Auxiliary Battery Charging - an Observation

[Tim94549]

A couple months ago I experienced the Dead 12v Battery issue; unexplainably. I read a lot about how the Battery Saver works - requiring a minimal 40% SOC of the traction battery - it then periodically tops off the 12v Aux Battery. (I had previously allowed by traction battery to get down to around 20% before charging).

So at various times overnight, I get the Bluelink alerts about my doors being unlocked - which they are since it's securely parked in our garage. I get these alerts around 4 times per night (or day - when parked for a long time). The alert times seem to be every 4 hours. My thought/belief is that THESE are the times that the Aux Battery is getting topped. And if true, I believe that if I allow the SOC to get below some threshold (40% ? 35% ? 30% ?) that I will no longer receive those alerts and thus the Aux charging will no longer function.

Thoughts about this ? Am I on to something ? MY 2020 Ultimate

 

[KiwiME]

If you had a BMS update in the last 2 years you might find that number is now 50%. But it always charges the 12V battery once a day anyway.

I think installing a BM2 on the 12V battery might offer useful information.

 

[Tim94549]

I haven't had any BMS update for several years. But 50% ? that's crazy that we're required to maintain a SOC of 50% just to keep the AUX battery from going dead. This whole AUX battery thing isn't designed very well, imho .. I mean, what happens if we're on a long trip and the traction battery gets down to 15-20% ... this all implies to me that there is no AUX charging at all until we get the Traction Battery topped up.

I have a battery tester that I just leave plugged into the 12v thing in the console. So I keep an eye on it that way. And so far (since my battery drained a couple months ago) it's maintaining 11.8 - 12.4v .. I was just thinking that what I was seeing via Bluelink (doors open) was that the car was waking up to top the AUX battery and found the doors unlocked at the same time .... It's pretty consistent - every 4 hours.