Geez! 2nd time in my life a battery had shorted internally.
Installed a brand new Interstate from Costco (lowest price by far) to replace the 11 year old lump. 3 days later, No interior lights... tester showed 12.6v, checked/inspected connections, grounds, tugged on fusible links, blah blah.
Tested battery 3 more times with 2 different testers- 3.8v? 11.5? Weird; got it load tested @ the parts store formally known as O'Irish something... Fried cells! Hope the new exchanged battery lasts!

 

That's a bummer.

I bought a 6 month warranty lawn mower battery from Costco that just gave up after 2 years. I'm a big advocate of using Costco/Sam's Club for batteries and tires.

 

Most batteries are made by Johnson Control and rebranded

 

Or East Penn, just depends which side of the Mississippi river you're on.

 

i live in wisconsin(johnson controls is from here) and the Farm and Fleet and NAPA battery lines are east penn

Then there is also other makes too. but that requires a google because I cant remember which corporations bought which corporations and which are still their own thing