Battery drain - what is causing it?

[Dschubba]

Correction vin was 21170 approx with an R for 2024

 

[onuraiu]

Update to my "case", today is 25th of July and dealer measured (my Victron totally disconnected):

So 5 days ago those numbers were:
main: 12.5V
aux: 12.84V

Now those are:
main: 12.8V
aux: 12.39V

meaning, main battery went low and was charged from aux.
main: 12.5V +0.3V -> 12.8V
aux: 12.84V -0.45V -> 12.39V

To sum up, according to dealer that is all OK and nothing is wrong.

 

[onuraiu]

So after I got my car back, I planned to do a longer idle test at home, but unfortunately my neighbour got stuck in forrest with his range rover and needed help from my Track-Thor .
Anyway 29th of July at 8.40am I had disconnected my victron and aux battery (took off the cables from battery) - so there wasn't any my own things connected to the car and also charging from aux battery was disabled, as aux battery was not connected anymore.. Although I didn't know how to disable c.tech device..
I measured voltages:
main battery 12,68V
aux battery 12,94V
I locked the car from remote.

On the 1st of August at 3.45pm (3 days 7h 5min later), I opened the car from remote and measured voltages again:
main battery 12,27V (0.41V drop)
aux battery 12,85 (0.09V drop)

So during that 3d and 7h, main battery lost 0.41V... my calculation tell me that, if I go to airport and leave my car there approx 3 weeks and return, then most probably I won't be driving home without help from booster...

Next I'll swap batteries when longer idle period comes again.

 

[Dschubba]

So after I got my car back, I planned to do a longer idle test at home, but unfortunately my neighbour got stuck in forrest with his range rover and needed help from my Track-Thor .
Anyway 29th of July at 8.40am I had disconnected my victron and aux battery (took off the cables from battery) - so there wasn't any my own things connected to the car and also charging from aux battery was disabled, as aux battery was not connected anymore.. Although I didn't know how to disable c.tech device..
I measured voltages:
main battery 12,68V
aux battery 12,94V
I locked the car from remote.

On the 1st of August at 3.45pm (3 days 7h 5min later), I opened the car from remote and measured voltages again:
main battery 12,27V (0.41V drop)
aux battery 12,85 (0.09V drop)

So during that 3d and 7h, main battery lost 0.41V... my calculation tell me that, if I go to airport and leave my car there approx 3 weeks and return, then most probably I won't be driving home without help from booster...

Next I'll swap batteries when longer idle period comes again.

The aux battery does a good job of starting the car if the main one goes flat

 

[onuraiu]

The aux battery does a good job of starting the car if the main one goes flat

Yes, it does. And it also charges main battery when it's voltages go low, meaning after a while they both might be empty if there is a problem...

 

[Logsplitter]

Yes, it does. And it also charges main battery when it's voltages go low, meaning after a while they both might be empty if there is a problem...

No I do t think that’s quite correct. I’m sure the smartpass works by stopping the pulse charging of the main battery from the second battery at a certain percentage level so there is always enough to start the vehicle. Thats as long as you haven't added any additional loads to the second battery and drained that to. I’m I guessing it cuts off at around 50%. Check the smart pass manual and I’m sure it will be in there.