i had an issue not long back where my fan belt had come off, so the car ran flat, however i drove the car last night all was fine, got up this morning to go to work and the car wouldnt unlock via key fob so had to manually unlock it and get in, turned the key but nothing, it was as if it was completley dead, i have an amp that is connected but i cannot see that draining the batery as its all wired up correctly, what else can cause the battery to drain over night???

 

lights etc were all off...

also the fan belt has been fixed, ( probably best to mention :D)

If the battery has been run completely flat they can struggle to hold a charge even overnight. No amount of charging would get mine to last anymore than a day so I got new one and all was fine.

If the battery is over a couple of years old, and you have completely discharged it, it would need a realy good period of charging to restore it to a capable working condition, or the complete discharge could actually kill it. Either try disconnection and a long slow charge or replace. Also find the source of your current drain when parked up as that will also kill the new battery if persistant.

if the boot is not closed properly the battery will drain

if the boot is not closed properly the battery will drain

 

will check it, but i am pretty sure its been shut properly