Battery Health monitoring via Tessie App seems comprehensive. Shows battery percentage remaining, capacity, range, charge cycles, comparisons to Tesla fleet etc . Assume it’s relatively accurate for 2nd hand market.
Yep, I love Tessie too. You’ll need to set up the car individually within the app to access. Otherwise on Tesla, I believe it’s in the service settings for current battery degradation. No history. Would like to think it’s something that is available to Non Tesla vehicles too!