Actually, it might. Doing so would be the same as one of the popular 'tests' to see if the alternator is working. People will disconnect the battery while the engine is running, to see if the alternator is working. It's not good to do that, but ....
Alternator's produce more power as rpm increases. So at idle they don't always produce enough to keep the engine and other stuff working. A common example is stopped at night in the winter with wipers and heater going.
