Why does my battery not hold a charge.

should have a little round sticker on the side of the battery with the month and year,like 03/10. or the month and year will be stamped out on top of the battery.about all you get out of batteries now is around 4-5 years? the battery really is just for starting the car,then the alternator take over after it's started,feeding voltage to everything and MAINTAINING the charge on the battery,not actually charging the battery,but maintaining the charge.first thing is to check all connections,clean(shines like new),tight,free of corrosion including GROUNDS! then with the car off,a fully charged battery should have 12.6 volts on it,checking with a volt meter.then with the car running,the battery should have 13-15 volts on it. you may have a battery drain,(something still on,still drawing power from the battery when car is off.copy and paste the link,watch the video.................................................................................................................................................... ..... How to Test and Find a Parasitic Battery Drain … www.youtube.com/watch?v=zdIKNnwEjIs