12v battery issue explanation, sort of...

[wycolo]

Here's the report from Denver Service as to why my MS died as soon as it parked at the Glenwood Springs, CO SuperCharger: The 12 volt pos terminal loosened up over the 7 week period since newly installed. That is the terminal visible from under the frunk fuse cover, not the neg terminal which is hidden behind the battery. And which I never touched myself as I worked with live voltages during my frunk terminal modification. So bolt not tightened sufficiently when battery replaced.

With 8 people scratching their heads over this one it just had to be something out of left field. Explains the total lack of screen errors while the car was being driven. The final step in my project is a mechanical frunk release; too bad it wasn't completed for Plug-In Weekend!
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[Mayhemm]

So your 12V wasn't actually dead? One of the terminals had just worked itself loose enough to cut power?

 

[wycolo]

Not 'worked itself loose' but bolt installed with totally wrong torque when fresh 12v battery installed recently. Since the posts are solid lead it is almost impossible to over-torque the bolts such that they would break later. The lead (as in Pb, the metal) yields, resetting the torque. Had to be way under torqued, never biting into the lead as intended. Or simply forgot to tighten the second bolt. No use of HVAC but you would think the brake booster pump would draw some decent current on a regular basis and trigger a fault. Anyhoo, glad that all circuits and components are aok and that it happened just where it did.
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[Botbldr45]

[SUP][/SUP]I am about to order my MS and move to Sedona which is 150 miles or so from nearest service center. My 12 volt battery on my Roadster was replaced once about two years ago and checked at yearly service visits...... No problems.

Have there been upgrades or changes in MS that make this system more stable. I would hate to need towing to Scottsdale from Sedona with a MS .....:scared:

On the east coast the Ranger visits are limited to 90 miles out...... Bummer! From what thread indicates Ranger can do it but 150 miles out May require a tow.

Question: have there been improvements made to 12 volt system, battery in particular, to anyone's knowledge?

 

[zwede]

The 12V battery in the MS has been revised several times over the last year and a half. I don't think we know yet whether the current version finally solved the problem.

 

[wycolo]

The answer is the lack of complaints about it here on TMC.
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[sbronle1]

Excellent observation. My MS is due to arrive in three weeks. I have had to replace the battery in my current GTI twice in the last three years. Easy answer to my problem was to buy a $35 small battery pack that can be easily stored and needs a recharge about every 6-8 months. Good for at least 3 restarts before needing to be recharged. Also ordered the flat tire repair device from Tesla for $50 as there is no spare and I care not to wait for hours for a service dispatch. Small issues but probably not significant as wycolo pointed out as they have not recently appeared on the forum.

 

[ggr]

Our Model S went in on Wednesday to get the glove box door unstuck (apparently a common problem with the early cars, they redesigned the latch, so the service ticket says "replaced glove box"). Anyway, last night I went to plug it in and it was mostly dead. Called the help line and they said that the 12V battery is discharged, and it just needs a jump start. It was last fully charged on Sunday... interestingly our charger died too. Surely the 12V should last longer than 5 days! The car was plugged in and charging started a couple of times between Sunday and last night, just to check whether the charger was working, and also at the service center for long enough to gain about 10 miles of range.

 

[wycolo]

So did you try to jump start the MS? Time is of the essence!
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[ggr]

So did you try to jump start the MS? Time is of the essence!
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Yes, this morning the guy from the service center arrived in a loaner with a battery-pack jumper thing. The plan was to start my car and drive it back to the service center. He connected the jumper, and the car woke up and started but then went dark again before he could move it. He disconnected the jumper, waited a minute, and reconnected it again; the car woke up long enough to put it in tow mode. So we rolled it out onto the street, and he sat in it with his foot on the brake while I got wheel chocks. An hour later it was flat-bedded to the service center.

I just got a call, apparently the problem is that the HV (main) battery was not switching power through to recharge the 12V battery. It looks like I'll get a new HV battery out of the process.

 

[wraithnot]

Yes, this morning the guy from the service center arrived in a loaner with a battery-pack jumper thing. The plan was to start my car and drive it back to the service center. He connected the jumper, and the car woke up and started but then went dark again before he could move it. He disconnected the jumper, waited a minute, and reconnected it again; the car woke up long enough to put it in tow mode. So we rolled it out onto the street, and he sat in it with his foot on the brake while I got wheel chocks. An hour later it was flat-bedded to the service center.

I just got a call, apparently the problem is that the HV (main) battery was not switching power through to recharge the 12V battery. It looks like I'll get a new HV battery out of the process.

The exact same thing happened to me about two weeks ago: 12V battery issue- stranded at Mt Shasta supercharger

With any luck they've redesigned the faulty component and the replacement pack won't have a similar problem in the future.

 

[Mayhemm]

I just got a call, apparently the problem is that the HV (main) battery was not switching power through to recharge the 12V battery. It looks like I'll get a new HV battery out of the process.

I thought using the HV battery to recharge the 12V was what the DC-to-DC converter was for? Wouldn't it make more sense to replace that rather than the whole $40K HV Battery?

 

[jerry33]

I thought using the HV battery to recharge the 12V was what the DC-to-DC converter was for? Wouldn't it make more sense to replace that rather than the whole $40K HV Battery?

I don't think so. Consider the way Tesla does it. Replacing the entire assembly and sending it back to be refurbished, means the cost is really only the freight and the labour for the short time it takes to replace the unit. It also has a much better chance of success because if the diagnosis was incorrect replacing the entire pack means there is an almost 100% chance that a second visit won't be required. Because the pack will be reused, the cost of materials is as close to zero as possible.

Of course, this method doesn't work in a dealer model as there is limited opportunity for service centre profit from repeated visits to fix the same problem.

 

[wycolo]

The MS Battery Pack contains a relay and associated control circuitry. Its not just a box with batteries strung together amongst the cooling tubes. So when those electronics fail the whole shebang gets replaced. Not the most logical design, it would seem.
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[scott jones]

i just got in my car after a long morning of golfing. And the dash noted, "12v Battery Needs Service." And the emergency (!) note also said Battery need to be Replaced soon. I just called Tesla, and they are closed on Fathers day. FYI, I just got my S85 3 weeks ago in Cincinatti. Unfortunately where I live in Indianapolis doesn't have a service center (yet). So they put in a service call and they'll be contacting me tomorrow. The car still got me home, but unfortunately I can't tell if it'll work in the morning, or if I should drive it as there is no battery meter scale, or a "it's about to die" warning indicator... HURRY THE HELL UP". I did do what a few have suggested because it's parked nose first in my garage. The main battery pack is plugged in, and I put it in Neutral and turned the car off to keep it in neutral in case it needs to be towed. We'll see what happens tomorrow.

 

[Mayhemm]

The main battery pack is plugged in, and I put it in Neutral and turned the car off to keep it in neutral in case it needs to be towed. We'll see what happens tomorrow.

Since you're still fairly new to the car you may not be aware that the recent versions of the software have what's called a "tow mode", which basically leaves the car in neutral without engaging the emergency brake. It can be found on the "E-brake and Power-off" screen. Not sure if it's any different from what you already did, but it does give you a dedicated indicator light on the dash so you know it is active and it will remain so until you manually put the vehicle in park.

Make sure your garage is reasonably level before engaging tow mode though, as the car will be free-rolling and could hit something/someone if left on an incline.

 

[donv]

Why does the Model S even have a 12v battery at all? I'm guessing some sort of regulatory requirement?

 

[Mayhemm]

Why does the Model S even have a 12v battery at all? I'm guessing some sort of regulatory requirement?

I don't believe so. The 12V is necessary to run all of the accessories like the screens, lamps and climate controls. If Tesla didn't use a 12V for this, they would have to re-engineer all the electronics to run off the main battery (different voltage). With a 12V in place, they can use off-the-shelf parts, greatly reducing their expense.

Much of the heavy equipment where I work uses 24V so you either have to step it down yourself or use ridiculously-expensive 24V products (think $800 for a cassette deck). Model S would be the same if not worse.

 

[JRP3]

They already have a DC/DC converter that steps pack voltage down to 12V, they could have set it up that even without a 12V battery everything would still work directly from the converter. In fact they should have set it up that way. I consider this a design flaw.

 

[jkliu47]

Why does the Model S even have a 12v battery at all? I'm guessing some sort of regulatory requirement?

Kinda like a PC/laptop has a small CMOS battery soldered onto the motherboard?