this is an 2009 car 12 volts alternator says charging 13.x volts but battery goes dead after 4/3 days of stand by and the battery is brand new
Parasitic Draw Testing | EricTheCarGuy.
also check to see if your brake lights are sticking on. a faulty brake light switch will cause this. sometimes it is intermittently
How old is the battery? It would be a good idea to have it checked.
Check places light bulbs might remain on, like in the glove compartment, trunk, under the hood, etc. A faulty alternator could be the culprit as well, esp consider this if you’ve been giving or receiving jump starts. And make sure the case of the battery is clean. Sometimes electrolyte gets on the battery case and that produces a current drain.