BYD, QuantumScape, and EVgo could head higher once the EV market warms up.September usually isn't a great month to buy stocks. It's historically the worst-performing month of the year due to a wide range of factors -- including new bond issuances pulling investors away from equities, portfolio readjustments after the summer, and behavioral biases.But assuming that "September effect" happens again, investors should heed Warren Buffett's advice and "be greedy only when others are fearful." One sector that alr ...