Battery dead now

Checked battery voltage at 12.48v after sitting for one-day. Run 25 miles on highway today after jump start and stopped at Autozone, battery voltage is only 12.75v. Still could not start, even no response to remote key to lock/unlock the doors. Previously when starting showing delay, running on highway for 20 miles can get the car started very quickly by one turn of the key.

Now it is time to get a new battery right before the long & cold winter comes.

Thanks for comments/advices.