USB power wiring for Accessories advice
  • Help
Results 1 to 11 of 11
  1. #1
    Fellow Frogger! laurie_lewis's Avatar
    Join Date
    Nov 2010
    Location
    Armidale, NSW
    Posts
    234

    Default USB power wiring for Accessories advice

    Hi all,

    Again showing my ignorance where power involved. I am just doing some planning for running some in car USB powered devices. As they use the USB cable they should all be limited to 5 volts, I believe. What is getting me confused is the Amps and watts and what electronics do.

    Advertisement


    I have seen on e-Bay that you can get adapters with 2 USB outlets that fit into your 12v power socket. 1 being 5 volts @ 1 amp and the other being 5 volts @ 2.1 amps. I am assuming that the amps are the maximum outputs. The next assumption I am making is that a device will only pull the current it needs. So if it is a 5 volt device that needs 500 milliamperes, will work fine on either plug - just pulling what it needs. If you put a device that can pull 5 volts @ 2amps (ipad) on the 2 amp plug, it will charge fine (10 W). It will also charge on the 5 volt @ 1 amp plug just taking twice as long to charge.

    Apple pretty clearly states this for all it's products but once you step outside Apple I am unsure. I have a GPS that is USB powered. All I can find on it is it telling me a maximum of 5 watts. Now does that mean you only plug it into the 5v @ 1 amp plug or can It be used on the 5v @ 2 amp plug as it will only pull 5w as that is all it needs? My daughters phone is a Nokia so can I use it on either plug or am I restricted to 5volts @ 1amp to ensure the safety of these devices.

    Thanks

    Laurie

  2. #2
    Banned
    Join Date
    Nov 2004
    Location
    sydney, australia
    Posts
    11,301

    Default

    *yes, the current levels noted are the maximum the USB adapters can put out.

    *yes, a device will only draw the current it needs

    *no, you shouldnt plug an iPad into a 1amp adapter. the problem is that the iPad will try to draw 2A through the adapter and (roughly speaking) one of two things will happen: it will be overloaded and overheat with potential damage, or it will cut out due to internal protection, and not charge at all. that is, for example, what happens when i plug my iPhone into a cheap 240v adapter at home. sometimes overloaded adapters will cycle between On and Off repeatedly, due to the internal protection cutting them off, then switching back on.

    *yes, you can plug your GPS into either. as long as the adapter has a maximum output at least as high as the requirements of the device, then you can plug the device in. as you correctly already assumed, the device draws current from supply, and the supply does not 'force' current through a device. that is why you can plug you iPhone charger at home into the wall socket, which is itself capable of supplying vastly more power than the charger uses.

  3. #3
    Fellow Frogger! laurie_lewis's Avatar
    Join Date
    Nov 2010
    Location
    Armidale, NSW
    Posts
    234

    Default

    Thank you Alexander. I can now continue with a bit more confidence..

  4. #4
    1000+ Posts Greg C's Avatar
    Join Date
    Oct 2003
    Location
    Sydney
    Posts
    1,304

    Default

    There is a unit you can get from most phone shops that has a USB port on it. Great thing, it is small enough to fit in a Xantia cig lighter
    Mine

    CX Prestige
    Toyota Prius

    In the family

    Xantia SX

  5. #5
    Fellow Frogger! laurie_lewis's Avatar
    Join Date
    Nov 2010
    Location
    Armidale, NSW
    Posts
    234

    Default

    Yes Greg, I have one and I am about to buy some more from eBay. The only problems I have found with the one I have is that it can cause a bit of interference with the radio when in use. The ones I was thinking of using are dual ports. 1amp and 2 amp. Test all the wiring and cables for interference before installing. Hoping better quality cables with shielding might stop any interference.

    Laurie

  6. #6
    1000+ Posts Greg C's Avatar
    Join Date
    Oct 2003
    Location
    Sydney
    Posts
    1,304

    Default

    Mine is an ROHS Mini USB Charger. Output is 5Volt 1 amp. They work perfectly in a Xantia and a Prius. No interference but then I only listen to FM on the radio
    Mine

    CX Prestige
    Toyota Prius

    In the family

    Xantia SX

  7. #7
    Fellow Frogger! flipperman's Avatar
    Join Date
    Oct 2012
    Location
    Melbourne, Victoria, Australia.
    Posts
    417

    Default

    I run a cig into 3 female adapter then i have three usb adapters in that running 2 phones and a gps full time 8-10 hours a day and they all keep charged in my triton.

    I have a cig to usb adapter in the BX charging my phone which i use to stream to my sony stereo.

    If you get a usb power cord (eg: a blackberry one) most phones with the cord can also be charged though the usb on the car stereo. I don't do it this way in the BX as the radio is close to the gear lever and i don't want the cord there, this way charges my android phone but not my wndows 8 mobile.
    CitroŽn's that own me

    - 2008 C5 X7 Tourer (Estate) 2.7 DoubleTurbo Diesel UHZJ - V6.

    CitroŽn's that formally owned me

    - 1990 BX TRI Estate Manual. .. . "Phoenix" - "Donated to Science"
    - 1990 BX TRI Estate Auto. (Traded In)
    - 1987 BX TRI Hatch.

    -------------------------------------------------------------
    Australian Citroen BX - All about the Citroen BX in Oz
    -------------------------------------------------------------

  8. #8
    Fellow Frogger!
    Join Date
    Nov 2010
    Location
    Lavers Hill
    Posts
    321

    Default

    I have one of these gadgets and I'm pretty convinced that the wording on the packaging is confusing.

    (ASSUMING THAT THE GADGET I HAVE IS EXACTLY THE SAME AS THE ONE YOU HAVE)

    The packaging says some thing unclear like "socket 1 - 2 Amps. Socket 2 - 1 amp." The sockets are labelled A and B.

    I reckon it's pretty unlikely that they'd have two different circuits with two current levels. (current = amps.) I think it is just written in clumsy English.

    I think what they REALLY mean is: you can use one socket (either one), and it will supply up to two amps. If you use both sockets, then they can only supply 1 amp each. (total output is still 2 amps max.)

    Ours is regularly used to recharge an Ipad and it can recharge it fine from either socket. I have another similar gadget with only one USB socket, it is 1 amp max and it is extremely slow to recharge the ipad, though it can do a phone no problem. If you use the ipad while it is charging, it recharges slower with the 2 amp charger and the 1 amp charger can't keep up - the battery charge still decreases if you try to keep using it on the 1 amp charger. (which is of course why we upgraded to the 2 amp unit.)

  9. #9
    Fellow Frogger! laurie_lewis's Avatar
    Join Date
    Nov 2010
    Location
    Armidale, NSW
    Posts
    234

    Default

    The one I am currently using says 3.1 amps and shows which plug is for phones v ipad. That was why I was checking if it was safe to plug a 5W device into the supposedly 2.1 amp socket. Didn't want to fry anything. It would be interesting to pull one apart and see If two circuits or one.

  10. #10
    1000+ Posts Greg C's Avatar
    Join Date
    Oct 2003
    Location
    Sydney
    Posts
    1,304

    Default

    You won't fry any device. The charging current is controlled by the device. All it wants is 5 volts and it will look after the rest. Obviously if you don't supply the current the device wants, it will charge slowly, or not at all as has been mentioned.
    Mine

    CX Prestige
    Toyota Prius

    In the family

    Xantia SX

  11. #11
    Fellow Frogger! laurie_lewis's Avatar
    Join Date
    Nov 2010
    Location
    Armidale, NSW
    Posts
    234

    Default

    Greg that is what I thought but this is not a situation where you go ahead and seek forgiveness after if wrong, it comes out of my pocket. :-)

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •