Changing 36V battery to 48V affect my ebike 36V hub motor?

Hi, I recently just started riding an E-bike. LICI Z1 36V lithium battery 36V 13A speed controller 36V 250W hub motor. I would like to upgrade to 48V battery, ( 36V lithium + 12V Sealed Lead Acid Battery, connected in series) And it am also planning to change my speed box to 48V 18A. Will this be compatible with my 250W motor? Will I burn my motor? Current speed is 25KM/H. What would the change with 48V speed controller and battery be like? Please advise. Thanks.