Hey there, my car battery keeps draining overnight Howeve...

Hi there I will do all I can to help. Seeing that the battery is brand new as well as the alternator I would have to think that your car has a parasitic draw somewhere. Outside temperature does affect battery performance but a new battery should be able to hold a charge at least overnight. First just to rule out any charging system issues check that with the car running you have at least 13 to 14.5V at the battery. To check for a parasitic draw you need a multimeter capable of reading amperage. What you need to do is disconnect the positive battery cable and connect one probe of the multimeter to the battery and the other one to the positive cable. Leave it connected for 10 to 15 minutes, make sure all the lights are off all doors closed the reading should be 0.05A or less, if not then you have a parasitic draw. If the reading is high, then what you need to do is pull fuses one by one until the reading goes down to less than 0.05A. whichever fuse makes the reading go low will be the system that is staying on. once you figure out which system is staying on you need to examine the wiring diagram for the system and start unplugging things on the circuit one by one to determine the cause of the draw.

But i dont have multimeter

Oh ok i understand, unfortunately that is the only way to find out what is going on with the electrical/charging system of your car.

Okay, thank you for your help.

No problem. Good luck!