I had a similar problem after having the car for about 2 weeks. I got a system error message saying traction battery fault detected, performance reduced. Things got back to normal in a few hours and I haven't had any issues since then. I have not noted any performance difference. One difference I have noted is the degree of regenerative braking. It maybe a subjective feeling but I have noted that the amount of regenerative braking has decreased. Maybe it is just because I have gotten more accustomed to the feature over time I have owned this car.