Your starter solinoid goes: click,click,click,click,click,etc,,,,,,,and your alternator doesn't charge the battery back up.
Seroiusly, I found this out years ago, when I put a rear battery
mount in my street rod, and kept having to jump start the car
whenever I wanted to get it out. Found out the ground was loose, and there is where you actually pull most of the amps on a starter, the ground side. You've heard the saying,,,IT TAKES TWO TO TANGO,,, the same goes for good contacts on the negative and positive connections.