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

[ravedave]

Update on mine: picked it up last Wednesday; they said they put in the new "red" 12v battery to replace the old "grey" 12v battery, and replaced the entire main battery since apparently the contacts (relays?) were not working correctly, which led to the 12v not getting charged. On Thursday drove up to Tahoe with a stop in Folsom to charge up (why is it on 50 and not the junction of 50/80??), no problems. Today drove all the way back to St. Helena without recharge, and still had almost 100 miles left. All seems well again. Still a little nervous, though they assured me all should be well. Should also say the service was exceptional throughout.

That voltmeter is looking like a nice accessory....

 

[Saxena]

We received our first software update notice yesterday after getting our car at the beginning of May. Unfortunately, when we tried to perform the update, we got the message "12 volt too low to perform update". The good news is that the Bellevue Service center got us right in today and quickly replaced the 12v with the new red version. All is well, and we plan to do the software update tonight.

 

[mep]

Well, there has not been an entry to this thread in more than 2 months. Does that mean the 12V battery problem has been fixed?
I got my car about three weeks ago. Today at work trying to drive home I got three error messages. That the car needs service, may not restart and has a low 12V battery. All was functioning, climate worked, lights worked, power lift gate worked but car would not come out of P. After 15 min with Tesla on the phone and Tesla about to send a service guy all over sudden I could put the car in reverse and it came to life. I kept getting a few more error messages but could drive it to the service center. I now have a loaner until they figure out what is going on. Does that mean I may have the same battery issue that everybody here has been talking about? They should know by now whats wrong right?

 

[celter]

According to a Tesla representative in Norway the 12V battery problems have been adressed in the latest FW 5.6. The 12V battery is now always charged from the main battery. Can anyone confirm this? Or prove it wrong?

 

[JRP3]

I'm not sure what that would mean. The 12V has always been charged from the main battery, through a DC/DC converter.

 

[montgom626]

I'm not sure what that would mean. The 12V has always been charged from the main battery, through a DC/DC converter.

Good question, I thought it was always charged by the main battery.

 

[celter]

Good question, I thought it was always charged by the main battery.

Then how could it be flat, when the main battery had enough charge?

 

[brianman]

The 12V battery is now always charged from the main battery.

There are two things I read from this (if true):
1. When plugged in, the 12V doesn't get a boost from wall juice. It gets it whenever the main pack decides to offer it some.
2. The main battery does a more aggressive/continuous charge of the 12V rather than going in spurts / event-driven.

 

[JRP3]

There are two things I read from this (if true):
1. When plugged in, the 12V doesn't get a boost from wall juice.

It never did.

It gets it whenever the main pack decides to offer it some.

The DC/DC converter is what regulates the charge going to the 12V.

2. The main battery does a more aggressive/continuous charge of the 12V rather than going in spurts / event-driven.

Charge demand is determined by the voltage of the 12V battery and the programmed response of the DC/DC converter. Basically I don't think the Tesla representative in Norway referenced above knows what they are talking about. It's possible that the latest version of software has fixed a control problem with the DC/DC converter.

 

[jerry33]

Good question, I thought it was always charged by the main battery.

The problem here, excluding the batch of bad 12V batteries early on, is the 12V charging algorithm. Charge too long or at too high a rate and you cook the battery. Charge too little and the battery slowly drains to zero. I suspect Tesla doesn't have this quite right yet. However, look at the Leaf and Prius forums, and you'll see a bunch of 12V battery complaints there too. Old fashioned cars don't have this problem because the starter motor warns the driver when the battery is getting weak, plus the battery is used for more than just powering up the car.

 

[stopcrazypp]

Old fashioned cars don't have this problem because the starter motor warns the driver when the battery is getting weak, plus the battery is used for more than just powering up the car.

Old fashioned cars also have much larger batteries that are more tolerant of various charging conditions and take longer to drain when left uncharged.

 

[NigelM]

Data point: never had a problem with my 12V but Rangers were here to fix my wing mirror and proactively swapped out out my grey 12V for a new deep cycle red one.

 

[jerry33]

Old fashioned cars also have much larger batteries that are more tolerant of various charging conditions and take longer to drain when left uncharged.

That's also true. An additional 10 kg of battery would go a long way to improving 12V battery life and owner satisfaction.

 

[Cal1]

It never did. The DC/DC converter is what regulates the charge going to the 12V.
Charge demand is determined by the voltage of the 12V battery and the programmed response of the DC/DC converter. Basically I don't think the Tesla representative in Norway referenced above knows what they are talking about. It's possible that the latest version of software has fixed a control problem with the DC/DC converter.

So the DC to DC converter is basically a step down device to change the 400v to 12v? Kind of like a step down transformer.

 

[JRP3]

Yes, it's just like any 12V battery charger that takes line voltage and drops it down to 12V, except it doesn't have to convert it from AC to DC since it's taking it from the DC pack voltage. In fact in my conversion I'm using a Mean Well 12V power supply that was made to run from AC line voltage but also works with DC input.

 

[Jenny]

New to forum. New model S. Two weeks in got a warning that V12 battery low, do not operate but went away shortly therafter. They serviced it for four days saying firmware issue. Three weeks later, just got the warning again but it went away 20 seconds later. Having buyers remorse as I dropped a lot of money for a new car that gives me warnings. Question for model S veterans. Should I be worried? Is this a safety issue? Did I just buy a lemon? Am I going to get these warnings every 3 weeks? Thank you!

 

[Benjamin Brooks]

Sounds like you should call and tell them you want a brand spanking new 12v battery put in (I've had 3 in a little over 2 years)

 

[apacheguy]

New to forum. New model S. Two weeks in got a warning that V12 battery low, do not operate but went away shortly therafter. They serviced it for four days saying firmware issue. Three weeks later, just got the warning again but it went away 20 seconds later. Having buyers remorse as I dropped a lot of money for a new car that gives me warnings. Question for model S veterans. Should I be worried? Is this a safety issue? Did I just buy a lemon? Am I going to get these warnings every 3 weeks? Thank you!

Only had it replaced once and that was proactive. I wouldn't worry too much. The 12V is backed by the HV pack so it is not like a conventional car. You don't have to worry about it going dead even if left for several months at a time. Having said that I would raise the issue with service again, but don't get overly concerned about it.

 

[Moonwick]

I figure I'll add on to this thread instead of creating my own. Add me (85D, delivered 3/31) to the list of people having 12V battery problems; last night the "service 12V battery soon" message popped up on my dash. I've put a logging multimeter onto the jumpstart terminals behind the nosecone, and it looks like the car's in a state now where it's keeping the DC-DC converter (and thus the pack battery) continuously engaged, presumably to avoid relying on the battery and resulting in a situation where the car would require a jumpstart. Probably not good for vampire drain, but I'll gladly take that over a dead S until I can get over to the SC.

ETA: After hovering just under 13.9v for about an hour it looks like the battery voltage is now sitting at 14.88v and has been for at least 20 minutes. Hopefully this is an anomaly caused by the "battery determined to be defective" mode and not a standard float voltage, otherwise I can certainly see why problems with the battery are as common as they are...

 

[actionspa]

I figure I'll add on to this thread instead of creating my own. Add me (85D, delivered 3/31) to the list of people having 12V battery problems; last night the "service 12V battery soon" message popped up on my dash. I've put a logging multimeter onto the jumpstart terminals behind the nosecone, and it looks like the car's in a state now where it's keeping the DC-DC converter (and thus the pack battery) continuously engaged, presumably to avoid relying on the battery and resulting in a situation where the car would require a jumpstart. Probably not good for vampire drain, but I'll gladly take that over a dead S until I can get over to the SC.

ETA: After hovering just under 13.9v for about an hour it looks like the battery voltage is now sitting at 14.88v and has been for at least 20 minutes. Hopefully this is an anomaly caused by the "battery determined to be defective" mode and not a standard float voltage, otherwise I can certainly see why problems with the battery are as common as they are...

Hey Moonwick, so what was the outcome with your battery issue?

Last Thursday evening 5.21.15 I was stranded (at work) with the "12v battery low", "unable to start car" messages.
As disappointing as this was on my P85D with just 3K miles, I was very impressed with the service from the San Diego service center. I had a flatbed load my car and a loaner delivered to me all in about an hour. The service center stayed open late to receive my car, and sent me a text confirming it had arrived. The next day the 12v and the 85KW batteries were replaced due to the faulty contactor issue. The service center was keeping me informed every step of the way and delivered my car back to me with all new batteries, washed and shiny in less than 24hrs! Thank you to Lee and everyone at the San Diego SC for getting my baby back to me so I could keep my appointment this morning to have the dash cams installed!