RomRaider

09 WRX AU, recently had a flat battery several times, after a couple of days not driving.
I know your forum does come up on google so thought as a credible community this is the place.
Initial investigation I could find no faults in the many lights and switches.
Noted literally thousands of reports on various forums, many users and dealers changed batteries, some as many as three times in a month, no faults found with cars or batteries, lots of bad mouthing of Subaru.
Some solved the problem with BIG batteries, they take longer to drain:)
I found it hard to believe no one had a solution, a real answer. The gurus, the dealers, Subaru.
More investigation, the car was was losing about 1200ma continuously, general feeling is 70ma is normal for a sleeping Subaru. Used the main fuse box to try and isolate, found the fuse labeled BACK UP killed the drain.
A laugh, in the user manual it is labeled BACK UP LIGHT, that is WRONG. It does many things and is part of the power for the BIU Body Integrated Unit, you gurus will know it controls many things, everything body/key related.
Pull the fuse and the car will run but all body related function are screwed. AC can work, a bit hot here.
If you are trying to trace this sort of thing leave the keys in the house OK.
Over a couple of days trying many haphazard checks, removed that fuse a few times.
Drain stayed the same about 1200ma.
The words BACK UP are relevant, the BIU is a computer, I think it does save all the info about settings, audio, nav, maybe some switches, someone will know exactly.
I set up to start checking the inside fuses, extended ammeter leads so I could see the gauge in the car.
On one occasion when the ignition was off and I connected the battery the CD player re-initialized itself. wtf.
(the Audio unit was OFF)
Drain gone!!!! I think the CD player was in some weird mode, not properly off maybe.
This car takes about 3 minutes to go to sleep when you lock it, I believe in that 3 minutes the BIU is doing its stuf.
When sleeping it pulls 50ma.
My battery is 5 years old!!
What about those 1000s of other battery drain, battery failure reports?
I bounced this cause off a good tuner/mechanic, he said he had seen it on a GM sedan once.
This topic is a bit long, sorry but 1000s of people need to read it, imo.

Thanks for your feedback,

My new battery is like 3 weeks old, and i wasn't able to start this morning.
I didn't have time to test but, i think i have the same problem. ( 6CD charger ? )

BTW : My VARTA battery has a smaller pin than the subaru connectors. I'll try to have a refund.

Yes, mine was a 6 cd changer.

Thanks,

For no reason, it seems to be working again...

My air mixing actuator is broken, so i unplugged it, but i recently thought about how it could drain the battery, by staying powered while trying hard to get the actuator to get in position.

We'll see !

For info, I think I mentioned, my CD changer suddenly reinitialised and drain stopped.
I believe it was hung up in some way, causing the drain. For a month or so!
Possibly caused by switching off the ignition while the CD changer was doing something.
Hence my advice, if you have a mystery drain, try operating everything that might interact with the BIU computer.

Good Luck.