here. Have you checked if the existing wire is aluminum or copper?
It's quite common to run #6 aluminum instead of #8 copper for 40 or 50a circuits because of the cost savings.
If it is aluminum you'll need to use proper connectors to junction to copper but really if possible it's most likely the simplest to just run the 6/3 straight to the charger.
gottapoop t1_ir3od00 wrote
Reply to comment by Loon610 in Wiring EV Charger by Loon610
Electrician here. Have you checked if the existing wire is aluminum or copper?
It's quite common to run #6 aluminum instead of #8 copper for 40 or 50a circuits because of the cost savings.
If it is aluminum you'll need to use proper connectors to junction to copper but really if possible it's most likely the simplest to just run the 6/3 straight to the charger.