Our 17 Jeep batt died strangely in Sept 23. We had been rough back roading in Wyoming all day, got to a highway Scenic View, rested a few min, then no start! I roll started the jeep and thankfully town was just 6 mi down the mountain. We rolled into O'Reilly with fingers and toes crossed! They brought out their tester, ~9V!, very sad. They took the battery out and put it on/in their battery test cabinet. TEST, Suddenly +12V! A miracle recovery?! I asked him to test it again and just as he pressed the test button I kicked the cabinet down low setting up a vibration, the test machine went bonkers, 9, then 12, then 13, then 9v.(I wish I could do that to slot machines!) A corroded bad cell in the battery. This was just a normal stock Mopar battery. I think the plates just happened to line back up momentarily putting out 12V for the test, but when I kicked the cabinet the failing cell shifted again, shorting out internally. We bought a GEL type battery. This was the original battery, so it was ~5+ y/o, I'm not complaining! Batteries with bulged sides are questionable, over 3 years old?, I have ZERO faith. In 40 years of cars I've had a brand new battery die in a week and I have had a used battery I pulled from a car I was scrapping function for about another 8 years. Batteries are plastic boxes full of lead, acid and mysteries. JK!