I use a "battery tender plus"....On the P-car, I just placed it on the garage floor, it's leads coming out of the barely opened hood, set so the trunk light didn't come on. I just left it hooked up until I wanted to drive the car. Fully charged batteries don't freeze. Also, a fully charged battery is much easier on your voltage regulator and alernator. In other words, they live longer if you use a battery tender. In my detroit iron, I've used red top optima exclusively. That reminds me...now that I have a Mustang, gotta check which red top optima fits best for after the factory battery dies.

For the early P-car, I used a pair of "exact fit" Sonnenschein gel cell batteries.

Connect a float charger permanently to the vehicle/battery. Connect to ground (any metal part of the chassis) and to an active (always ON) fuse position (typically no. 1), but confirm with a test light or VM with engine OFF.

Before you drive off, remember to disconnect the power cord to the wall. :)

Sherwood

Another concern
 

I had an acident and it cracked my battery (not an Optima). I neutralized the acid with baking soda but five years later my front susspension mounts were toast. The water I used to do the cleanup ran down into the hollow space between the gas tank support and the suspension pan and continued to do its thing. If you didn't wash any acid down into this space good, but if you did I would consider running more baking soda and water through this area. Good luck