I think Tesla can ship you a battery, but I don't know what the charges are, but it's probably less than $50.
The likely reason it shows up after an update, is it has to stop the 12v support (DC-DC converter) during the update for some time, so this will attempt to discharge the 12v battery somewhat, and can get it low enough to trip the alert. I'm not exactly sure what the phantom draw will be at the airport in this state, but it could be as high as 8% per day. It depends on many factors. I recommend you perform the reset of the system now, and see if it comes back, you might be OK for a week. It will take 5 minutes and all you need is a 10mm wrench or socket to disconnect the negative lead on the 12v battery, then unplug the fireman connector, wait for a few seconds, then reconnect it, and then reconnect the 12v battery. Here is how to do those things: https://service.tesla.com/docs/Public/diy/modely/en_us/GUID-AE762FFF-8268-4BDF-9246-A2BB8D17B0B4.html On Sun, Nov 30, 2025 at 3:48 PM Mark Hanson <[email protected]> wrote: > Thanks Phil for your help and the thoughtful reply. > Seems odd to me that it does an update, then this bad 12v battery message > shows up. > I’m 3 hours from Richmond (Tesla) , saw one to replace my new battery > (replaced from Advance Auto $350) with another new battery from EBay > 1129182-00-b as you noted for $235. > I have a load battery tester so I’ll check it tomorrow but I suspect the > new update screwed up something. I also have my “old” 5 year battery that > load tested good I can put back in. > So what happens if I ignore it and it runs the dc converter while I’m > parked for a week at an airport (like I have to do next week)? > Best regards > Mark in Roanoke Va > Sent from my iPhone > > On Nov 30, 2025, at 5:07 PM, (-Phil-) <[email protected]> wrote: > > > Did you replace the 12v with one from Tesla or some 3rd party brand? > Many 12v batteries now are made with garbage lead that isn't refined well, > so ends up with a short life. Do you have any accessories hooked to the > 12v system? If you tap the 12v battery for anything this can be the > result. If you use the OEM Atlas battery it shouldl last from 3-5 years > depending on climate and your drive cycle. > > VCFRONT measures the amp-hour capacity of the 12v battery and will set > that alert when it detects capacity is insufficient to allow sleep, and it > will then disable sleep so you don't end up with a dead car. If you want > to double-verify this, you can reset the amp-hour counter by disconnecting > the 12v battery, then the HV, then reconnect both. The alert will go away, > It will then re-measure the capacity and the alert will return if it's > still too low. > > FYI: The high-quality 12v battery made by Atlas is only $100 at any Tesla > service center. (Down in cost!) Part # 1129182-00-B. You can walk in and > grab one off-the shelf. > > Here's my video on the 12v system that explains more: > https://www.youtube.com/watch?v=i27lApNWkyA > > On Sun, Nov 30, 2025 at 12:29 PM Mark Hanson via EV <[email protected]> > wrote: > >> Hi Folks >> The Tesla Y 2021 did another (almost daily unnecessary) update and now >> displays a “VCfront a402 Electrical system backup power is unavailable. >> Vehicle will consume more energy while idle. Software will not update”. >> Then expanding to: “VCfront a192 electrical system is unable to support >> all features. VCfront a182 schedule service to replace low voltage battery. >> Software will not update”. >> >> But then displayed updated software minor fixes. The pricy 12V battery >> (due to the non standard size), I replaced 6 months ago. >> Do I just ignore this silliness? Is there a way to reset these screen >> messages? >> Go back to a previous “update”? >> Best regards Mark in Roanoke Va >> Sent from my iPhone >> _______________________________________________ >> Address messages to [email protected] >> No other addresses in TO and CC fields >> HELP: http://www.evdl.org/help/ >> >> -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20251130/23967fc8/attachment.htm> _______________________________________________ Address messages to [email protected] No other addresses in TO and CC fields HELP: http://www.evdl.org/help/
