The ideal ambient temperature for a battery? In winter, but also in summer.
The ideal ambient temperature for a battery is around 20 degrees Celsius. It's the same with humans - our comfort zone for most is around 20C. Therefore, great heat or extreme cold should be avoided. In the warm season or when the sun is strong, it is best to park in the shade. In winter, you should park your e-car in a garage, parking garage, or at least a carport protected from the wind.