Having third party suppliers, preferably authorized by the car manufacture, is essential for the long term survival of limited production automobiles if the dedication of the parent manufacturer is in doubt. Others have said this before re roadsters and many other cars. Not saying that Tesla will not be dedicated to supporting the roadster in the very long run but good to be t least discussing this issue.
That being said, a third party supplier of a battery is a complicated issue. First of all, the battery isn't going to fail within a year unless it was a considerably poor rebuild. The concern I would have is more in the selection of battery cells ( when the third party community reaches that level of refurbishing (beyond electronics and connectors, etc)). The choice of cells, how well they are balanced in capacity, the choice of positive electrodes (which are dynamic as the choice of transition metal ratios utilized in layered oxides are being revisited), whether the positive electrodes are coated, the choice of negative electrode, electrolyte, and especially electrolyte additives. On top of that, whether the ESS charging protocol is optimized for that very particular collection of chemistries. Also, how were the cells stored before assembling into the battery. Maybe I would take a shot with a third party for a PEM, but for a battery system, there would have to be a good decade of history for the company or a partnership with a major battery cell manufacturer before I would seriously consider such an option. Not worried about one year down the road, worried about five to ten years, even if I saved 40%. There is no reason why Li-ion batteries can't survive 15 years if properly managed and level of discharge is controlled. Regarding the other thread that was recently active, the impact of the roadster is clear, but the more amazing impact, even to those in the field, is the demonstrated amazing longevity of the 6.9k Li-ion cell ESS of the roadster. This is an amazing accomplishment by Tesla and they deserve much respect for their attention to developing a very impressive and robust active thermal control and power/charging system for the roadster. This and the motor, besides, the beauty of the roadster is something to be proud of and really established the foundation of the viability of EVs and demonstration that the batteries can last.
