i have battery drain in my 2008 535i
in 24 hours battery goes down to 9.7-10v , today i was around the car for some time and heard some clicking relay noise in the trunk (i think car should be in the sleep mode) , that was abs relay (per google after entering part number from relay unit 61366901469) , i removed the relay .
can this be a problem of battery drain ? is it worth trying replace it ($14) ?

 

have you had the battery tested? it could just need to be replaced.

 

battery is replaced by previous owner , i did charged it untill full , no fault codes or any issues
...i am concerned why the relay was clicking?

 

autozone checks battery's for free... althought you say it was replaced by previous owner, if a battery ever got to the point where it drained low, it could kill the cells in even a brand new battery. unless it is a heavy duty battery where it can be drained and recharged without problems. worth a shot. sorry i dont know about the relay, hopefully more people chime in.

 

There is a relay in the trunk under the spare tire that controls the charging of the battery while the car is on. I have heard of some situations where this relay goes out, and creates all kinda of electrical havoc.

The good news -- the relay (I have to find the part number again) is like $15 at the BMW dealer, so troubleshooting this issues isn't that big of a deal if it turns out your battery is okay. If not -- the I'd start looking at the alternator.

 

I had to replace the alternator in mine. Though my error read "battery charging system fault".. or something like that. IMHO, if you've never heard the relay click, then all,of a sudden there's clicking and a problem as well, well, for 15 bucks it sounds worth a shot. As far as the battery goes, if you have a receipt saying it was changed it probably was, if not then maybe not. Next thing to consider is the battery make, if its a cheap brand, and has been drained too much to many times, then it may have lost its memory and wont be able to hold a full charge. If it's memory capacity has been reduced to 10.8 VDC, then it'll never hold any more charge than that, which means that if an abnormal load is put on it, like leaving your lights on by mistake for a little to long, then it'll show a fault sooner than a fresh battery would. You might want to make sure it has the appropriate amp. rating too. Might check to see if the cars aux power circut shuts off too. A cell phone charger with a light will tell you that. Plug it in and lock the car, after an hr come back to the car and without unlocking it peer inside, if the chargers light is still on then the aux power circut is still running, and draining the battery. Just a couple ideas, hope they help.