"12V Battery Need Service" error and aftermarket sound system

[ORB]

Hi all,
I'm working on an ongoing "12V battery requires service" problem in connection with an aftermarket sound system installation in my 2012 Model S. It may be caused by an improper sound system DC power connection, and I'm trying to determine the correct 12V battery terminal to use (see photo below).

After 6+ years of trouble-free operation following the installation of this sound system in 2013, this message appeared after I had the 12V battery replaced earlier this year. According to the Tesla service technician, if the DC power wire from a non-Tesla device is connected to the wrong terminal, the 12V charging system can be misled into throwing a 12V battery error due to the load current (as measured by a current sensor near the battery terminal) not correctly reflecting the changes in battery storage capacity that the charging system expects to see. The aftermarket sound system still functions normally.

The Tesla technician removed and isolated the aftermarket sound system wire, but declined to state what the correct connection point should be, because Tesla cannot officially sanction aftermarket device hookup to the battery.
The sound system installer has used the connection point shown in the photo (per instructions from Tesla) for a great many Model S installations, and has been extremely helpful while working with me to try to resolve this issue.

Due to the "12V battery requires service" message persisting even after the sound system installer reconnected the wire to what he believes is the correct connection point, I found it necessary to disconnect it again for the time being so that myself and Tesla can rule out any other 12V charging system malfunction.

So here is my question for you knowledgeable Tesla folks and/or sound system installers (@wk057, @FlasherZ et. al.): Could you please advise me as to what exact 12V battery terminal should be used for aftermarket sound system installation connections?

Thank you very much!
Oliver Barrett
Sunnyvale, CA

 

[eXntrc]

This most likely will not apply to you, but we've been seeing similar issues with aftermarket systems in the Model 3. It turned out to be due to inrush current with the Penthouse turning of during sleep, which probably isn't even a thing on the Model S. So this probably doesn't apply to you, but I thought I'd at least share the similar trouble codes and how it was eventually solved.

Travis documented it quite well in his series on his custom sound system.

You can read about the problem in part 5:

Tesla Model 3 Stereo - Part 5: Electronics

And you can read the solution under "Power Systems" in part 9:

Tesla Model 3 Stereo - Part 9: Summary and Lessons Learned

Again, this probably won't answer your question but maybe it might help point you in the right direction.

 

[ewoodrick]

I don't think that there is a proper point. The only points that seem to be sanctioned are the USB and 12V receptacle.
Because the car watches the 12V battery closely, if there's too much draw, that's when the battery service appears.

 

[Tam]

...correct connection point should be...

I thought this problem only happens to Model 3. I guess it's been so successful in weeding out after market add-ons in Model 3 so now Tesla is implementing to Model S too.

Model 3 has 12V consumption monitor. The correct way is any point after that monitor system so it can account your add-on consumptions.

If you bypass the system by connecting yours to the battery post, the monitor system does not count your add-on consumptions and let your 12V battery die.

You can safely tap any in power source in the cabin such as @ewoodrick said USB, cigarette outlet, and also any light cables, OBDII... because all of these consumptions whether little or a lot are counted by the monitor system and won't let your 12V battery die.

 

[bigdave79]

My aftermarket amp is connected in the exact same spot. I bought the car used in March and had the amp/sub installed shortly after. A couple of weeks ago I also got the 12v battery warning. Mobile tech replaced the battery but said if it happens again Tesla may not replace under warranty because of the sub and amp. My 12v was never changed since the car was built (late 2014) so it may just have been due for replacement. Guess I'll have to keep an eye on it.

 

[ORB]

Thanks for all your responses. My 12V battery error message came back, even with my sound system disconnected. I’ve got a service appt. this week to investigate, the 12V battery was in good shape originally but as Tam mentioned, it may possibly not have been not properly charged over the last several months and thus deteriorated. My plan going forward is to run the sound system from a separate “house” battery for the time being, which I’ll need to manually keep charged from time to time.

Oliver Barrett

 

[mckemie]

I come here from the V2H supplement thread:
Powerwall 2.0 Backup Runtime Extender
I find the information linked to here HIGHLY useful. Thanks!

It would also be useful to know if/when S/Xs adopted the scheme of restricting DC-DC power to the 12v battery. Anyone know? Recall how troublesome 12v lead batteries are in early Ss. My experience is that the life of a lead battery was around one year.