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18v drill battery to 5v regulator?

  1. Jun 12, 2013 #1
    18v drill battery to 5v regulator??

    Hi I have been doing a bit of research but am still a little unsure,
    I am trying to charge an iPhone from a dewalt drill battery,

    What I have so far is that the iPhone is a 5v 1000ma supply
    And the dewalt battery is 18v lithium ion

    Can I use a 7805 regulator or will I have to use a 7812 regulator first?
    Also what heat sinks etc would I need

    Thanks for any help
    Sorry not up on the electronics !! Ha
     
  2. jcsd
  3. Jun 12, 2013 #2

    berkeman

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    Staff: Mentor

    It would be much more efficient (the Dewalt battery will last longer, and you won't need heat sinks) if you use a switching DC-DC buck regulator to convert from 12V to 5V. You may be able to find a pre-built one, or there may be simple electronics kits that you could solder together to do this...
     
  4. Jun 12, 2013 #3

    berkeman

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    Staff: Mentor

  5. Jun 12, 2013 #4
    This regulates the voltage - USB Charger

    Any choice of these is the power supply, ensure it is rated at 7.4v or 2s (3.7*2) - Batteries

    These are the proper plugs for the battery(s), "female" are for the batteries - Plugs/adapters

    Chargers can be had on the cheap too, most are offered without a power supply themselves - Cheap wall charger good for 3000mah (about a 5 hour charging time)

    probably total $40-50 incl shipment to an open trade area for a 3000mah power supply for usb charging....not bad at all. Oh but requires mere guerrilla precision soldering skills.
     
    Last edited: Jun 12, 2013
  6. Jun 13, 2013 #5
    Last edited by a moderator: May 6, 2017
  7. Jun 13, 2013 #6

    berkeman

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    I don't see a datasheet at that page (I may have missed it), so it's not clear how to set the output voltage. I'd stick with a fixed version, like the one I posted. Because cars use 12V batteries, 12V to 5V step-down converters are pretty common.
     
    Last edited by a moderator: May 6, 2017
  8. Jun 13, 2013 #7
    Will this be suitable ?

    http://uk.rs-online.com/mobile/p/switching-regulators/6664379/

    As I am In The uk I have been checking local sites will I need anything else?
    Sorry for the questions
    Thank you in advance
     
    Last edited by a moderator: Jun 13, 2013
  9. Jun 13, 2013 #8

    berkeman

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    That looks like a reasonable candidate. Check the datasheet to see if you need to add external capacitors --they may be included inside though.
     
  10. Jun 13, 2013 #9
    http://www.tracopower.com/products/tsr1.pdf

    According to the data sheet an input capacitor is only needed when input is greater than 32v so hopefully this will be all I need I will order it and let you know how I get on thanks
     
  11. Jun 16, 2013 #10
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