I would put a trickle charger on it and see how it makes out.

 

The first thing I would do is check for battery drain. It could be something like the dome light staying on.

 

Lots of very short drives in subzero cold - not helping; the car never really gets a chance to warm up. Hope this isn't the original battery from 2008...
Does the car have auto lights/wipers? If so, leaving them in the "off" position seems to help battery life. May be as simple as a loose ground or corroded battery clamps - did the Autozone guys check those?

 

Mine starts fine in any weather, with the lowest being -16 degrees. Battery has 40,000 miles of usage (I like to count miles since I drive a lot).

Some of the very early 2008 batteries were problematic...that and after 6 years, should've been replaced anyway. How old is that battery?

FWIW - Just because the battery will charge doesn't mean it'll hold the charge.

 

If the car sets outside, a small solar charger may be enough to keep it topped up.

 

Thanks, all! I am going to take a look tonight and see if I can tell if it is the original battery. We just got the car a year ago and it only had about 12K miles on it

 

2008 only driven 12k in almost 6 years? I'd reckon original battery.

 

As I recall, there were a group of cars that were shipped with a battery that was too small for the 'comfort package' and the dealers were supposed to upgrade them to a larger battery. It is possible that yours got overlooked and the cold weather has made it show up.

A call to the dealer with the VIN should answer that question, not sure if they could do anything after this length of time, but you would know if that is your problem.

6 years on a battery is a pretty good run. especially in a colder climate.

 

With only 12k miles when they bought it, I wonder just how many times it's actually been to the dealer!

 

Your biggest issue is the 7 minute drive. The car never has enough time to recharge the battery. Plus if it is the original battery, with that low of miles, it's probably lead a hard life. Not using a battery is worse than driving it all the time. I'd say the battery is getting weak.

My 2008 had the comfort package upgrade battery put in back in 2009, it starts fine every morning. This morning it was -24. Doesn't turn over the fastest, but no car will in these temps. BTW, I just passed 150K, on my car, never let me down once...

 

Update - this time I wasn't even able to jump it. I couldn't tell if it was the original battery by looking at it, but as others said, it is a safe assumption. I am just going to replace the battery this weekend. Thanks for your input!

 

That's the right move, but if you ever have the problem in the future it would be best to get a battery tender plus if it's going to sit in sub-zero temps for four days without starting. A new battery you probably won't have that issue but later on yes. JMHO