Cigarette Lighter and USB Adapters

[Marc Boucher]

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 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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