Replacement for non hybrid battery in the trunk?

I my battery finally going bad? Yesterday my little brother was driving my mom around when apparently the car stalled in the middle of the street. The only thing my little brother noticed besides the car being more sluggish than usual is that the center console display turned white when the car stalled. He was able to restart the car and limp it home.

Torque Pro found codes related to the hybrid battery, which also needs work, but I noticed that the battery voltage for what I assume is the trunk battery rests a 9.6v when I turn the key to position two, but jumps to 14.1v when the car is actually running. Is this too much of a voltage swing meaning that the battery is bad? Do you guys have a recommended replacement?