Xiaomi mi electric scooter 4 pro bhr5398gl July 8, 2019 16 32 64 128 Xiaomi mi electric scooter pro 4 black eu bhr5398gl Scooter xiaomi 4 pro Xiaomi pro 4 scooter review Scooter xiaomi 4 Xiaomi scooter pro 3 Xiaomi scooter 4 ultra test