So I have this car battery [View all]

It's been in a car that's rarely driven and is old so there are no constant electrical draws on the battery, and it's exposed to moderate temps, rarely below freezing, and prob not above 80 or 85. I charge it sometimes with a 600 milli amp lawn mower charger. Recently it didn't have enough juice to crank but a few seconds. The voltage reading is about 12.1-12.2 before attempting to start it.

But I put the battery in a modern vehicle and charged it with the lawn mower charger. I shook it too. Today it started. Now it starts normally, and the voltage reading is 12.21. Kind of common voltage here because not driven a lot, but enough to turn over a 4 cylinder.

But let me tell you the rest. It's a Kmart lowest end battery, Plus Start brand, made by Exide, and it was purchased in January 2010, manufactured August 2009. The sticker is still on it, and I have the paperwork.

Is the battery any good? Should I take it for testing at a big auto retailer?

16 years on a battery. My national chain other battery I bought 4 years ago is dead, this thing keeps ticking. So in the Great Recession did they use premium parts because that's all they had? Do I have exceptional quality I'll never see again?

Appreciate any insight. This is out of the ordinary.