Battery wont stay charged

Either the alternator is not being energized with the key on, or the main wire from the alternator to the battery/starter is bad.
Have you checked output on the back of the alternator with the engine running ?

Check the alternator! It may be bad!

Your alternator isn't charging your battery so your car is draining the battery. Have auto zone test your alternator

Check the charging relay if working. You can find it in the fuse box which is either in the engine compartment or under the dashboard on the drivers side legroom.

Alternator ? is the charging light of your car stays on ?

If the battery is new, and you are sure it is ok, either the alternator is not charging the battery or there is something in the car that is using power when the key is off.
You could disconnect the battery at night to see if it stays charged, and-or have the alternator output checked.

the battery wont stay charged? if youre putting in a fully charged battery and your car runs, but then the battery slowly dies, the problem will be your alternator. the alternator is what maintains a car batteries charge. try replacing the alternator. hope this helps.

If your battery is older than 3 years and you live in an extreme warm or cold envirnment, chances are one of the cells is dead. You will need to replace the battery if it wont hold the charge. Also bring the vehicle to an autozone or advanced auto parts store and have them do a free diagnostic on the alternator and voltage regulator. If the alternator is bad then that could also be your problem where the battery wont stay charged. A rule of thumb is that if you replace the alternator you should also replace the battery so as to avoid the new alternator from working overtime to try to bring up the charge on an old battery. These auto parts stores can also do a load test on your battery to see if it needs to be replaced free of charge.

check voltage regulator

Replace the large wire on the back of the alternator,with a new one,it comes off the back to the positive side of the battery,leave the old one on the alternator.