Normal Current Draw On Car Battery. A battery with a reserve capacity of 80 minutes has an allowable drain of 20mA. I measured my 2004 MY Jetta TDI drain from the battery to be about 0026 amp whether the car was locked or not.
For example 60 Amp-hr005A of current draw 1200 hours of supply current and 60 Amp-hr025A 240 hours of supply current. Note those would be readings with no draw at all cables disconnected. While the electronic equipment in your car should not draw any current when the car is parked there are exceptions such as the security system in your car.
That is why the car manufacturers provide bigger amps in the car battery than it needs to start.
After a little research the 25 - 35 milliamp figure mentioned above still looks like a good rule of thumb to me. Be aware that some electrical loads like radios and power amps can draw low current when you turn them off with the power switch. A normal amount of parasitic draw for older cars is a reading less than 50-milliamp. Altogether they draw a very small amount of current.
