Which is why I was stunned when I asked them to switch out batteries under warranty and they said they ran tests on the current and it was still "in spec". They literally told me if I want to play the radio I must start the engine. I didn't fight it since I had already ordered my Model S at that point. My trips weren't necessarily short either. 11 miles each way to and from work should be sufficient to charge your battery. Ironic that I'm still running into 12V battery problems with my Tesla too.
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Which is why I was stunned when I asked them to switch out batteries under warranty and they said they ran tests on the current and it was still "in spec". They literally told me if I want to play the radio I must start the engine. I didn't fight it since I had already ordered my Model S at that point. My trips weren't necessarily short either. 11 miles each way to and from work should be sufficient to charge your battery. Ironic that I'm still running into 12V battery problems with my Tesla too.
JRP3
Hyperactive Member
You ain't kidding. I returned to my parking garage this evening after work to an unresponsive car :crying:
i guess swapping to a fresh 12v battery didn't solve the problem. Put in a trouble call with Barry. I'm really wishing they already had the P85 loaners in service. Now I'm gonna have to drive some piece of doodoo rental car for some indefinite period of time...
Exact same experience with my BMW. Within the first few months of ownership I took the car to drive in theater. The battery lasted 2.5 hours. Fast forward 2 years, and I get the warning in 3-5 minutes. I've even tried putting a battery charger on the car while parked overnight and it didn't help.
JRP3
Hyperactive Member
This is really troubling. It's quite obvious that this is not a "bad batch of 12V batteries" and that they are wasting a lot of time with a problem that doesn't seem to exist in other OEM EV's, or my home conversion EV. First of all the 12V battery should be easily accessible, and second the car seems to be killing them. Come on Tesla, to quote Elon: "Your sh!t is not together"
If you own a Tesla, purchase a plug-in VOLTMETER for the POWER SOCKET, and then don't leave home without measuring the voltage!! My lowest reading so far is 12.9 volts which is near the low end of the expected range. Under 12.6v for any extended period would be cause for concern, so call TM so they can do a remote scan of your system.
Remember: the 12 v battery includes a special circuit inside the battery case, so this component can fail as well as the lead-acid battery proper.
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Remember: the 12 v battery includes a special circuit inside the battery case, so this component can fail as well as the lead-acid battery proper.
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Al Sherman
It's about THIS car.
I did and am checking it regularly since the swap of the dead 12 volt. It's been 3 weeks (as much time as it took the first one to fail) and I have not seen less than 13.4-13.6.
JRP3
Hyperactive Member
That pretty much confirms for me that the power socket is indeed connected to the 12V battery circuit since a straight output from the DC/DC should be steady at a higher voltage. That's also why I think they have a two channel DC/DC converter so most of the accessory voltage can be higher and steady without worrying about overcharging the 12V battery. I'd be interested in knowing what the power socket voltage does when the car is turned on, and accessories are turned on, like head lights and climate control.
For me, in all those situations, it has been ranging between 13.36 and 13.54 since I got the car during my daily/random sampling as measured via the lighter socket.
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Troubling indeed. Sorry to hear it Stephen. Hope they get it sorted out and soon.
@JRP3: My headlights are always ON but I'll watch for any v drop next time I test AC. AC has zero utility up here; simpler & more efficient simply to open a window slightly. PWR SOCKET is always ON in ModelS so I pull voltmeter out just a bit to disconnect it when not in use.
Climbing into '"car off" car shows 14.7 volts which drops to 13.8v immediately when brake pedal is pressed (sound of pump on firewall).
Lead-acid battery is easiest way to get a 'regulated' voltage source. If there is a 2nd 12v circuit the heavy loads would self-regulate it. Do you think I could build a 'batt eliminator' using the pair of 1.0 farad caps I just got? That would be a worthwhile addition to the frunk. Would need to design a solid state regulator of some sort.
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Climbing into '"car off" car shows 14.7 volts which drops to 13.8v immediately when brake pedal is pressed (sound of pump on firewall).
Lead-acid battery is easiest way to get a 'regulated' voltage source. If there is a 2nd 12v circuit the heavy loads would self-regulate it. Do you think I could build a 'batt eliminator' using the pair of 1.0 farad caps I just got? That would be a worthwhile addition to the frunk. Would need to design a solid state regulator of some sort.
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I'm looking at the MS (currently a deposit on the MX) and would want to have a few lights hooked up to the 12V battery. They would be low draw LED lights that would run infrequently and have an on/off switch so I could shut them off. The local service center said they could install them but nobody seems to be sure if the main battery pack will recharge the 12V if it were to get low. Would this work for me? I would not run them if I were getting low on range but for times where I had excess range would this cause a problem? Thanks!
JRP3
Hyperactive Member
When you get in the car, can you turn the A/C on high with full fan before applying the brakes? My guess is the brake vacuum pump would be wired to the 12V battery for backup in case of power failure but something like the A/C might not be. Also I've heard it's good to run the A/C once in a while if you're in an area where you don't normally need it to keep everything lubricated.
The DC/DC should be regulating the voltage.
I don't think that would give you enough capacity to eliminate the battery, you'd need a much larger capacitor bank.
The DC/DC in the car is what keeps the 12V battery charged up from the main pack, so it should not be a problem.
JRP3
Hyperactive Member
Musk just mentioned the 12V battery in the conference call. Said they ordered the battery from a US supplier and it was outsourced and they ended up with a bad product. Not sure that accounts for the repeated replacements, unless they are putting in another bad battery from the same supplier, which would not make any sense.
Not true. See my posting #221 where I posted a graph that shows the 12V periodicaly cycling between about 13.5 and 12.6 volts. The DC/DC converter runs whenever the 12V battery voltage drops below 12.6 volts. As frar as I know no other manufacturers electric vehicle does this.
JRP3
Hyperactive Member
Other OEM's use a larger more conventional 12V I think, but I'd still expect the DC/DC to keep it topped off. Unless they shut down the DC/DC to kill all vampire loads.
Update: Not resolved yet, but working on it. Removed nose cone and jumped with 12v battery to get her started so we could drive her to the service center instead of the shame of a flatbed. This was during rush hour traffic and the journey takes us through the main corridor for those trying to make it home after work so there would have been many thousands of eyeballs seeing it on a flatbed, so very grateful that she was driveable. Made it to the service center though I did get a couple of warnings of "car needs service, may not be able to restart" just before I got there. Got my Enterprise rental car (Mazda 3) and they promised to make it right for good this time when they fix it. Hopefully it won't take too long.
As a cautionary tale for others, here were the symptoms (in other words, not zero warning, at least in my case):
Display on the dash says "Car needs service, 12v battery low" and disappears after 5 seconds or so. Your car will likely fail within a 24 hour period. Be prepared for it and of course take action right away to fix it. It happened both times this way for me.
When I get the official diagnosis/fix from Tesla I'll post it up.
As a cautionary tale for others, here were the symptoms (in other words, not zero warning, at least in my case):
Display on the dash says "Car needs service, 12v battery low" and disappears after 5 seconds or so. Your car will likely fail within a 24 hour period. Be prepared for it and of course take action right away to fix it. It happened both times this way for me.
When I get the official diagnosis/fix from Tesla I'll post it up.
Isn't it kind of silly for Tesla to not think through this failure scenario? I hope they address this in a design change in future model revisions - either an easier way of attaching jumper cables, or a button to enable the DC-DC converter to supply needed initial power.
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