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Need 12v in a portable system, how should i approach this?

Discussion in 'General Electronics Discussion' started by Nerdydude101, Jul 30, 2014.

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  1. Nerdydude101

    Nerdydude101

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    Jul 28, 2014
    So the two things that i need to power (mainly) are a raspberry pi (5v) and a lcd screen (12v). The raspberry pi is easy enough to power, it needs 5v 2A and that doesn't seem to be a problem, my issue come in with the LCD screen, my project is supposed to be portable, its a portable media center, similar to a portable dvd player that lets you watch dvd's wherever you are and is run off battery. I want this to be similar, but i don't know how i should proceed in powering the screen, 12v batteries are like are like car batteries (most literally are car batteries from what i can find) and that is a bit too big to be put into something like this, is there a way to step up voltage like they do in some ics? (i have whats called a minty boost that has an ic that takes anything below 5v and outputs a solid 5v) or should i be trying to put some battery packs in series (i was told this is a bad idea but i figured i would just put it out there anyways) or what should i do? any ideas are helpful, thanks!
     
  2. Gryd3

    Gryd3

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    Jun 25, 2014
    You have told us the Raspberry Pi runs on 5V 2A, but have only told us that the display is 12V... how many Amps are required?
    This could alter the proposed solution to how you power the device.

    The item you are thinking of would be a 'boost converter', which can take a lower voltage and provide you with 12V.
    Please keep in mind that converting is not free, and that losses in conversions will affect battery life. (Please also note that the Pi by itself will draw much less current than 2A. I have successfully ran a Model B Pi on a 700mA source for the last month and a half. Model A will require even less, but I do not have info on the B+ model...)
     
  3. Nerdydude101

    Nerdydude101

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    Jul 28, 2014
    The screen will take 2A as well, i will probably be using the model B+ but all that is going to be plugged in is the screen (which needs to be powered by something else, so it will just be sending a video signal), 3 flash drives, and a dongle to attach a keyboard (the keyboard that i like uses AA batteries and has a very long life so I'm not worried about trying to power that off of the overall battery system). Here is the info from element14 on the b+: "600mA up to 1.8A @ 5V" thanks for your help again.
     
  4. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    Nov 28, 2011
    I guess I would use a battery of Li-ion or Li-pol cells to provide 12V and step it down to 5V with a buck regulator. Check the input voltage range of your screen though; if it's narrow, you might need to use more cells and another buck regulator to step the higher voltage down to 12V.
     
  5. shumifan50

    shumifan50

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    Jan 16, 2014
    How long do you expect a charge to last: 10 mins or 10 hours; this also affects the solution. But I agree with Kris, it sounds like a LiPo battery is the way to go.
     
  6. Nerdydude101

    Nerdydude101

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    Jul 28, 2014
    Preferably I would like it to last ~2hrs, but the longer, the better, do you have any LiPo batteries you would recommend? I see most of them are ~1600mAh, so isn't possible to hook them up in parallel to get more runtime?
     
  7. shumifan50

    shumifan50

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    Jan 16, 2014
    You can get them up to just about any rating you want. I have some 4000maH ones. They just start getting big and not too mobile.
     
  8. Nerdydude101

    Nerdydude101

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    Jul 28, 2014
    Would 2 of these in parallel work for the ~2 hours and getting the proper voltage, I'm pretty sure but if you know of a better battery for around this price please tell me: http://www.amazon.com/gp/aw/d/B0027...qid=1406735977&sr=8-34&pi=AC_SX110_SY165_QL70
     
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