My car battery drains its power when I try to start the car even when fully charged what could cause this?

Replace the battery if it's older than 4 years.

If you were able to charge the battery then drive to work or wherever, and then not start after shutting it off, it may be your alternator is not charging (maybe it charges enough to not make the idiot light come on) your battery would not have recharged as you were driving. You may have bad connections at either the battery terminals (even though they look clean and tight they may not be) or bad connections at the other end where it attaches to engine (ground) or solenoid (to starter). it could perhaps be the solenoid itself.

If you have changed the starter and have tested the battery (a good battery lasts about three years on average) have the alternator output checked, it should be about 13-15 volts.

There are too many things that may cause this to happen and I apologize for the vagueness of the answer...but these would be the things to check

Though you may have an alternator problem, it sounds like there may be more than that. If you put a new battery in and you only get one start before it goes dead?. You should get more than one start on a new battery. If the battery is bad then it wont hold a charge, but you said you put a new one in and it did the same thing? Some ting is causing a big draw on the battery. If you do get the alternator checked, you do not need to remove it. They will be able to tell how many amps when its running. Good luck

I would say if the battery gets a full charge and the lights come on strong sounds like the battery is fine. After one drive to where ever and the battery is drained sounds more like the alternator is not working and so instead of charging the battery when the car is running and feeding the electrical components of the car, its all on the battery which drains it pretty quickly.

Test to see what the voltage is of the battery when the car is off and when its on. it should be 12 or so off and 14.3 or so on.

Sounds like you have a problem with the alternator not charging SOME of the time. If a diode is going out, it can drain the battery almost immediately.

Of course when it's working, it will check that it's good. I'd replace it. If it doesn't fix it, take it back for a refund, but if it does...smile and think kind thoughts about my answer.

after starting the car with a week battery turn the celing light on.. and rev the motor it should get brighter.. if nothing happins the alternator is bad... the car will run on the battery but the alternator or generator has to recharge it.. take the alternator off take it to pepboys they will test it free.. also check the belt if it has a lot of slack it is not turning the pully.. clean the battery terminals and the posts.. i am shure its the alternator... also make shure there is a wire hooked to it that is in good shape when you take it off.. ok

Have the battery load tested. Check all cable connections, especially to the ground. Also have the starter amperage draw measured. If you have any after market accessories tied into the battery, like a stereo system or amps, disconnect them. You have a short circuit and they can be hard to find.

I would have the alternator tested. If it checks good, then I would say that you have a short somewhere. Or a bad battery cable.

It is the alternator. Your alternator recharges your battery once its started, and because yours is bad, your fully charged battery has all its juiced sucked out while the car is started.

The alternator. It will drain your battery like that.