Unexplained Intermittent Battery Drain

[Chris Foulds]

Wondering if you guys could help figure something out the garage can't.

My 2013 Galaxy Titanium X model 1.6 TDi with start/stop. It randomly has complete battery drain, this can be anywhere between 2 days and 3-4 months and is regardless of the amount of use.
Latest incident was this morning it was completely flat, yet did 80 miles yesterday and the start/stop was even kicking in indicating the battery was good.
I have had the battery tested, all good, replaced the battery last month - still happens.
I have had it sit in the garage for two days with a amp clamp, no real drain.
I have turned things on and off with a multimeter attached and not seeing any excessive.
It is totally weather independent can be hot/cold/wet/dry.

I am convinced it might be something getting 'stuck on' occasionally after turning it off and locking up like a relay or something but have no idea where to start.

Any pointers appreciated.

[Mirez]

I would agree that sounds like the most likely scenario and isn't that uncommon actually on modern cars, especially if you've had any recall work done.

The reason I say that is that often during a recall, to save time they update firmware on certain controllers only instead of doing all of them and that then leads to software incompatibility with the older ones.

A working network should be going into deep sleep after 20 to 30 minutes so I would be looking at setting up the clamp again and then lock the car. If its under 100ma after that time then unlock and relock - try again.

My monies on a firmware issue though