As in go check yours! I put new batteries in my truck just a few months ago and took a lot of time to clean up the bus bars, take apart the cutoff switch (which is a known failure point on my particular truck), use dielectric grease on all of the connections, etc. I took my time and did the job right. They were tight.
Yesterday my truck wouldn't start. New starter 6 months ago. I fired up the APW and it is charging batteries, but they were showing 12.7 before I fired up APU. 13.4 while running so no problems with APU alternator. Hmmm.
I took my cover off and reached up from the ground to start my truck and got a spark show! Jeez, scared the crap out of me. EVERY one of my 8 lugs on my batteries was barely finger tight. Apparently they will rattle loose. I'm thinking of adding lock or star washers to them this weekend and I'll definitely be adding tightening them to my regular PM list.