Battery looses charge overnight/alternator charging?

Testing with battery disconnected may not give good results, condition of battery could still be questionable regardless of age. Battery going dead overnight usually indicated either a parasitic current drain, or defective battery. Remove battery and return to place of purchase to be charged (slow is best) and then load tested to evaluate it's condition. If that goes well then you need to have the load when off evaluated such as bad diodes in the alternator allowing it to discharge battery ( possible to do test with a voltmeter set for AC volts, connect to the battery terminals while vehicle is running at 1300-1500 RPM. Want to see less than.5(point 5) VAC). If that is good then something or some system is staying on after key removal, I.E. Glove box light, brake lights, autolight controler, vanity mirrors, etc. Staying on pulling battery down. Do whaat you can and let me know back if you need further instructions.

Thanks I will do that. Douglas