Changed battery, now different charge behaviour

Before if the battery drained fully, connecting to charge, the red battery indicator would show on screen and wouldn’t turn on until about 5%. Now phone turns on immediately and sometimes shuts down showing 1% then restarts immediately and stays on when gets to 2%

Anyone know why this is? I think its because the serial is different? So iphone is not managing it correctly. Can I code the new battery using something like JC V1S?