New battery draining fast.

Why is my new battery discharging so fast? I have an old iPhone 11 I pulled out of a drawer to give to my daughter. It had been sitting in a drawer for the last 2 years and was completely dead when I pulled it out. I plugged it in and charged it. It charged to 100 percent but would discharge very quickly. Like within 24 hours while just sitting on the counter not being used at all. So I ordered a new ifixit battery and followed the installation guide. The replacement battery had no charge when I tried turning the phone on so I plugged the charger in. I let it charge overnight and by morning it only showed 47% charge. I left it plugged in while I was at work and came home to it showing a charge of only 30%.. I unplugged the charger and turned on a video at full brightness and let the battery discharge fully until the phone shut off. This did not take long, maybe 30 minutes. I then charged the phone overnight again. This time it showed 100% in the morning. I unplugged the phone and left it on the counter again while I was at work. When I came home it had dropped to 74% in spite of not having been used at all. I again turned on a video at full brightness and allowed the battery to discharge fully until it shut off. Then charged it overnight to 100 percent again. It is still discharging substantially while not being used, and even faster when in use. Do I have a bad battery? Something else?