In my experience it’s none other than Walmart. That is, assuming that you have a Walmart with a car care center.
My first experience with Walmart’s auto service was when my wife and I were moving across the country and broke down in front of a Walmart that had a service center. We were first blessed to see a tow truck driver in the restaurant parking lot that gave us a jump start and would not take a penny. He directed us to the adjacent Walmart where we got a battery in record time. It only added about an hour to our week long journey.
About 2 years ago my battery died without warning. I got a jump start and drove over to Walmart to get a battery and it all went well. Fast forward to today when my battery once again died. I got it jump started and took it to Walmart where they replaced it with their “total replacement guarantee.” This is why I recommend Walmart as the best place to buy a car battery. In some instances an automotive repair show will give you a prorated value for your battery. For example, if the battery lasted 2 years and it was a 3 year rated battery, they would credit you for the third of the price which remained. Frankly, I am not sure if they make money on their batteries but I guess they count on selling other services, not to mention the fact that you can shop while you wait.
Kudos to the team at my local Walmart for getting me back on the road!