If the car is not driven often (not just started) you may need to get a trickle charger. The electronics are supossed to go to sleep mode after being turned off, but I do see a lot of Mustangs come in here to the dealership with dead batteries. Most do NOT get driven and the batteries just get weak.

Motorcraft batteries are the best you can get, and I would recomend getting one. (100 month warranty) A bigger CCA battery will not give you more start power. A battery will ONLY use what it needs. Buy smart, get a charger and it will start every time for years.  

Thank you, I think the battery in there now is the motorcraft should i just get the same one? what about the Optima series batteries? If i disconnect the battery during the winter will that help prolong the life of the battery?

optima red top FTW.  lots of people have trouble with the motorcrap battery.... luckily mine is still good after 3 yrs  

Red Tops FTW 

the red top optimum batterys are awesome i have that on my stang what i do in the winter time i disconnect the negative battery and when i go to start it i just hook the cable back to the battery and starts up everytime.. if u leave it hooked up and not starting it, it draws the battery down .. u should try and disconnect the negative cable and u should be fine. 

That will help keep your battery alive, but on newer cars it will also not let the car record and hold the keep alive memory. That will cause other problems.  

The s197s are nortorious for this ! Has happened to me a lot. I'm not sure if it's an design flaw or what.My battories are high output / High end Audio battories furnished by XS Power Master and they do the samething.

I have one of these on my car. If only charges if the battery gets low then shuts off.

http://cgi.ebay.com/ebaymotors/New-Battery-Charger-Tender-Junior-Jr-12V-75A-DELTRAN_W0QQitemZ220486273604QQcmdZViewItemQQptZMotorcycles_Parts_Accessories?hash=item3356018a44 

I have a Battery Tender also ,Once I hooked it up,that was the last time I had a dead battery.I bought one from Summit Racing  for $40.00. Scott

thanks for all the help. new battery plus tender should be good to go. 

Its not just with your 07. I have an 05 Stage 3 Roush, and my battery started goin dead the 1st winter that I had it put away. Its not a trickle charger you need, its a battery tender. I actually mounted mine under the hood, hard wired it to the battery, and ran the plug down near the center facia opening. you cant see it at all, and it works great. It doesnt overcharge it, and as long as you keep it plugged in when ever you dont drivie it, it will keep that battery good. Mine ends up lasting about 1 week then if I dont leave it plugged in. My battery is good, I had it tested. However, I am going to be picking up one of those new red top six pack batteries mentioned by a few others here.