What's the best thing to ask sellers to do so I can check the battery condition?checking battery condition is instead the most important thing. It's hard to tell the real condition just from the CAC or where it charges to; though that likely sets a good lower bound. As long as seller does not pull a trick like charging in Range mode and then switching to Standard mode and letting you think it's a Standard charge.
What's the best thing to ask sellers to do so I can check the battery condition?
I think this advice applies to the Model S, not the Roadster. There are no "versions" of the battery, and the only electronics difference is the stereo. Road noise may vary if the car comes with a hard top.Battery version, electronics, road noise, fit and finish (interior and exterior), warranty, use or abuse.
Two easy checks are the ideal miles after STD charge and ideal miles after Range charge. For 50,000 miles anything north of 165 standard ideal miles and 210 ideal miles in range mode is good.
This is not an accurate way to measure battery health because the miles can vary depending how the car is charged. My car will reach 183 miles when charged at 240V/30A, but it will reach 190 miles at 120V/12A. The CAC is the most accurate measure of battery health. If you can't get that, then at least check how the car was charged to reach the "full charge" miles.
I agree with most people's opinions here - also getting a well-used roadster is probably better than getting a garage queen. My first roadster only had 500 miles on it and it had a lot of problems because the
previous owner didn't drive it enough to notice them - leaks in the trunk, major rattles, whacked out sensors, etc. and although everything was covered under warranty, the car was constantly in the shop.