Electrical battery drain - 2007 Lexus LS 460 L Sedan

All about parasitic draw. Check for a light in the trunk or under the hood. Also the dome light is easy to miss in the daylight.

https://www.fixya.com/cars/r29903527-parasitic_draw_car_batteries

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an electrical short is an electrical drain in a circuit thats not supposed to be a constant drain on the battery, the alternator recharges the battery but an electrical short will interfere with charging process.

Some electrical testing should be done on the starter circuit , connection's , cable's etc..... Voltage drop testing , Looking at wiring diagram's to see what all is involved in the starter circuit for your vehicle. Drains your battery when ? Driving ,sitting over night ? Parastic draw on electrical system ? Do you know how to test automotive electrical circuit's ? If not your best bet mite be to take your vehicle to a qualified repair shop.
Starter Voltage Drop
How to voltage drop test starter motor circuit

test for a parasite drain
How to do Parasitic Battery Drain Test How to Find Parasitic Battery Drain How To Perform Parasitic Draw Test EricTheCarGuy

The problem is that an electrical component in the BMW that should be dormant when the vehicle is shut down is actively drawing power.
The only way to track it down is to have tests run to see which circuit is drawing excessive power because there are numerous components that might be the cause.

You can learn more here...........
Solving Automotive Electrical Problems

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Seen this "mystery drain" many times. Check spark at the battery to see how big the drain is. For this simple test, blow away any (explosive) battery charging fumes. Leave one terminal on and gently touch the other to its post in fairly dark surroundings. Then try it again with the wires taken off the alternator. Your spark is now probably much less. Usually bad diodes leaking electricity backwards through the alternator cause this drain. Replace the alternator or the diode pack inside it. Some mechanics recommend actually measuring the drain.... hahaha. OK whatever.

Hi my name is Tom and I can help you.

Most battery drains are shorts in the electrical system. Also, you might have a light(such as a dome light or trunk light that is not turning off.

Electrical problems are the personal hell of mechanics because one wire touching the cars ground and you have a drain which will drive you crazy. If you have the time you can check all the wiring on the car, if not take it to a shop. They will spend hours finding it and never can charge you what it is worth.

TomE

The negative terminal is the earth
The larger cable is for the engine earth so the starter will work, the smaller one is the body earth, The car needs both for the electrics to work, If you disconnect the small cable the electrics may earth back through somthing else like the throttle cable and this will not stop the battery drain

try checking ur alternator its what charges ur battery..Tip start ur car remove the pos cable from battery while car is on and if it turns off its ur alternator

your problem is faulty electrical, you have to trace your electrical wires for a shorted line or an electrical component is always on causing the draining of the battery.