Thanks Phil,
I didn’t know about the first responder loop, to do that also as well as disconnect the battery. I’ll load test the battery tomorrow, don’t trust the software update. Have a renewable energy day, Mark Mark E. Hanson 184 Vista Lane Fincastle, VA 24090 540-473-1248 phone & FAX, 540-816-0812 cell REEVA: community service RE & EV project club Website: www.REEVAdiy.org (See Project Gallery) UL Certified PV Installer My RE&EV Circuits: www.EVDL.org/lib/mh REEVA Demo: http://youtu.be/4kqWn2H-rA0 Fincastle Solar Weather Station <https://www.weatherlink.com/embeddablePage/show/a88920376f864ecabaed843dd8975b8d/signature> From: (-Phil-) [mailto:[email protected]] Sent: Sunday, November 30, 2025 8:13 PM To: Cor van de Water Cc: Electric Vehicle Discussion List; Mark Hanson Subject: Re: [EVDL] Cryptic Tesla Error Messages after “Update” The sleep on Model 3/Y is quite good as long as you aren't running sentry mode. It may lose 1% every 10 days or so (my 2018 Model 3). I can go several months without driving it or charging it and not worry. The Sleep on 2021+ cars is even better in most cases. The older cars such as pre 2021 S/X did not have very good sleep. Yes, you need to fire up all Teslas at least once a month if they are disconnected to renew the SSL certificates. For whatever stupid reason, Tesla only generates them for 2 year validity. I don't know any good way to check the dates without root. On Sun, Nov 30, 2025 at 4:55 PM Cor van de Water <[email protected]> wrote: If you are concerned about the Tesla discharging your pack while parked longer time, I can recommend disconnecting the 12v battery and making sure the main pack contactors have disconnected (Power Off). Dis will let your Tesla keep its charge for months if necessary. Only drawbacks are that you need to make sure you know how to jump start and if you leave the Tesla for more than 2 months without ability to contact the Tesla Servers, it might fail to fetch a new certificate and the Tesla engineers have chosen to make it impossible to renew if it was not done in the 2 months. Ask me how I know. The easiest way to (dis)connect 12v is the use of a remote relay that only takes a few milliAmps for a receiver that allows you to turn the 12v on/off with a remote, I have this in my 2013 S because it never sleeps and can suck down its entire 85kWh pack in 2-3wks. I had to do this when the charger failed and I had no time to fix it, 4 or 5 months later it still had the same charge, only could no longer connect to Tesla server... Cor. On Sun, Nov 30, 2025, 4:03 PM (-Phil-) via EV <[email protected]> wrote: 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/ -------------- next part -------------- An HTML attachment was scrubbed... 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