Cigarette Lighter and USB Adapters

[Mark Rosenkrantz]

Ah, I didn't realize that Audi wired the old lighters to +12V battery.
Well, at least they don't do that any longer!

On Sat, Dec 17, 2011 at 10:36 AM, Marc Boucher <mboucher70 at hotmail.com>wrote:

> The draw wouldn't be an issue when the car is running.  But some of the
> new cigarette lighter/USB adapters are made to mount flush with the surface
> and stay in permanently.  If memory serves, the cigarette lighter is
> powered on Audi permanently, not via the ignition switch.  Hence the
> question of power draw when its not delivering any power.
>
> Just being cautious because I had an experience with an aftermarket stereo
> years ago.  Most cars don't run the stereo unless the ignition is on.  The
> aftermarket Clarion unit drew enough energy to light up the display, even
> when off, to drain the battery significantly if the car wasn't driven for a
> few weeks.  I later read it was possible to wire the aftermarket stereo to
> be powered through a switched power, source, but the source of a switched
> positive to tap into wasn't trivial.
>
> MC
>
> ------------------------------**--------------------
> From: "Mark Rosenkrantz" <speedracer.mark at gmail.com>
> Sent: Saturday, December 17, 2011 8:53 AM
> To: "Ed Kellock" <ekellock at gmail.com>
> Cc: "Marc Boucher" <mboucher70 at hotmail.com>; <quattro at audifans.com>
> Subject: Re: Cigarette Lighter and USB Adapters
>
>
>  The adapter draw will be based on demand, plus conversion loss (heat)
>> which is dependent on the efficiency of the unit.  That said, even if you
>> double the theoretical 20W, 40W at 12.5V (which should be min. Voltage) is
>> only 3.2 Amps of current draw... Hardly an issue for a cigarette lighter.
>>
>> Mark Rosenkrantz
>> Typos sent from my iPad
>>
>> On Dec 17, 2011, at 1:01 AM, "Ed Kellock" <ekellock at gmail.com> wrote:
>>
>>  I believe the rear cig lighter is also disabled if you disable the rear
>>> windows from the drivers armrest console.
>>>
>>> Ed
>>>
>>>
>>>
>>> -----Original Message-----
>>> From: quattro-bounces at audifans.com [mailto:quattro-bounces@**
>>> audifans.com <quattro-bounces at audifans.com>] On
>>> Behalf Of Marc Boucher
>>> Sent: Friday, December 16, 2011 10:13 PM
>>> To: quattro at audifans.com
>>> Subject: Cigarette Lighter and USB Adapters
>>>
>>>
>>> Just noticed that the rear cigarette lighter stopped working in my 1990
>>> 100.
>>> Lighter is good, ground is good, but there's no power.  Fuse is good. Was
>>> wondering if anyone had experienced failures with this and knew the
>>> likely
>>> failure locations and/or repair.  (Preparing for some holiday road
>>> trips...Sister-in-law needs to keep nephew entertained/distracted with
>>> movies on long drives).
>>>
>>> On a related subject, this may be a little NAC, but I'm currently
>>> shopping
>>> for USB adapter for ipod/iphone/ipad, etc.. You can charge an iphone on
>>> as
>>> little as standard USB, ie 500mA.  On the other end, the max charge for
>>> an
>>> iPad is 2A.  And there are some lighter adapters that have two usb slots.
>>> Thus you can get adapters that put out
>>>
>>> as little as
>>> 500mA x 5V = 2.5 Watts
>>>
>>> or as much as
>>> 2A x 5V x 2 USB slots = 20 Watts.
>>>
>>> The question I have is, would an adapter that's plugged into the
>>> cigarette
>>> lighter draw power based on what it can supply, or based on what is
>>> demanded
>>> from it?
>>>
>>> ie
>>>
>>> assuming I've got the dual USB adapter, which can output as much as 20
>>> Watts, but I've got a single iPhone plugged in, which can draw a maximum
>>> of
>>> 5 Watts, is the draw on the car's electrical system going to be 5 Watts,
>>> or
>>> 20 Watts?
>>>
>>>
>>> Thanks
>>> MC
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>>
>>