My wife's car has a marginal battery now. It's been through quite a bit since I got it. The current battery is a Die Hard Weatherhandler that I got in October 2010 for $55 + core fee. It's actually kind of amazing how long it's lasted given what it's been through. It does start reliably as long I don't listen to the radio too long. I was waiting for my wife in a Costco parking lot. I then tried to start it and it died. I forgot I had a jump starter (and it's kind of old anyways) but I went to the tire center and was allowed to borrow their jump starter with a Costco card and an ID left behind. I know it wasn't because the battery wasn't charged when we left home, because I literally hooked it up to a charger at home before leaving.
I'm kind of wondering why one of the most common applications isn't covered by Costco with their current Interstate private label battery with the 42 month warranty. In the past they've had Kirkland Signature Group 51. I bought one years ago and got it replaced for free because it wasn't working too well under less than 2 years. I think it was less than $50 when I got it around 2008-9. My wife leaving the map lights on may have had something to do with it, but eventually I changed all of them to LEDs, which extends how long it takes to completely drain the battery. Costco does have Group 51R, which seems kind of odd given there are probably more cars around that need Group 51.
The other thing I've seen is Pep Boys has a "ValueGrade" Group 51 where it says $26.32 after promotion, but I don't know if they even have it anywhere. I get nothing when I try to see if any store has it. It just stalls. It may not be great, but if I could get it for that price I don't care.https://www.pepboys.com/product/details/662040/00815
Almost anything else I can find seems to be over $100 now. Batteries Plus Bulbs has a Duracell (I think East Penn) Group 51 for $120. I think AAA batteries are East Penn. All the auto parts stores and Walmart are over $100. Walmart doesn't have ValueSelect Group 51. Sears has it on sale for $113. My Sam's Club membership expired years ago, but even they had the Duracell for $100.
About the only one I can find that seems reasonable is the Deka 551MF from Lowe's. The shipping to a store may take a couple of weeks, but I can live with it since the battery still starts if I don't drain it with the engine off. I'm wondering about the "farm equipment" category, but 551MF corresponds to what East Penn says is the right battery for my wife's Civic.https://www.lowes.com/pd/Deka-12-Volt-560-Amp-Farm-Equipment-Battery/50183737