I doubt it applies to any branded product. Why would anyone put their
name on an inferior product, no matter where it gets sold. In fact
most "store brand" are basically the same as the branded product. I do
agree Walmart does bring in a lot of junk to hit a price point but it
generally will not have a brand name on it that you have ever heard
of.
In the case of batteries, Johnson Controls makes Walmart batteries and
they have their name right there. Since there are really only a few
companies that make batteries under hundreds of brand names they tend
to just be commodity items. You can use the warranty as a guide to
quality but the battery I just replaced was a Walmart "2 year" battery
and it was 10 years old. I probably could have nursed another year out
of it but why bother? It was in a truck we seldom drive so it needs to
be able to hold a charge. It was a little sluggish turning over after
sitting about a month and I decided it was time. I did manage to get
the truck started but it was one of those miracle starts where it was
either going to fire or start clicking ;-)
The thing I like about Walmart is if you do have a battery fail within
the warranty it is a no hassle return. I think you could take one in
with a bullet hole in it and they would give you a new one.
(For Walmart, that night not even be unusual)
Used to get a kick out of the ads and perceived great reputation of the
Sears "Diehard" batteries. They are nothing more than a Johnson
Controls battery and previously Exide batteries, depending on who Sears
contracted with.
Again it is still all about the warranty. Sears was as good as Walmart
about a no questions asked replacement. One of my old Md buddies used
to use Die Hards in his drag racer. It did not even have a charging
system. He ran them all weekend on a single charge and throw it on the
charger before the next weekend's racing. Sometimes he ran them flat
down. They did not last long but he just threw it on the counter at
Sears and they gave him a new one.