12 volt accessories?

[cinergi]

Thank you for sharing Scott. I have a Magellan GPS plugged in the cig lighter socket. When I turn off the car it asks if i want to use the internal battery so i assumed the 12V shuts off. One night I let the GPS use it's own battery and figured it would be dead in the morning but it was on. I thought that was impressive but since the car was plugged in I guess the 12V plug was live.

So what about the "use internal battery?" screen on the GPS when the car is shut off? Well sometimes i see it come on when driving down the road. The "use battery?" screen stay on for about 3 to 5 seconds. I thought at first it was a loose 12V connection where it plugs in but am confident in that connection now and that the car is somehow-for some reason shutting the power off to the 12V momentarily. It still could be a loose connection somewhere in the car (1.5 cars do not have the 12V battery) but I wonder if it's a circuitry thing. That same sort of shut off may happen when the car is turned off.
?

Anyone else notice a similar while-driving loss of 12V power?

Not quite what you're describing, but I have noticed that when my ABS activates, the 12V system drops enough voltage that my radar detector shuts off (low-voltage battery shutoff). I wonder if yours is teetering on thinking low-voltage condition.

 

[vfx]

Not quite what you're describing, but I have noticed that when my ABS activates, the 12V system drops enough voltage that my radar detector shuts off (low-voltage battery shutoff). I wonder if yours is teetering on thinking low-voltage condition.

Sure, that could be it. It seems like it happens when I'm just driving but I'll look for an ABS coincidence.

 

[cinergi]

This just happened to me when regen re-enabled. As soon as the light on the dash disappeared, my radar detector reset. There must be certain system events that cause the 12V system to dip or something ...

 

[markwj]

Yes. The 12V cig lighter appears to run off Vaps. This causes a somewhat misleading user experience. To the user, it seems that the 12V cig lighter is always on, but it is not it. It only stays on for the first ~5min after the car is turned off.

Thanks for this. It was confusing the hell out of me.

 

[markwj]

Hmm... Looks like this:
http://www.sepbatteries.com/pt7b-4-power-sonic-battery.aspx

Interesting. We used to use large numbers of an almost identical battery for powering underwater 50watt lights while cave diving. We saw drops of about 30% burn-time after the first 100 or so discharges. Under heavy use, we'd change to new ones once a year or two. Admittedly, the environment was harsh (salt water, high humidity). Good news is that they are relatively cheap, and very simple to charge.

Nowadays, this has been replaced with Lithium Ion batteries and HID/LED lamps. Same burn time, an a much nicer light, for 1/4 the weight.

 

[Doug_G]

12V battery looks like this:

 

[zack]

I'm extremely curious about continuous 12VDC power for a sophisticated alarm system so I wrote to ask about it... here's the response I got today:

Zachary,
I have received a response from our engineering staff and it is highly likely that the alarm system will drain the Backup power source and you will get BPS problem faults, damage the Vehicle Management System or the Switch Pack. Hence this sort of a system is not recommended beyond the on board alarm system.
With this in mind they have requested the power consumption data of the alarm system for review.
If you have this information and can forward it to me I can pass it to our engineering staff.
Lawrence

 

[cinergi]

Anyone run a 12V air compressor from the accessory outlet? In my recent move, I had to get rid of my big 120V compressor and am looking for a portable alternative. I'd rather not use a rechargeable one (weight and stamina reasons), but all the ones I'm seeing say they consume ~14 amps and the outlet is rated for 10.

 

[ggr]

Anyone run a 12V air compressor from the accessory outlet? In my recent move, I had to get rid of my big 120V compressor and am looking for a portable alternative. I'd rather not use a rechargeable one (weight and stamina reasons), but all the ones I'm seeing say they consume ~14 amps and the outlet is rated for 10.

I have a little one that came with my Mercedes, and have run it from the Tesla without trouble. I don't know what current it draws though.

 

[smorgasbord]

12V battery ....

Finding out my high-tech Roadster needs a motorcycle battery is a major bummer.

 

[S-2000 Roadster]

I was told by a Seattle Tesla employee (sales or service, I can't remember) that one or two of the ESS sheets are used for auxiliary power, since the total ESS voltage is above 400 V. One sheet (9 series batteries) would be 27 V "empty" to 37 V, two sheets would be 54 V to 75 V. Now that I look at the numbers, using one or two sheets for a separate battery supply output would not really produce a convenient voltage - certainly not the 12 V nominal automotive standard that ranges from 11.8 V to 14.4 V or more.

Does anyone have more information about the auxiliary ESS output that uses only a sheet or two? ... and is this related to the 12 V accessories at all?

 

[Doug_G]

I was told that the ESS originally had an auxiliary 12V output for "emergency power", but that it was problematic so they introduced the 12V sealed lead-acid backup battery.

The main 12V supply comes through a DC-to-DC converter.

 

[S-2000 Roadster]

The main 12V supply comes through a DC-to-DC converter.

I wonder how hard it would be to upgrade the DC-DC converter for more current, perhaps even paralleling a second DC-DC converter for added systems. Trouble is, messing around in these areas likely voids the warranty, and is potentially very dangerous due to the high input voltages.

 

[TEG]

I recall conflicting reports about that "extra sheets for 12V power". Best I recall someone said "no, just DC/DC from the traction pack".
But, the newer models (2011+) have that extra 12V battery up front which is apparently a safety measure so things like the headlights and emergency flashers still function even if you run the "traction pack" all the way to empty. Might also be useful to boot up the car to start charging if you have an "empty" Roadster towed to a charging location. By the way, don't ever let the main pack get empty if you can help it. Not good for the cells.

 

[TEG]

I wonder how hard it would be to upgrade the DC-DC converter for more current, perhaps even paralleling a second DC-DC converter for added systems. Trouble is, messing around in these areas likely voids the warranty, and is potentially very dangerous due to the high input voltages.

Some of the aftermarket stereo shops resorted to stuffing an extra 12V lead-acid in the back to power their subwoofer amplifiers. Then they have a little 12V charger in back with an extra 120V cord dangling out so you have to recharge your stereo amp power source separately from the rest of the car. Kludgey and I wonder if the extra weight back there upsets the handling. Yes, a beefier DC/DC would be handy for customized Roadsters with monster stereos... But my understanding is that it would be very difficult to upgrade it.

 

[S-2000 Roadster]

By the way, what is a "traction pack?" I've heard the terms ESS (Energy Storage System) and battery pack, but now I'm seeing this term "traction pack."

 

[mnx]

They are all the same thing. Traction pack simply refers to the "battery" that propels the car. (or supplies juice to the motors).

- mnx

By the way, what is a "traction pack?" I've heard the terms ESS (Energy Storage System) and battery pack, but now I'm seeing this term "traction pack."

 

[scott451]

I was told by a Seattle Tesla employee (sales or service, I can't remember) that one or two of the ESS sheets are used for auxiliary power, since the total ESS voltage is above 400 V.

The above quote is clearly wrong. All of the sheets are exactly the same. If you were to draw power from one, you would unbalance the ESS pack. The DC/DC converter, inside the ESS, uses the 400V and converts it to two 12V outputs.

Does anyone have more information about the auxiliary ESS output that uses only a sheet or two? ... and is this related to the 12 V accessories at all?

(from the VDS) There are two 12V power supplies: Vaps and Vsb. Vaps is 13.5V (I think), and runs all the major 12V acceccsories. Vaps turns off when the car sleeps. Vsb is 12.5V and FWICT, is always on. Vsb runs things like the VMS, Alarm, VDS, and possibly the switch pack. Some modules (like the VDS) can run off either Vaps or Vsb.

 

[S-2000 Roadster]

The above quote is clearly wrong. All of the sheets are exactly the same. If you were to draw power from one, you would unbalance the ESS pack. The DC/DC converter, inside the ESS, uses the 400V and converts it to two 12V outputs.

I'm sure you're right about the actual configuration that's being used, but I just wanted to point out that there's nothing necessarily bad about an 'unbalanced' ESS pack. The sheets are in series, and their total voltage drops significantly when you floor the vehicle. There would certainly be some challenges if one sheet were providing more current than the rest, but there are most certainly other battery (charging) systems on the market which deal separately with series batteries as independent units.

Now that I think about it, I seem to recall that it was the older battery packs that had this one-or-two-sheet output, but that Tesla Motors retired this design. I was looking at a display battery in the service area when this "information" was offered. I'm not saying that I believe it, just that it is certainly within the realm of possibility.

The VehicleLogs show that each cell has its own voltage. Sometimes the variance is greater than other times, but even when it's vary narrow they're not all identical. 69*11*9 cells cannot always be perfectly balanced, and by separating out one or two series groups there would not be insurmountable problems with the slight voltage differences.

 

[scott451]

I'm sure you're right about the actual configuration that's being used, but I just wanted to point out that there's nothing necessarily bad about an 'unbalanced' ESS pack.

As the EV DIY folks on this forum can confirm, battery balance is very important. Every time your car gets serviced, Tesla runs a "bleed-test" which specifically measures the ESS balance. There are a number of tesla patents w.r.t ESS balancing. One of them describes how the car is constantly monitoring the battery balance.

Now that I think about it, I seem to recall that it was the older battery packs that had this one-or-two-sheet output, but that Tesla Motors retired this design. I was looking at a display battery in the service area when this "information" was offered.

doubtful, as this would seriously unbalance the pack.

The VehicleLogs show that each cell has its own voltage.

Not exactly. Each brick has it's own voltage. 69 cell make a brick. You cannot measure the voltage of an indivdual cell. The vehicle logs record the Average brick voltage, the min voltage, and the brick number of the min voltage. AFAIK, they don't record the max. The DIAG_ESS may have more info.

Sometimes the variance is greater than other times, but even when it's vary narrow they're not all identical. 69*11*9 cells cannot always be perfectly balanced, and by separating out one or two series groups there would not be insurmountable problems with the slight voltage differences.

Actually its 9*11 or 99 bricks that need to be balanced. I saw the bleed test once for sheet 11, the differences seemed to be around +/- 10-20 mV. Take a look at ahr.log and you can see how well the battery is balance. YMMV