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Car phone connector to powerpoint

Discussion in 'Troubleshooting and Repair' started by dlbtiger, Aug 7, 2013.

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  1. dlbtiger


    Aug 7, 2013
    I have a car phone connector with several contacts in my armrest I would like to convert to a powerpoint for charging another phone or device. I was thinking of just cutting the cord, finding the 2 - 12V wires, taping the others, and finding a powerpoint part to wire in.

    Is this reasonable, and where might I find the powerpoint part?

  2. GreenGiant


    Feb 9, 2012
    Im not sure if that will have enough current supply for it to work well.
    Also before you cut it make sure that it has 12V on it.

    Either way if you are dead set on using it and cut it, I would say regulate it down to 5V and use USB female connector, that way its almost universal, just need to find the right USB cabe for your phone/device
  3. dlbtiger


    Aug 7, 2013
    That's sounds good. What parts would I need to accomplish this.

    This a factory installed (2000 Mercedes) phone cord that charged the phone and used the car sound system. I would just like to keep my current phone charged.

    Thanks again.
  4. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    Nov 28, 2011
    Many modern phones use MicroUSB connectors can be charged from a USB connector. Is that what you want? If so, you will need a regulator to drop the automotive battery voltage down to 5V, which is the standard USB port power rail voltage.

    Since cellphones can draw up to 1A when charging from USB, you will need a regulator that can supply 1A, or 2A if you want to charge two phones simultaneously. This regulator will need to dissipate significant power, because it is dropping 7~9V at 1~2A. For this reason, you should use a switching regulator, which is much more efficient than a simple linear regulator.

    You also need to consider an issue known as automotive load dump - see Usually, regulators for automotive use are rated for up to 70~80V input voltage, to handle this problem.

    It's also possible to use a surge suppression device such as a varistor to limit the voltage coming into the regulator during load dump.

    Maxim make two nice looking switching regulator ICs that would be suitable, but you would have to build up a circuit board. Alternatively, you could try to find preassembled power supply boards on eBay that use these ICs, or that at least have a high maximum input voltage limit. The Maxim ICs are MAX5035 (1A output current, see and MAX5090 (2A output current, see

    You could use a module like this one:
    ... but you should add a varistor across the input to protect it from load dump. Something like this:

    Edit: You'll also need a USB type A receptacle. See and use the filter columns.
    Last edited: Aug 8, 2013
  5. dlbtiger


    Aug 7, 2013
    Exactly the info I needed. I used to design, etch, and build circuit boards in the early 70's (yeh I'm an old man) but I no longer have the equipment or inclination to make a circuit board. The module route is for me.

    Thanks for all the help!
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