Cigarette Lighter and USB Adapters

[Marc Boucher]

I ended up getting a neat little car USB adapter that was highly rated on 
Amazon.  Manufacturer designs it to essentially be almost flush so that it 
becomes a permanent part of the car, given that cigarette lighters aren't 
much used anymore.

Took some measurements of the USB adapter to see how much current it draws 
with nothing attached to it.  It draws 26mA.  Not a whopping amount, but its 
also not zero.  And the cigarette lighter on the Audi in question does in 
fact stay on all the time.  While 26mA isn't going to drain a battery short 
term, its probably enough of an unneeded drain that I'd just remove it every 
time I drive.

Also measured the draw on the aftermarket Clarion stereo that once drained 
the battery.  Drew about 160mA while off and drained the battery in about 3 
weeks of the car being parked.  That unit is no longer used...for other 
reasons...

At some point in the next little while I'll be changing the car battery. 
Just out of interest, I'll make a point of measuring at the battery, what 
the current draw on the battery is when the car is completely shut down...to 
maintain the clock, and ECU memory, and other things that draw power while 
the car is unused.

Finally, it was the rear-window child lockout that was stopping the rear 
lighter from working.  I'd forgotten about that.

MC
--------------------------------------------------
From: "Huw Powell" <audi at humanspeakers.com>
Sent: Saturday, December 17, 2011 3:21 PM
To: "Mark Rosenkrantz" <speedracer.mark at gmail.com>
Cc: <quattro at audifans.com>
Subject: Re: Cigarette Lighter and USB Adapters

> Just be sure not to leave it "on" when the car is off... quite a few cigar 
> lighters stay on all the time, IIRC.
>
> On 12/17/2011 8:53 AM, Mark Rosenkrantz wrote:
>> 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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