Batteries are nasty little hand grenades just waiting to blow if mishandled. I know, I had a battery blow up in a high school auto shop class when I taught high school. There fore I am very careful about "doing things by the book" and leaving myself a big margin of safety. I have seen other battery mishaps during jump start attempts, so I try to be careful, having seen another battery blow up due to open flames nearby setting off the explosive gas in the battery. Yes, you can get away with alot of marginal things, but sooner or later the odds will work against you. If you want to give yourself a small easy margin of safety, at least wear some eye protection when working on batteries. You ought to see how deeply an explosive battery can drive metal and plastic particles into your face. Not a real pretty site!!