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Thread: How many watts safely out of 12 the volt outlet?

  1. #1

    How many watts safely out of 12 the volt outlet?

    Is the 12 volt outlet tied into the battery pack so that it could be used for an extensive period of time without causing damage so long as the amps are kept within limit and you do not run down the battery pack? For instance, say you are at a nearby weekend cabin without electricity and you want to run a low amperage radio from the 12 volt socket. Assuming you watch the battery pack charge level and maintain it high enough to comfortably get back to a recharge location, would you be causing any problem? The manual specifies the maximum amps that can be drawn from the 12 volt connection, but I have seen no mention of the maximum watts (or kilowatts) that can be safely drawn.

  2. #2
    mod squad TEG's Avatar
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    Not really an answer, but some thoughts:

    Yeah, I would think you could run it for a long long time having the DC/DC converter just slowly draining your traction pack.
    As had been mentioned elsewhere, those 12V loads are just a tiny fraction of the power that is used when actually driving, so a pack full of charge that could get you 200+ miles of driving is probably good for months of little 12V load. Well lets say a portable radio was ~2watts average continuous (although the range could vary greatly), then your load is .002kW which gives over 25,000 hours from a 53kWh pack. Or over a thousand days. In any case, this fuzzy math based on a speculative load, but the example shows that I think you could possibly plug in a small radio and run it for years before it drained the pack! (I bet the pack would run itself down quicker just running on-board computers, and temperature control systems.)

    I don't know all the particulars, but I think the way the 12V is derived differs between 2008 and 2010+ models, so there could be some differences there.

    Best to check with a Tesla tech, but I suspect you could get 12V power for as long as you needed during a short trip.
    Last edited by TEG; 2011-01-26 at 11:52 PM.

  3. #3
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    My manual (2.0) says it's good for a maximum of 10A or 125W, but there is nothing about a limit on maximum energy draw (i.e., kWh).

    This post (link) says that the outlet turns off when/after the car turns off, but I guess that may vary version to version or might be changed with firmware changes.
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    2010 2.0 Roadster Sport
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    Based on the question in the initial post the subject should probably be:
    How many kWh safely out of the 12 volt outlet?
    Or maybe better:
    12 volt outlet usability/capacity when the car is off
    It is so choice. If you have the means, I highly recommend picking one up.
    - Ferris Bueller about the 1961 Ferrari 250GT Spyder California
    - Me about the Tesla Roadster

    I live my life 240 [ideal] miles at a time.
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    KWH-PWR#1349Sprt,S Sig#96 scott451's Avatar
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    Quote Originally Posted by tennis_trs View Post
    Based on the question in the initial post the subject should probably be:
    How many kWh safely out of the 12 volt outlet?
    Or maybe better:
    12 volt outlet usability/capacity when the car is off
    zero. Because the 12V outlet is off when the car is off. the 12V outlet runs off of Vaps in the ESS. The 12V outlet will stay on for a ~5minutes after the car is off and then turn off when the car goes to sleep. However, if the ESS is at high states of charge or the battery temp is above 30*C the pump will run continuously, causing the 12V outlet to stay on. The 12V outlet is also on when the car is charging.

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    Roadster 919, S 2006 Doug_G's Avatar
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    If no cooling is required, when in storage the car uses something like 300 Wh per day, by my estimation. At maximum rated 12V current you would consume 1,500 Wh per day. Even at that rate it would take a month to drain the pack. So modest use of the 12V outlet for a weekend would be no big deal, if you can keep the car powered up...

  7. #7
    2010 2.0 Roadster Sport
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    Quote Originally Posted by Doug_G View Post
    ...At maximum rated 12V current you would consume 1,500 Wh per day...
    125W*24hr/day = 3,000 Wh per day
    Still fairly small.
    It is so choice. If you have the means, I highly recommend picking one up.
    - Ferris Bueller about the 1961 Ferrari 250GT Spyder California
    - Me about the Tesla Roadster

    I live my life 240 [ideal] miles at a time.
    - Paraphrasing Dom in The Fast and the Furious

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