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12V battery issues (error messages/car charging problems)

StephRob

Member
Jan 26, 2012
209
3
Kentfield CA
We got our Model S exactly four weeks ago to the day. Today we got a warning signal that read "12V battery needs servicing" and below that "Replace 12V battery soon". Has anyone else gotten this warning? Can I drive the car with this warning on? I'm not sure what even runs on the 12V battery.

I called service but they couldn't help me until tomorrow morning.:frown: It sounded like they are going to want me to make the drive down to the Fremont or San Mateo service centers to get it replaced, which I'm none to happy about. That can be over an hour each way plus the time for the repair and that is a huge chunk of my day. I really hope they send a ranger, or I'm not going to be too happy.
 
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dsm363

Roadster + Sig Model S
May 17, 2009
18,279
160
Nevada
In the Roadster at least, that meant you couldn't unlock the doors without the physical key. The Model S has no physical key but does have that space on the windshield you hold the key to open the doors. I hope they can send a Ranger, they should do that if you ask since it's a warranty item.
 

MitchL

S#945
Dec 28, 2011
183
3
Saratoga, CA
I had this problem. It started the day I took my Model S home.

Here's how the problem was explained to me:

The Model S draws power from the 12V battery whenever it needs power to run the computers and other stuff and the main contactor (that controls electricity from the big battery) is off. For example, when the car is sleeping at night, in certain cases when the radio/accessories are on, etc.

This battery is supposed to be trickle-charged during the regular charge cycle, and the trickle charge rate is supposed to be greater than the drain rate.

-- but this is not always the case. My battery seemed to have an unusually low charge from the start (but there was a reason for this, I found out later).

The remedy that was suggested was:

- Go for a drive. Run down about 40mi of charge.
- Plug in for a recharge in range mode.
- Set charging amps to 5 (minimum).

This guarantees the trickle charger will run for a long time. They asked me to charge for 24 hours this way.

In my case, a service slot opened up the following day and they replaced my battery. Later they called and told me this procedure would not have worked for my particular battery because it had a bad cell.

BUT: Your battery might be fine, and this procedure might work.

Future firmware updates are supposed to address this problem more aggressively, either by reducing 12v power consumption or maybe increasing the charger current.

So: I don't really know if this would have worked, but it seems plausible.

Tesla service was fantastic replacing my battery, by the way. Super pleased.

/Mitch.
 

MitchL

S#945
Dec 28, 2011
183
3
Saratoga, CA
So if I charge at 80 amps everyday then I'm going to have more 12V issues than if I charge at 40 amps everyday?

I hope not, but your logic is along the lines of what I was thinking when I heard this. The understanding in my case was that my 12V battery was for whatever reason lower than it should have been.

The car is supposed to defend itself, and enable the main battery when it needs to. I think this is mostly a software issue assuming your 12V is good from the start. We'll see of course. I'm on week 2 with my new 12V battery and my usage pattern is to drive short distances and recharge every night (standard mode charge). So, the theory is that I should not be trickle charging my 12V very much because all my charge cycles are about 2 hours at the very most.

/Mitch.
 

mknox

Well-Known Member
Aug 7, 2012
10,103
1,894
Toronto, ON
Dare I ask... could you simply connect a standard automotive 12v battery charger to the 12v battery and charge it that way? Beats 24 hours of 5 amp charging in my mind.
 

FlasherZ

Sig Model S + Sig Model X + Model 3 Resv
Jun 21, 2012
7,028
1,025
Dare I ask... could you simply connect a standard automotive 12v battery charger to the 12v battery and charge it that way? Beats 24 hours of 5 amp charging in my mind.

From a DS: reportedly there are accessible terminals behind the nosecone which would permit this. I have not verified this nor do I vouch for its accuracy.
 

arg

Supporting Member
Supporting Member
Aug 22, 2012
1,815
1,816
Cambridge, UK
Dare I ask... could you simply connect a standard automotive 12v battery charger to the 12v battery and charge it that way? Beats 24 hours of 5 amp charging in my mind.

The owners' guide seems to suggest doing exactly that in the case where the car has been allowed to go flat - apparently, the anti-bricking system totally shuts down the main pack and so the 12V goes totally flat running the auxillaries, so you need to charge the 12V before you can wake it up enough to start normal charging.
 

StephRob

Member
Jan 26, 2012
209
3
Kentfield CA
The remedy that was suggested was:

- Go for a drive. Run down about 40mi of charge.
- Plug in for a recharge in range mode.
- Set charging amps to 5 (minimum).

This guarantees the trickle charger will run for a long time. They asked me to charge for 24 hours this way.

/Mitch.

This is exactly what Tesla service recommended that I do as well, so going through that process now. It kind of concerns me that this happened though with such a new car. Also, Wednesday through Sunday (two days before the problem started yesterday) of the Thanksgiving holiday, we were staying at a home with only a standard household 110v outlet to charge from. (That worked out fine for charging actually.) But it would seem to me that that would have been a lot of very recent "trickle" charging that would have charged that 12V battery. We'll see if this procedure tonight solves the problem.

This reinforces to me that we REALLY need a thorough, thoughtful, comprehensive owner's manual for this car that I just sprung (gulp) $120K for. The very perfunctory manual that is currently available doesn't even mention the 12V battery, except in a footnote in the instructions to prevent against bricking. For a non-technical person like myself (and like probably 99% of the people that Tesla is trying to sell this car to), that is just unacceptable. Per FlasherZ: "accessible terminals behind the nosecone"!!! What the heck? How am I supposed to know that? Or how to access them? Or what to do once I do? Or what the 12V battery even does? And what happens to the car when the 12V dies? And how does it relate to the 85kwh battery? I am a person who reads the instructions thoroughly every time I have to jump start an ICE car (which I do in my family because my husband wants nothing to do with it). I have great respect for all of you here on this forum with extensive knowledge of battery technology, software, ICE engines, electric motors and so on, but I have none of that and neither does the general public Tesla wants to sell to. While I'm sure (at least I hope) this episode is very minor, I feel like I'm in the dark, can't drive my new, very expensive car for a day and I don't really know what is going on with it. Sorry for the rant, but I hope if this problem hasn't resolved by tomorrow morning, Tesla will send someone up here immediately. (And I really hope this doesn't happen again, because I have no idea what I did or the car did to cause this problem in the first place. With a regular car, I know if I leave my lights on, the battery will go dead. No idea here. OK, really done with my rant now.)
 

Babylonfive

Power12
Feb 3, 2011
719
6
Cedar Park (Austin), Texas
From a DS: reportedly there are accessible terminals behind the nosecone which would permit this. I have not verified this nor do I vouch for its accuracy.

It might be a nice add-on to place a charging socket connected to the 12V battery, but accessible in the frunk, so that external charging or monitoring could be done.

I might do that myself if they don't offer it.
 

StephRob

Member
Jan 26, 2012
209
3
Kentfield CA
i think technical people are at least 50%.

On this board, maybe (actually probably), but I don't think that's the case for the luxury car-buying public at large. I come from the financial world, where there are lots of people with the financial resources to buy a Tesla, but I can't think of one that would say like BabylonFive just did that it would be great "to place a charging socket connected to the 12V battery, but accessible in the frunk, so that external charging or monitoring could be done. I might do that myself if they don't offer it." No one I deal with would know how to install a charging socket connected to the 12V battery in the frunk, or frankly want to deal with something like that.
 

StephRob

Member
Jan 26, 2012
209
3
Kentfield CA
To close the loop on this issue, the overnight trickle charge technique did not work. Tesla sent a Ranger out and he replaced the 12V battery. Still not clear why it went bad.
 

jerry33

(S85-3/2/13 traded in) X LR: F2611##-3/27/20
Supporting Member
Mar 8, 2012
20,002
24,694
Texas
To close the loop on this issue, the overnight trickle charge technique did not work. Tesla sent a Ranger out and he replaced the 12V battery. Still not clear why it went bad.

Batteries have infant deaths just like computer chips.
 

FlasherZ

Sig Model S + Sig Model X + Model 3 Resv
Jun 21, 2012
7,028
1,025
Yes, but either they got a bad batch (based on the number of failure reports we're seeing) or something about the electrical system is stressing them to failure.

My guess is that the change we saw in 1.17.29 was intended to address this -- perhaps it was trying to overcharge or something, and we ended up with the behavior I saw, which was that the car refused to charge at all without drawing a 12V load. That, in turn, appears fixed in 1.17.31.
 

tezco

Sig P85
Nov 9, 2012
819
4
Colorado
My Leaf has a current measuring clamp on one of the 12V battery leads, so I'm assuming the electronics keep track of current going in and out of the 12V.
 

steve841

Active Member
Jan 17, 2010
1,946
675
Ft. Lauderdale, FL
12v Battery Creates 5,000lb Paperweight.

Ok ... So my S is now 44 days old and today, once again as I was headed out to work, I was greeted with a completely dead Model S.

As it's the identical response I received the first time, I am sure the battery is dead.

But now I am wondering, how many others have experienced dead batteries?

The irony of a 12v battery being the Achilles heel of the Model S.

Im certain its a drain issue, not a 12v failure.

Nonetheless, Im still on 1.15.14. My driving routine is about as repetitive as can be (7am to work, lunch back to house, leave work at 4pm-maybe 30 miles total).

As it stands now, I am trying to stay patient, but on a day made for the Model S (55 degrees, no clouds) which we don't get enough of, I am so disappointed. Not to mention the wife's question, "Did your car die AGAIN??"


Here's my original post in the mechanical issues thread ...

Uh oh ... today's surprise:

Went to the garage to head to work ...

Step 1. Double click the remote. NOTHING. Hmmm... double clicked again. Nothing. Repeat in disbelief several times. NOTHING.

Step 2. OK ... run through common sense issues: push door handle. Nothing. Next door handle. NOTHING.

Step 3. OK ... next step, get other key... repeat step 1. NOTHING. Double click trunk ... click (it unlatched and that's it).

Step 4. TMC

Step 5. Give local service till 10am to get to work and call for reinforcements.
 
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stevezzzz

R;SigS;P85D;SigX;S90D;XP100D;3LR;YLR
Nov 13, 2009
6,100
122
Colorado
I feel for you, Steve841. There is nothing more disconcerting in a daily driver than for it to leave you stranded. Once is bad enough (early adopter notwithstanding), but twice will have you researching the lemon laws in your state. My Roadster went to a no-drive-power state once when I was on the road, and a failed 12V battery left it completely unresponsive in a parking lot on another occasion. But that was in 2-1/2 years, not 44 days. My S, thankfully, has had only minor issues in the first three months.

There is another thread started recently by an owner in CT with a disabled car, but I can't find it right now.
 

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