Stop in for a cup of coffee

So, my POS truck didn't start yesterday at work. 14° and sat 10hrs. A friend with a new Chevy tried to jump start it, nope. Got a Co-op to join in. So, new Chevy and an older VW jetta TDI at the same time, took a bit, then finally lit. I am so very tired of this.... Maybe a bad battery or cell? His new truck was pulled down to 9V when I was cranking!