HELP - Best way to track down source of battery drain?

[STAATS]

Despite the extensive work I have done on my car and the 3xFSAE cars I have built in my time I am generally electrically illiterate. As part of my rebuild I went to a CSL battery and had replaced my Alternator... early on I found the rebuilt alternator I used was rubbish and I couldn't drive the car for long or afford to have it not on trickle charge... Since replacing the alternator with a brand new Valeo I have had no issues in that respect but I still have battery drain issues... if the battery is connected it will drain in ~1-2weeks... prior to my rebuild (admittedly with an OE M3 battery not CSL) I was able to leave my car for 7wks during and overseas trip without a charger and start it straight up when I got home... if I disconnect the battery (I have an isolation switch) I can leave it for over a week and reconnect it and it is still 100%... so obviously I have a battery drain issue.

I have a few candidates:

• CYHY Hidden Dash cam
• RaceCapture Track
• Avant-3
• BT OBD-II adaptor
• Radium Automotive Fuel Surge Tank Kit
• Battery Isolation switch
• CTEK Charging Panel

But in general I wanted to know the best logical way to go about diagnosing a battery drain issue and how to close-in on the exact device or circuit that is causing it?

Can I measure something on the battery using my multimeter and then pull fuses from circuit one-by-one and be able to pickup which one is causing the drain? The way most of my things are wired in is hardwired and hidden so I don't want to remove panels until I confirm which one it is... but obviously if that is the best way to do it then I will...

So if anyone can provide some guidance on a nice logical way to try track it down that would be most appreciated. Understand that for most this may be a very dumb question so I am fully expecting and probably deserve some sarcastic responses haha. As long as one of them is some good helpful guidance then that would be great.

[eacmen]

My bet is anything plugged into OBD adapter port since there is a constant 12v and switched 12v going to that port. Its been my experience that most devices use the constant 12v source versus switched.


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[STAATS]

My bet is anything plugged into OBD adapter port since there is a constant 12v and switched 12v going to that port. Its been my experience that most devices use the constant 12v source versus switched.

The CYHY Dash Cam is hooked to my radio power and has a constant and switched 12v power as well. It could be OBD-II port but I am pretty sure I have pulled that adapter and tested before but I can always do it again... but again I want to know a way I can diagnose live... vs just pulling something out and waiting a few days to see the results.

[eacmen]

The CYHY Dash Cam is hooked to my radio power and has a constant and switched 12v power as well. It could be OBD-II port but I am pretty sure I have pulled that adapter and tested before but I can always do it again... but again I want to know a way I can diagnose live... vs just pulling something out and waiting a few days to see the results.

Put a current meter inline to measure draw.


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[Rosie]

This is the simplest way to test for current draw:-

https://m.youtube.com/watch?v=8c43Ix6Lf2c

They missed a step though.
After you roll the door catches you should lock the car. An E46 goes to sleep within 5mins after you lock it (if there’s nothing keeping it awake).

[heinzboehmer]

After you roll the door catches you should lock the car. An E46 goes to sleep within 5mins after you lock it (if there’s nothing keeping it awake).

Unless you have an alarm installed. The ultrasonic sensor will pick up movement and set off the alarm (ask me how I know).

[Rosie]

Unless you have an alarm installed. The ultrasonic sensor will pick up movement and set off the alarm (ask me how I know).

True, but if you press the lock button on the key twice when you lock it, it will turn off the interior sensor.

[heinzboehmer]

True, but if you press the lock button on the key twice when you lock it, it will turn off the interior sensor.

Oh cool, did not know that.