Most cars have a 120W limit on the accessory 12V plug - the connector can't safely handle more than that.
Check this thread out:
12 volt accessories?
Last edited by smoothoperator; 04-18-2012 at 12:32 PM. Reason: added link and reference
Yes, but I expect the 12V battery is constantly fed power while the car is operating. So the power comes from the ESS. At most the 12V battery is acting like a (super)capacitor.
We actually manufacture a motor control system that runs that way. It has a 12V sealed battery - identical to the one in the Roadster - that is essentially trickle charged all the time. It doesn't really provide power to the electronics except in two situations. If the mains power goes out, it provides emergency backup power, so everything can shut down safely. Also if the control system is hooked to a larger DC motor, the battery essentially acts as a capacitor and absorbs the motor startup surge.
Hopefully Tesla will have a better 12V battery monitoring system than the Prius (or the Leaf from what I've read on the forums). The problem with the 12V battery is that because there is no starter motor, there is no warning when it starts to get weak. in the Prius this can cause odd behaviour and sometimes cause it to throw codes. In one case the Toyota dealer told the owner that they would need a new traction battery, new transaxle, and new inverter. Fortunately the owner posted this in one of the groups and followed the groups instructions to replace the 12V battery and see if the codes didn't go away. They did. On my 2004 at five years I replaced the battery and found that it had two dead cells. I never had to do a jumpstart nor was there any odd behaviour.
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Keep in mind that 1.5's seem to have a different arrangement for the aux 12v compared to 2.0 & 2.5's...
For the 2.x's it is my understanding that the aux 12v battery is primarily there to keep things like the headlights and door locks working for a while if the ESS / DC->DC should stop providing power. This could be due to it failing, running out of charge, or being disconnected such as in an accident. If your ESS got damaged in an accident it might be good for the headlights and door unlocks to keep working - so, for instance, someone could see the car, and open the door to help you out.
Scott451 in this thread:
12 volt accessories?
Listed a comprehensive list of electronics that work off the ESS and ones that work off the Lead Acid battery. Quote below:
Scott has certainly dug further into the Roadster than any non-Tesla (uh, formerly non-Tesla) person I know of. But saying it "runs off the battery" might really mean "runs off the Vsb bus", and depending on how things work it might not draw primary power from the lead-acid battery.
Basically I'm saying I'm not convinced either way at this point.
Specifically, is it safe to use something like:
Amazon.com: BESTEK 150w power inverter car dc 12v to 110v ac inverter dc adapter laptop charger notebook adapter dc charger ac adapter usb charger Dual USB 3.1A 1511C: Cell Phones Accessories
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