nissan 300 zx

[sdriver73]

ive a 1990 nissan 300zx and for some reason the battery keeps going flat ,ive replaced it with a 30%more power type for the car but over night it goes flat ,i can jump it and it starts up fine and runs well but as soon as i stop the battery goes flat

[funkymoped]

sounds like youve got something permenantly live. could be an interior light (glovebox or under bonnet/boot) thats staying on after you switch the car off.
i wouldnt have thought it would be anything more. if you had something running to earth, it should blow a fuse.

[qapmoc]

The only way the battery can go flat so quickly is that something is taking power when it should be off, obviously if it was something like the headlights left on you would see it. The most probable cause is the alternator is faulty and is staying in circuit when it should not be. try disconnecting the cables (usually one large and one small) that connect to it overnight then see if it starts OK next morning.