Why iPhone battery percentage & battery health drain so fast after updating to ios 16.3.1??????

I was really excited when I want to update to ios 16 in September 2022. But after updating, my battery health suddenly drop to 99%. At this time I'm still ok because just 1% drop. On 1/12/2022, battery health drop to 98% after 1 year using 13ProMax. Then, it's still ok. Yesterday (28/2/23) I checked my battery health ady 91%. What the heck is this?! 7% drop within 3 months? Really disappointed with latest ios. Then, I decided to update to latest ios version (28/2/23) which is 16.3.1 since I read positive comment regarding battery drain. Last night before sleep, my battery is 90%. After 2hours (10.24PM) charging, 10% battery drop even I just use it for a while before sleep (12.30PM). When I woke up, battery drop to 73%. 17% drop while sleeping . Screen off also drop so much. Now my battery just have around 40%, I don't think it can last until the end of office hour (5.30PM). I'm not using my phone. I used whatsapp web during working hours. Ios 16 is the worst for me. Not sure how long my battery health can last at 91% if I need to charge twice a day. I really concern with my battery health because it's not cheap to replace it. I bought my phone for almost RM6k, this is how apple appreciate their users?! Before this I used 8+, my battery health after 3 years of using it is still above 90%. I really missed the old iphone which have a long last battery. Before updating to ios 16, my battery can last for 2 to 3 days for 13ProMax. Please solve this problem. Really frustrated with apple now.

[Edited by Moderator]