I have had some bad luck with some "Kirkland" batteries I have purchased.

I have returned the one that I bought for my Chevy Silverado twice, I'm on my third now-so far so good.

Then, this past week, the one I got for my 2dr, in May, also crapped out. It was okay for several stops and starts on Monday, then, while driving, I noticed my horn wasn't working, so when we got it home, my grandson and I, went to work on the problem. Eventually we replaced all the wiring that ties the two horns together
and got them to work, but when we went to put the car away the battery was completely dead. We hadn't left the key on or the lights etc. Then yesterday, after letting it slow charge (2amps) for 4 or 5 days, I went to start it-nothing. I took that battery back but did not get another one. The good news is that Costco refunds the full purchase price, even more if the price went up, no questions asked so that is okay.

When I replace the battery, I'm thinking of getting a WalMart Maxx, actually top rated this month in Consumer Reports in the Group 35 size, I'd like to be sure there's not a fault somewhere else in the car. Are there simple tests that can locate a battery leak using a voltmeter? If yes and you are willing to elaborate, please be specific as I am electrically chalenged but can use a voltmeter to some degree.