Why is it if i empty my bladder in the middle of the night after several hr (lots), i can still go again in the morning with another large quantity?

Possibly normal: Drinking large amounts of fluid in the evening May cause the symptoms you're describing, especially if your frequency and amount of urination is normal during the day. Try limiting fluid intake in the evening If your daytime urination is also excessive, and or, frequent it could be a sign of other medical conditions and you should consult with your primary physician.

Urine production: Many factors can influence the quantity if urine that collects in the bladder, including state of hydration, medications, diuretic effect of some foods and beverages, presence of diabetes, body temperature, incomplete bladder emptying. Having a full bladder on awakening is not necessarily abnormal, even if you emptied your bladder during the night.