Eddie, you can get a lot of really helpful advice from the Cherokee
Pilot's Assn - consider joining it.

I don't normally check the battery myself except for annual since it's
a sealed battery. If yours is a wet cell with caps, the fluid level
should be checked monthly and refilled with distilled water. There's
supposed to be a drain at the bottom of the box. And many owners who
fly up north add padding/insulation to cut down airflow from the back.
The PA28 door seals are poor, and air flows out through the door and in
from the back of the plane.

You can also find a lot of useful information on getting a good door
fit on the CPA chat site.