Hi mjmpyramid. Welcome to the forum. Normal procedure is to connect the positives of the dead car and the charger or donor car together at the battery posts, then connect the negatives together last. If you're using another car for a jump start, the recommendation is always to make the second negative connection to the engine or body, ... Someplace away from the battery. Batteries give off hydrogen gas which is explosive. The two cars will have different system voltages so there will be a small spark when the final connection is made. You want that to be away from the battery.
When using a battery charger, it doesn't matter if the negative cable is on the battery post, the engine, or the frame. They all go to the same place. Just don't turn the charger on until the final connection is made. The advantage, again, for not connecting right to the battery post is to keep potential sparks away from the battery.
Of bigger concern is why is the battery going dead overnight. Also, sparking at the negative battery cable when you wiggled it suggests that connection should be cleaned and tightened. A dirty connection will also prevent it from being fully charged while driving.
Tuesday, April 20th, 2010 AT 3:13 PM