VW POLO 6R 2009 Car Battery Draining

[rlplaya]

Hello,

I have a problem with my car battery draining overnight. I've replaced my car battery due to same problem ( car not being able to start when not driving for a couple of days ) with Exide Premium 53ah, and after several months , same thing happened again. I checked my car battery, and it was around 11.7 V. Then I charged my car battery fully , and it was 12.72V when I installed it back. The next day it went to 12.44 volts, I drove for around 20 minutes and the next day it showed 12.42V. The following day ( day after I rode ) it went to 12.30V. I've been to several car electricians, and they say everything is fine, that there isn't any parasitic draw. I find it very unlikely, there is no way a healthy battery will discharge so much overnight. I've seen several people complaining about the same thing, but I still haven't found the solution. The multimedia isn't stock, the previous owner installed something similar to this ( https://www.lloydmotorgroup.com/Vehicle ... TMuWNA.jpg ) , could that perhaps be the cause? Also, I have noticed that my car lighter isn't working at all, could that be the culprit? Unfortunately, I don't have a good multimeter to meassure AMP's. I was thinking about pulling the multimedia and the lighter fuse, and then check if the voltage will drop significally overnight, but I am not sure if that would even work? The pervious owner did not have the problem, because he was driving 60km's a day, and I only do short trips few times a week. This is my third car battery in a span of few years, and I really don't think the solution is to drive a car in circles, just so the battery won't drain after a few days. Alternator has been tested and it works fine, the battery also holds charge when not connected to the car.

Any solutions, tips would be appreciated. I am not an expert, but that car behaviour doesn't seem normal to me.

Thanks!

[Maarten]

Does your car has the factory alarm (DWA)?
Aftermarket radio?

[rlplaya]

My car doesn't have the alarm, but it does have the aftermarket radio. However, as I wrote this yesterday, I may have found the solution, and it may be the stupidest thing ever. Yesterday I went for a 10-15 min drive ( when the battery was at 12.30V ) , and then I read that somebody wrote something about USB that caused the same problem to their car. When my car was turned off, I unplugged the USB from my multimedia , and tried to connect my phone via the usb cable to see what will happen. The phone started charging immediately , so it would make sense that the car is powering the USB stick all the time, even when the car is off. I unplugged the USB device, and today I checked the voltage again, and it is at 12.41V.
I won't drive today, and tommorow I'll check the voltage. If it doesn't drop, then I know the culprit. Ironically, I think when I went to my car electrician, I unplugged my USB beforehand, so that would explain why there was no drain.

[Maarten]

Good that you found it