checked the battery voltage with my volt ohm meter

Question:

I have a 2006 Pontiac Grand Prix 3800 series III V-6. The problem is this. About 3 weeks ago I took the car to my local Wal-Mart for an oil change. I came back to pick up the car and I was told by the tech that he had to jump the car to make it start and he suspected a bad starter. He could not define exactly why he thinks it is a bad starter. Since then the car has started every time every day except I have noticed that about 3 times now the information for date and time are off and I have had to reset everything. Finally this morning the wife calls me and said it is dead. I have checked the battery voltage with my volt ohm meter and have 12.4 volts. Under load when I try to start the voltage drops to just under 8 volts. Also, I noticed just opening the door to get into the car the voltage dropped to 9.99 volts. This car has 54K miles on it. Could these guys have hurt something jumping the car or would it be that I indeed have a bad battery or worse yet a starter issue.  Already Tried: Tested battery for 12 volt. 12 volt is present until I try to start. Voltage drops to under 8 volts. 

Answer;

This is a classic description of a bad battery. Put in a new battery and all will be good once more. The battery volts should not go below 10 volts under load.