Convert A/C to Battery Pack?

Ok here is what i wanna do, and your all gonna think I am crazy, but this is mostly for my little girl.  I want to take a very cheap dvd player and another cheap video screen, (the kind you find for the back of auto head rests) and glue them together, make a battery pack, and wire the two together to the pack and, the point is I have the devices and they both are rather low energy draw devices, so i just need to know if I can make a battery pack or perhapse a radioshack project battery holder and how many batts I would need etc.. I will admit the math is a bit confusing for me. but here it is, the dvd player is rated as AC 120 v, and it says it has a draw of 10w, which if I am not mistaken is very low drain and awesome for an ac device.  the monitor is DC with an adapter but can also have an optional car adapter (which I don't have, but I would just use the transformer's cord/jack to wire it in.)  The back of the monitor says it's DC output is 1.2A and again 12v and the transformer itself says it's input is 24w.  So if my math is right, I am looking to make a battery supply to support a total of 34 watts and then I will use both cords to wire them parallel to a battery pack that I need to make, so where I need the help is what kind of a batt pack do I need to make or is it even possible? 

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The DVD player itself uses Mains power to run it but inside is an AC to DC converter. So open up the player and find the power supply inside. If the power supply doesn't have any voltages labeled on the board then use a DMM to measure the output voltages. Chances are the player uses 12V and 5V DC. So you should be able to strip out the power supply and replace it with a good sized 12V battery to run the thing. If 5V and 3.3V is offered by the original power supply then you will need a couple of voltage regulators to get the voltages you need.

There is no need to go through the inefficient steps of converting 12VDC to 120VAC only to have the DVD's power supply take it back to 12VDC again.

Most DVD players i've pulled apart use a PC Molex connector to power the DVD drive. Some even had an IDE cable to connect the drive to the main board of the player. So open up the player and see what you have.

If both items will only need 34 watts @ 12V then your only going to pull 2.8A from the battery. Make sure you get a large enough battery that can support that much output for the time period you want.
It's nice when two tech types come within a watt of each other,
I came in at 35 Watts :-)
iceng5 years ago
You are describing a DVD player, less the $150 new.

blackmagickfox (author)  iceng5 years ago
Both the dvd player and the monitor are old and before I trash 'em I wanna make a project outta em' They were both cheap items, the dvd player itself was something like $45, But more importainly, I am wondering if I can make a battery pack that will support 2 devices in line that pull 34 watts total. Sorry, I was not sure I understood your question/answer.
  • DVD player 120VAC 10W = .084A = 84ma ac
  • MONITOR 12VDC 1.2ADC = 14.4 Watts
  • And you want to run both off of a 12vdc battery
  1. You will need a small inverter to convert 12vdc to 120vac
  2. inverters at low power are only 50% efficient 20  Watt
  3. And the monitor uses the battery 15 Watt
  4. A sealed Lead Acid battery will do 2.9 amps per hr
  5. say a dvd runs 4 hr you need a 12 AMP-HR Battery.