battery

I am going to be changing the battery in my Corvette soon. A quick couple of questions for the group, Usually I keep my battery tender on the car side of the cables when I pull the battery to keep some power going into the car so I do not loose any of the memory or settings. Is this the right...

So today I started my car normally, it hesitated just a bit but didn't mind it. Went to the gas station and after car refused to turn over. One of my headlights went out and all sorts of random stuff was going on with the electricals everything went haywire. Got it jump started and it works now...