Unless the manufacturer specifies otherwise, 35 milliamps, (.035 amps), is the maximum current drain allowed for all of the computer memory circuits. At that rate Chrysler and most others guarantee a good battery will crank the engine after three weeks. Shadeydaz is right that most will last longer, but Cadillac allows up to 50 milliamps because they have even more unnecessary computers than on other car brands.
Every manufacturer provides a means of disconnecting non-essential circuits to allow the car to be driven by the trucking people who brought it to the dealership without creating the large drain that would kill the battery while the car is in storage waiting to be sold TO a dealership. There may be a bullet connector near the battery's positive cable or there could be a fuse to pull. On some cars that fuse is called the "I.O.D." Fuse for "ignition off draw". On some, the air bag fuses are the two to pull. The owner's manual should list what to do to stop the drain.
Disconnecting the negative battery cable will stop all current drain, but for the benefit of the sorry owners of other brands of cars who might be researching a problem with Volkswagens, BMWs, other imports, and General Motors vehicles, disconnecting the battery should be avoided at all cost. They have many models that have designed-in problems that require a tow to the dealership after simply disconnecting the battery or letting it run dead. Replacing your old battery with a new one will result in a very expensive repair bill to have multiple computers reprogrammed or unlocked.
Inmyheart28, Hyundai, along with Toyota and Chrysler, is by far the most customer-friendly manufacturer in the world when it comes to the computers on their cars, and unless something changed in the last couple of years, you should not have a problem even if your battery does run down enough that it won't start the engine, but if you want to be sure, put a battery charger on it and charge it at the lowest rate for half an hour before trying to start the engine.
Sunday, May 20th, 2012 AT 8:11 PM