Cigarette Lighter and USB Adapters

[Huw Powell]

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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