My battery is just a week old ...

Modern cars have parasitic drain from all the computerized control. It requires systematic approach to identify the myriad of potential causes. Eliminate any aftermarket devices which includes any plug in power supplies. After market radios, security, and remote starters are notorious parasitic drains.

How fast does the battery drain to a level that it no longer cranks? You need to verify it's recharging properly. Most auto parts stores do this diagnostic no fee.

If overnight then it's a gross drain. Over a couple days then it's a moderate load. If several weeks, it may be normal.

If the battery goes dead overnight with a 80mv drain you have a bad battery, the radio, clock and ECM along with other electronics all draw a small amount of current in order to keep their memories.

Do you mean that it goes dead after sitting a week or goes dead after a week while driving it?

sounds like a bad battery or a bad connection

are you putting the dead lock on when you lock the car as using this will drain the battery. also there is an external alarm fitted when it fail to keep charge it will use the battery power. they are prone to catch fire so would check this to.

Yes Charlene,
If they didn't buy the correct wiring adapter, And instead cut and guessed which wire did what. The same hot wire for the dash lights goes to the radio too,So you can dim them all. You might have a 12 volt drain happening now. Something is taking volts from your battery just like you leaving your headlights on all the time when the car is parked.

take one of the battery cables off the battery and see if it sparks while removing it, if it does you have a shortage some where in the elect. system , this is the possible cause of the battery drain. If a shortage is present, you'll need to have wind or a fan blowing at the battery to keep gases from the battery blown away, as they are explosive,go to the fuse panel and remove one fuse, go to battery and touch the cable to the post, if it sparks, replace fuse and pull another one, once you pull a fuse and don't get sparks , then you located part of the problem, you have a shortage in this part of the system. At least this will let you know where the short is. Also, auto part stores sell a little switch which disconnects the battery,you can install one of these and flip the switch when not in use and prevent the power drainage.

all vehicles use a certain amount of power nowadays, its the keep alive memories of the computors , radio for channels and clock etc, although this drain is minimum it will drain the battery over a period of time, just like a cell phone even if you are not using it it stays alive , either get a trickle charger of disconnect the batt , hope this helps

Have a drain somewhere. Search google for "finding car battery drain"

sounds like its wired up wrong, remove the radio unplug the connector and remove the radio, then check all your fuses must have blown one when radio was installed, after that charge battery and with radio removed see if battery goes dead, if not recheck wiring to radio, common problem with vw aftermarket radio,they are installed wrong,good luck,