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12 volt accessories?

billytuffnuts

New Member
Dec 27, 2010
2
0
New here to the Tesla community. I don't own one unfortunately, but I've become pretty interested in them, finding out how they work etc...

I was curious if anybody would be able to tell me if these cars have some sort of 12 volt auxiliary battery system that runs the accessories (wipers, headlights, etc...) like on hybrids or if they are just ran off the high voltage battery pack?
 

cinergi

Active Member
Sep 17, 2010
2,176
41
MA
New here to the Tesla community. I don't own one unfortunately, but I've become pretty interested in them, finding out how they work etc...

I was curious if anybody would be able to tell me if these cars have some sort of 12 volt auxiliary battery system that runs the accessories (wipers, headlights, etc...) like on hybrids or if they are just ran off the high voltage battery pack?

Welcome!

The newer models of the Roadster use a DC-DC converter which provides 12V power to all the accessories. There is a small 12V battery which is used to power the VMS (Vehicle Management System) and for unlocking the doors.
 

billytuffnuts

New Member
Dec 27, 2010
2
0
Welcome!

The newer models of the Roadster use a DC-DC converter which provides 12V power to all the accessories. There is a small 12V battery which is used to power the VMS (Vehicle Management System) and for unlocking the doors.

So then is the DC to DC converter constantly trying to keep the 12v battery fully charged as the vehicle is running (using these 12v accessories), similar to how an alternator maintains a batterys charge on an ICE equipped vehicle?
 

TEG

Teslafanatic
Aug 20, 2006
21,965
9,194
All of them have a 12V system for some standard things like radio, wiper motors, etc.

The ~375V main "traction pack" can power the A/C drive motor, and (I think) also the heater and possibly air-conditioning compressor.


Toyota Hybrids like the Prius have an Aux 42V system for things like power steering, but I don't think the Roadster has that.
 

scott451

KWH-PWR#1349Sprt,S Sig#96
Apr 2, 2009
258
2
Palo Alto
Welcome!

The newer models of the Roadster use a DC-DC converter which provides 12V power to all the accessories. There is a small 12V battery which is used to power the VMS (Vehicle Management System) and for unlocking the doors.

I believe there are two 12V power systems in all Roadsters, Vaps and Vsb. Vaps appears to be used by the major EV systems in the car (PEM, HVAC, etc). The Vsb (secondary battery?) seems to be used for all car critical systems (VMS,ABS, SRS, doors, alarm, etc). Some systems (like the VDS and possibly the VMS) appear to have the ability to draw power from either, if one should fail.

I'm not sure which one the radio runs on, but I'll check (when I get back on 1/7/11).
 

tennis_trs

2010 2.0 Roadster Sport
Aug 25, 2009
302
7
Regarding the 12V outlet in the passenger area. The (2.0) Owner's Manual says:
Note: The power socket is suitable for
accessories requiring up to 10A or a
maximum of 125 watts.
When I went looking for an accessory that I wanted to buy to use in the outlet I saw that some devices, designed to connect to car 12V (cigarette type) outlets, are rated to draw more than 10A. I think I saw something like 12A or 15A and the box for the device noted that some older outlets only supported 10A (and apparently some newer ones support the higher current I saw).
 

TEG

Teslafanatic
Aug 20, 2006
21,965
9,194
I don't think the Roadster is designed to have a lot of extra 12V amperage capacity. Probably not a good car to plug in an inverter and try to run appliances off of the lighter socket.
Apparently some custom stereo shops ran into the output limits when trying to add external amplifiers for high end audio systems.

There are 15amp+ 12V devices sold out there like heaters and such:
http://www.amazon.com/RoadPro-RPSL-681-Direct-Hook-Up-Ceramic/dp/B0013TM0Z0/ref=pd_sbs_k_3
http://www.12volt-travel.com/cuisinart-quick-brew-4-cup-12-volt-coffee-maker-p-7782.html
http://www.12volt-travel.com/12-volt-hair-dryer-with-folding-handle-p-5902.html
http://www.12volt-travel.com/12-volt-oven-and-pizza-maker-p-5906.html
http://www.12volt-travel.com/12-vol...ylish-chrome-finish-black-accents-p-5929.html

(To be clear, I think it would NOT be good to use any of those above high current draw devices in a Roadster)
 
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cinergi

Active Member
Sep 17, 2010
2,176
41
MA
I believe there are two 12V power systems in all Roadsters, Vaps and Vsb. Vaps appears to be used by the major EV systems in the car (PEM, HVAC, etc). The Vsb (secondary battery?) seems to be used for all car critical systems (VMS,ABS, SRS, doors, alarm, etc). Some systems (like the VDS and possibly the VMS) appear to have the ability to draw power from either, if one should fail.

I'm not sure which one the radio runs on, but I'll check (when I get back on 1/7/11).

The A/C compressor is labeled 400 volts (AND 12 volts). The cabin heat draws several KW, so that's also not off any 12V system. One of the NY techs told me the small 12V lead-acid battery (See this thread) only runs the critical systems like the locks and VMS (could have been VDS, but I'm not sure that makes sense). There are the contactors for electrically connecting the 375V traction system to either the charger or the motor -- those used to be powered by said lead-acid battery but it proved to be too weak in the cold and was moved to some other system (according to the tech) -- perhaps that's the "Vaps" system?
BTW, there's a DC-DC (375V - 12V) converter next to the compressor in the front.
I just noticed the radiator fans are 12V. I also noticed that the DC-DC converter is on (there's a power light) even though the car isn't charging or driving.
 

scott451

KWH-PWR#1349Sprt,S Sig#96
Apr 2, 2009
258
2
Palo Alto
The A/C compressor is labeled 400 volts (AND 12 volts). The cabin heat draws several KW, so that's also not off any 12V system.
The HVAC runs off the APS 12V supply to control the 400V for both the A/C compressor and the resistive heater. The box next to the compressor in front, is not the DC-DC converter for the 12V system in the car. It is a DC controller that converts the 275V-410V from the ESS to a variable voltage for the resistive heater and a variable voltage for the muiltspeed compressor. (It possible that the 2010 compressor is an AC motor, so the box would also be a variable frequency inverter)
One of the NY techs told me the small 12V lead-acid battery (See this thread)
only runs the critical systems like the locks and VMS (could have been VDS, but I'm not sure that makes sense).
The battery for the 2010 is located behind the right headlamp. I believe this battery is there because of DOT requirements. The door locks do not appear to run off this battery (b/c when the Vaps is off, the locks do not work). ABS, SRS, VDS and VMS do appear to run off this battery. The VDS can run off either Vaps or Vsb because it can be use to turn off the primary +12V supply (Vaps) while running off of (Vsb). The techs always turn off Vaps via the VDS whenever they are working on anything electrical in the car. (that would imply that all the 400V contactors are controlled by Vaps not Vsb/small battery)
There are the contactors for electrically connecting the 375V traction system to either the charger or the motor -- those used to be powered by said lead-acid battery but it proved to be too weak in the cold and was moved to some other system (according to the tech) -- perhaps that's the "Vaps" system?
Yes. Probably moved to Vaps because when it is off, there would be no 400V or high current 12V present. There are multiple contactors in the car. I don't believe there is a contactor between the PEM and the motor because of the huge (~700A) current it would have to handle. In the 2008 there is a AC propulsion patent that describes how the motor is actually used as an inductor for the charging system.
BTW, there's a DC-DC (375V - 12V) converter next to the compressor in the front.
I just noticed the radiator fans are 12V. I also noticed that the DC-DC converter is on (there's a power light) even though the car isn't charging or driving.
No. The box you refer to is the power controller for the HVAC system described above. The DC-DC 400V to 12V converter is in the ESS battery pack. This dual DC-DC converter supplies the [email protected] to run the 12V systems in the car and a secondary [email protected] supply for more critical and always on devices (e.g. radio +Battery line).
 
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William3

Member
Aug 7, 2008
174
6
How does the lead acid 12V battery on the 2010 Roadsters get charged? Would it be safe to run an aftermarket stereo off this 12V lead acid battery?
 

TEG

Teslafanatic
Aug 20, 2006
21,965
9,194
How does the lead acid 12V battery on the 2010 Roadsters get charged? Would it be safe to run an aftermarket stereo off this 12V lead acid battery?

<speculative answer>I assume that the DC/DC converter from the traction pack recharges it. Also it is a rather small battery, so I wouldn't count on having it provide a lock of backup power for a large stereo upgrade. I recall hearing that it is a motorcycle battery.</speculative answer>
 

TEG

Teslafanatic
Aug 20, 2006
21,965
9,194
Meh (I think this is the first time I ever used that expression), you know what I meant. A battery mostly sold for motorcycle use.
Also too small to work effectively as a primary battery for an ICE vehicle that would need to run a starter motor.

By the way, it probably meets this definition of a motorcycle battery:
http://www.whybike.com/motorcycle107.htm
(But so do most 'car batteries' if you could fit them in a motorcycle.)
 

Doug_G

Lead Moderator
Apr 2, 2010
17,882
3,392
Ottawa, Canada
Here's a photo of the battery in question:
 

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TEG

Teslafanatic
Aug 20, 2006
21,965
9,194
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cinergi

Active Member
Sep 17, 2010
2,176
41
MA
Good stuff scott451 -- thanks! I'll have to correct MY sources now (don't quite remember who, but it was a Tesla employee) :)

BTW, I've noticed the 12V cig lighter powers on whenever the car "wakes up" e.g. to charge. I have a radar detector with bluetooth interface and I occasionally notice it's connected to my iPhone while it's parked outside :) I'd assume the entire 12V system is on at that time.
 

scott451

KWH-PWR#1349Sprt,S Sig#96
Apr 2, 2009
258
2
Palo Alto
Good stuff scott451 -- thanks! I'll have to correct MY sources now (don't quite remember who, but it was a Tesla employee) :)

BTW, I've noticed the 12V cig lighter powers on whenever the car "wakes up" e.g. to charge. I have a radar detector with bluetooth interface and I occasionally notice it's connected to my iPhone while it's parked outside :) I'd assume the entire 12V system is on at that time.
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. I found out the hard way while trying to charge my iPhone over night. I plugged in the phone to the 12V cig, locked the car and could see through the window that the phone was charging. At the time, I was unaware that the 12V cig would turn off 5mins later when the car went to sleep. The next morning I found my iPhone with 5min of charge. The week before I did the same thing, but left the car on the UMC charger overnight. While the car was charging its battery, the 12V cig was on, so I got a full charge on my iPhone.
 
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vfx

Well-Known Member
Aug 18, 2006
14,790
47
CA CA
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?
 

stenkb

Roadster 938 Model S 5957 Model X ?
Nov 23, 2009
218
14
Lethbridge, Alberta
Kind of on topic: I needed to find a constant power source on the car for an add-on that was installed and the only fuse I could find that had continous power when the car was off was the 7.5 A alarm fuse. All others that I tried - turn off (eg. power adapter plug in, etc.).

After about 3 minutes with the car turned off the power adapter plug loses power - I sat in the car and watched it happen. If you open a door or anything you get about 3 min of power again until it loses power again.
 
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