The alternator does not hold a charge. It charges the battery. If it will not charge the battery then either the alternator is defective, battery is defective, or the connections are corroded or loose. You should read 13.5 to 15.5 volts at the battery with the engine idling. Check it with a DC volt meter. If you get less the alternator is defective. If you get much more the voltage regulator is defective.
It sounds like the alternator is bad. If the alternator is bad the battery will not hold charge when running
If your battery doesn't hold a charge while running then your alternator is bad
if its a new battery then you need to replace your alternator. It basically recharges your battery while the vehicle is running.
to make a quick check -- start car - disconnect the positive cable at the battery as it is running - if car stalls the alternator is bad if it stays running the battery is probably too weak to hold a charge. (daddmac)
Weak alternator, dead cell in the battery, or something is on pulling power from the battery when the cars is not running.
Inside the alternator
if a battery has a bad cell it wont hold a charge, but it could also be the alternator or the plug, i had a problem with the plug and had to change it from a junk yard, but before you do that i would check the easy parts first i.e the battery,then the cables, then the tension of the alternator belt, and finally the alternator itself along with the pigtail get a volt meter and test the current while the car is running, if it reads 13 to 14 volts the alternator is working and if it reads bellow 12 it is the alternator or plug. aojedamCheck your battery, it might be worn out and not able to hold a charge from the alternator.
Here is a test u can do to see if Ur alternator is good or not . when car is running disconnect the negative battery terminal it's the black wire.If car stalls then the alternator is bad if it doesn't stall then it's Ur battery is bad and u have to replace it
Symptoms: Besides having a dead battery.......... If you charge or jumpstart your vehice's battery and successfully get it running to only have it mysteriously die and have no lights, radio, etc.; it is probably you alternator. If your vehicle will run constantly on it's own, but will not start after shutting it off, it could be your battery. If your battery will hold a charge on it's own, but goes dead a while after you start and run your vehicle, it is probably your alternator. Or, if you can get it running, it should have an alternator light that will come on when there is a problem. I would almost bet your car has one... my 1970 ford does.
Your battery is bad, your alternator is bad or you have a wiring problem.
If the battery is less than 2 years but doesn't seem to hold a charge
Has the battery been tested, does the alternator on the Durango try to charge?... If the truck runs with the battery but the battery doesn't take or hold a charge, it has to be the battery being bad or extremely bad terminals so that the charge can't reach the battery. Age of the battery doesn't matter, a fairly new one can still go bad.