12v battery issue explanation, sort of...

[Aussie Bob]

I just had my 12 v warning come on which is really disappointing as I have only had the car for 4 months. My problem is exacerbated by fact we travel a lot and the car was not driven for long periods. It has also been very cold in Ottawa. I presume using the Tesla App to check our car while away may not have helped the situation. I travelled the same amount when I owned my previous ICE cars and rarely had such a major problem. If it battery was dead with my ICE, it was an easy fix with calls to CAA.

I have followed instructions re: charging car at 50% level at low amperage while away but I was not given any instructions as to what to do to the 12v battery while away. Historically I used trickle chargers for my old ICE cars which enabled 12v battery to work on my return in most cases. This was a very simple operation to perform before going away.

However applying a trickle charge to the 12v battery of the Tesla Model S is not nearly as easy but reading this site has provided me with iinstructions as to what I can do to do to apply a trickle charge to the 12v battery while we are away. I will also be able to check with the ranger, who is coming on Friday to replace the battery, how to do it. A major drawback in not having a service station, where I live in Ottawa, is the need to wait for a service repairman to come to you in emergencies. In our case a wait of 4 days versus hours for an ICE car!

As reported many times in this site, I have no idea how much power is left in the battery unlike my Apple products. This makes me very reluctant to use the car until the battery is replaced. This is Not ideal as the Model S is my main mode of transportation. It makes attending several important appointments during this wait, without my own transportation, a major problem.

 

[AmpedRealtor]

I just had my 12 v warning come on which is really disappointing as I have only had the car for 4 months. My problem is exacerbated by fact we travel a lot and the car was not driven for long periods. It has also been very cold in Ottawa. I presume using the Tesla App to check our car while away may not have helped the situation. I travelled the same amount when I owned my previous ICE cars and rarely had such a major problem. If it battery was dead with my ICE, it was an easy fix with calls to CAA.

I have followed instructions re: charging car at 50% level at low amperage while away but I was not given any instructions as to what to do to the 12v battery while away. Historically I used trickle chargers for my old ICE cars which enabled 12v battery to work on my return in most cases. This was a very simple operation to perform before going away.

However applying a trickle charge to the 12v battery of the Tesla Model S is not nearly as easy but reading this site has provided me with iinstructions as to what I can do to do to apply a trickle charge to the 12v battery while we are away. I will also be able to check with the ranger, who is coming on Friday to replace the battery, how to do it. A major drawback in not having a service station, where I live in Ottawa, is the need to wait for a service repairman to come to you in emergencies. In our case a wait of 4 days versus hours for an ICE car!

As reported many times in this site, I have no idea how much power is left in the battery unlike my Apple products. This makes me very reluctant to use the car until the battery is replaced. This is Not ideal as the Model S is my main mode of transportation. It makes attending several important appointments during this wait, without my own transportation, a major problem.

Go ahead and drive your car until the battery is replaced. This is a proactive warning that should give you plenty of lead time. Another member here was scheduled a month out for his 12v and the service center said it was fine to drive in the meantime. You shouldn't have anything to worry about. My service center also told me the same thing, that the 12v warning is an early warning and that it's safe to drive until it's replaced. Schedule the replacement with service and drive the car in the meantime.

 

[Aussie Bob]

Go ahead and drive your car until the battery is replaced. This is a proactive warning that should give you plenty of lead time. Another member here was scheduled a month out for his 12v and the service center said it was fine to drive in the meantime. You shouldn't have anything to worry about. My service center also told me the same thing, that the 12v warning is an early warning and that it's safe to drive until it's replaced. Schedule the replacement with service and drive the car in the meantime.

Thanks for advice. However in Ottawa it is extremely cold here at the present time with temperatures expected to reach minus 24 this weekend. Today was warmest day in weeks at minus 7 C. My Tesla service rep mentioned that I should be able to drive the car provide I drive slowly; avoided using battery devices (ie Radio etc) and make certain I plug the car in whenever the car is not in operation. As a result I am reluctant to chance driving the car as it is not possible to plug in the car where I have my appointments. Also if car does breakdown in middle of winter, it would not be an ideal situation. If the weather as warmer I would chance it as you suggest.

 

[Cottonwood]

Thanks for advice. However in Ottawa it is extremely cold here at the present time with temperatures expected to reach minus 24 this weekend. Today was warmest day in weeks at minus 7 C. My Tesla service rep mentioned that I should be able to drive the car provide I drive slowly; avoided using battery devices (ie Radio etc) and make certain I plug the car in whenever the car is not in operation. As a result I am reluctant to chance driving the car as it is not possible to plug in the car where I have my appointments. Also if car does breakdown in middle of winter, it would not be an ideal situation. If the weather as warmer I would chance it as you suggest.

I am afraid that your service rep is very confused. When the Tesla is on, the 12V devices are driven by the DC to DC converter. Driving slower only reduces the draw on the main traction battery, not the 12V battery. The 12V battery is more stressed by being cycled when the car is off than when it is on and the DC to DC converter is driving the 12V bus.

 

[PlanB]

I find it interesting the different opinions from each service center. When my 12v light came on last week I called Tesla immediately and was told that it was a warning light and that it was ok to drive but that I needed to bring it in asap.

 

[Mayhemm]

However applying a trickle charge to the 12v battery of the Tesla Model S is not nearly as easy but reading this site has provided me with iinstructions as to what I can do to do to apply a trickle charge to the 12v battery while we are away. I will also be able to check with the ranger, who is coming on Friday to replace the battery, how to do it. A major drawback in not having a service station, where I live in Ottawa, is the need to wait for a service repairman to come to you in emergencies. In our case a wait of 4 days versus hours for an ICE car!

Yeah, it always sucks to have car problems when you really need to use it. I had a similar situation last autumn when one of the car's charging units went. I was on a roadtrip at the time and over 4000km from home. In my case the Ranger only took 2 days to arrive and repair the car but but I was still very pleased with this. If I had a regular car, I likely would have spent those 2 days just waiting on a service appointment which would only diagnose the problem (probably unsuccessfully) and then have to come back again at a later date for them to actually fix the car. It's not too likely that process could take less than 2 days. Most service centers are backlogged for weeks, if not months.

Sorry to hear you're unhappy with your service experience.

 

[Aussie Bob]

I was not told by Tesla rep that I could not drive the car but it was stressed that I should plug the car in whenever it was not being driven. As a new owner with our cold weather and lack of chargers where I had to park the car ( when not at home) made me decide to not use the car until ranger arrives and fixes problem. I am pleased that service rep can travel from Montreal to Ottawa to fix my problem but I wish it could be done quicker. We need an Ottawa service centre.

Another point: does anyone have suggestion as to how to look after 12 v battery of Model S when you leave car sitting for long periods - 2-3 months? I have already received advice from Tesla that I should charge to 50% level at low amperage when I leave the car sitting. Is this enough for the 12v battery?

 

[AmpedRealtor]

I was not told by Tesla rep that I could not drive the car but it was stressed that I should plug the car in whenever it was not being driven. As a new owner with our cold weather and lack of chargers where I had to park the car ( when not at home) made me decide to not use the car until ranger arrives and fixes problem. I am pleased that service rep can travel from Montreal to Ottawa to fix my problem but I wish it could be done quicker. We need an Ottawa service centre.

Another point: does anyone have suggestion as to how to look after 12 v battery of Model S when you leave car sitting for long periods - 2-3 months? I have already received advice from Tesla that I should charge to 50% level at low amperage when I leave the car sitting. Is this enough for the 12v battery?

The charge level of your high voltage traction battery has no impact on the 12v unless your traction battery is dead, in which case it will not be able to recharge the 12v when needed. That means you'd have to run your traction battery to zero and leave it unplugged in order for there to be any risk that the 12v won't charge. As far as doing what is best for the high voltage traction battery during an extended absence, I would suggest setting it to 50% and make sure your sleep mode is ON. Set it and forget it.

 

[Aussie Bob]

I was not told by Tesla rep that I could not drive the car but it was stressed that I should plug the car in whenever it was not being driven. As a new owner with our cold weather and lack of chargers where I had to park the car ( when not at home) made me decide to not use the car until ranger arrives and fixes problem. I am pleased that service rep can travel from Montreal to Ottawa to fix my problem but I wish it could be done quicker. We need an Ottawa service centre.

Another point: does anyone have suggestion as to how to look after 12 v battery of Model S when you leave car sitting for long periods - 2-3 months? I have already received advice from Tesla that I should charge to 50% level at low amperage when I leave the car sitting. Is this enough for the 12v battery?

The service ranger replaced my 12v battery yesterday in very cold temp which at one point in day reached minus 26C (-35c with wind chill). Service was fantastic as he not only changed the battery; corrected tire pressure and started download for 6.1 software plus overall checked the car. I was impressed as work was done in an unheated garage. We supplied regularly hot packs to warm his hands.

I also found out a little more about the 12v battery when the warning light comes on. The ranger advised that the car would continue driving once the car is going when you see the notice but I should arrange to have the battery replaced ASAP. He did add however that when the car is not in use that it should be plugged in. Hence he mentioned that I made a wise choice to not use the Model S for my appointments of 2-3 hours duration as the locations to where I was going did not have charging stations.

As for my long trips he mentioned all I had to do was charge to 50% level at 40 amp level.

Conclusion for weak 12v battery: Car can be driven as long as it is plugged in when not in use and change battery ASAP.

 

[AmpedRealtor]

As for my long trips he mentioned all I had to do was charge to 50% level at 40 amp level.

While I'm not Tesla, I can tell you that there is nothing unique about the 40A charge level. Do you have an 80A HPWC? If so, running at 40A will run one of your two on-board chargers at maximum utilization. If you charge at 80A then both chargers are running on full. During an extended absence, it is probably not a good idea to run one or both chargers at their maximum capacity because you want to insure against a failure when you are gone. If you increase your charge rate to something above 40A, the current is split between the two chargers. So at 60A, each charger gets 30A. That is preferable to running a single charger at 40A.

 

[Aussie Bob]

While I'm not Tesla, I can tell you that there is nothing unique about the 40A charge level..

I only have a 40 Amp service which many times only puts put 30 Amps. I could not increase my panel to accommodate an 80 Amp service. The ranger knew my limitations and responded accordingly.

 

[Andyw2100]

What would be considered a normal or healthy reading off a 12V battery, and what would be considered a borderline or weak one?

Thanks.

 

[JRP3]

At rest with no load it should be at least around 12.65V, 12.75-13V is better. Caveat, I've had some bad batteries that showed a "surface" charge of 12.7V but had no capacity at all, so a load test would be required to eliminate that possibility, though it's a rare occurrence.

 

[Andyw2100]

At rest with no load it should be at least around 12.65V, 12.75-13V is better. Caveat, I've had some bad batteries that showed a "surface" charge of 12.7V but had no capacity at all, so a load test would be required to eliminate that possibility, though it's a rare occurrence.

Thanks!

 

[SPXMike]

I have a 2013 CPO P85+ I picked up last September. A month ago in my garage car would not start - typical three 12v messages. A couple hours later, after the loaner and tow truck showed up, it started. I wanted them to look at it, and the loaner was a P90D (how nice), so we flat-bed to the SC in Buena Park. After three days they could not replicate the problem, but told me they would monitor the car for a week and let me know if they saw anything. No problems until this morning. Car was not plugged in overnight (still had 200 mi range as of last night) and would not start. I typically plug the car in almost every night. This time I used the great info in this forum to investigate 12v. Voltage was down to 12.1 VDC (not good). I called roadside service and they offered to tow but I wanted to see if the car would wake up after it warmed up a bit. An hour or so later car regained full function, voltage was 12.3 VDC (still too low). I will take to SC tomorrow, see what kind of a loaner I can get (wonder if that multicolor red P90D is still hanging around?) and let them have at it. The common thread here seems to be 1. did not have the car plugged in overnight, and 2. garage was a little cool. Yes I know, southern California, and 50F is nowhere near to being cool, but the car doesn't seem to like it. I know there have been a lot of changes to get the vampire loads down so the car sleeps better and doesn't beat up the 12v battery so much but something is wrong and now I think I can recreate it.

 

[SPXMike]

Uplate: 12v is at 12.5 but now the car won't start. I'm at my wits end. The car will do everything but start. When the car started at 12.3 v I plugged it back in. Then I unplugged it a few hours later and tried to start. Car won't start. Voltage is higher than before - it's now 12.5v.. I can't plug it back in. The ring around the socket is red so i'm locked out. So frustrating. Hopefully the service center can figure this out - this is the second time. This is by far the most awesome, most expensive, and most unreliable car I have ever owned.

 

[kennybobby]

Those low 12V battery voltages indicate a weak or worn out battery--how come it wasn't or hasn't been changed out with a fresh one? The open circuit voltage may look okay, but a weak lead-acid will fold under load.

 

[SPXMike]

Thanks Kenny. Now this morning the car starts! We'll see what happens at the service center.

 

[Footbag]

A ranger indicated to me that a firmware update in the last ~6 months has addressed the 12v problem (no further details given). It was stressed that 12v's in use prior to the update may still fail early, but basically cars produced recently should no longer have this ~annual 12v issue. Has anyone else heard anything similar (sorry, haven't read the entire thread)?

 

[jerry33]

A ranger indicated to me that a firmware update in the last ~6 months has addressed the 12v problem (no further details given). It was stressed that 12v's in use prior to the update may still fail early, but basically cars produced recently should no longer have this ~annual 12v issue. Has anyone else heard anything similar (sorry, haven't read the entire thread)?

I haven't heard one way or the other but there is only so much blood in a turnip and that dinky 12V battery is a petty small turnip.