I had this happen to me last winter. The car was running fine, I pulled in to get some gas, and it wouldn’t turn over when I tried to start the car. Plus all the console lights slowly faded out.
I popped the hood and found I could twist the battery cable. It had worked itself loose probably from thermal expansion/contraction due to heating and cooling. I tighted it up and the car started ok. Later I took off both cables, cleaned up the connetions. Anybody can do this, but you need a special $1 terminal cleaning tool from Harbor or any car parts store.
Sears auto (at least they used to do this) has a free service where they’ll check your battey. No charge – no pun intended! Seriously, they’ll recharge it first, then check it with a load test. Then you’ll know if you need a new one or not.
Batteries cost anywhere from $50 to $150 or more. Check Consumer’s Reports. They have a battery article once a year or so. The best value battery – according to CR – comes from differrent vendors depending on the type of battery your car uses. I’ve had good luck with CostCo batteries and while a little more expensive, Sears batteries have proved good for me too.