# I have 7 inch screen which takes 12V/2A, is there some way to make it run with 5V/2.1A?

So I'm making a portable raspberry pi system, with ( http://www.ebay.com/itm/7-Inch-TFT-LCD-Monitor-Touch-Screen-Driver-Board-HDMI-VGA-For-Raspberry-Pi-B-/281462562765?pt=LH_DefaultDomain_0&hash=item418879dfcd )(not this but same style) screen, and I have a portable battery pack with 5V/1A and 2.1A outputs. I know that Rpi needs 5V/1A but is there a way to make the screen work with the 5V/2.1A?

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steveastrouk3 years ago

You need 12V @2A = 24W to run the screen. a 5V 2A supply is 10W. No, you cannae beat the laws of physics.....

TrraZZy (author)  steveastrouk3 years ago

Any idea where I could get that kind of rechargeable battery, what lasts long too?

3 years ago

How long do you want to go ? A Sealed Lead-Acid battery is 12V out of the box, and a 50Ah battery isn't terribly big.

TrraZZy (author)  steveastrouk3 years ago

That sounds pretty good, but how big it would be? Because my case is only 200x120x75mm.. and pi, screen's board and other stuff what is going inside the case takes some of the space

Vyger3 years ago

Use 2 battery packs for the screen.

TrraZZy (author)  Vyger3 years ago

You mean two 5V/2.1A or 1A?

3 years ago

Hooked in series it would give you double the voltage. It's probably a little more than 5 so you would end up with a little less than 12. It may or may not be enough depending on what the tolerances are.

But if you really want to go with batteries a 12 volt LI battery from a cordless drill would give you everything you need. !2 volts with lots of amps and a handy charger on top of it.

mpilchfamily3 years ago

The screen will not operate at lover then specified power. What you need to do is use a 12V input for the whole system. Take a lead from the 12V input, run it through a 7805 voltage regulator to give you the 5V needed by the Pi and your all set.

TrraZZy (author)  mpilchfamily3 years ago

Will it work with 12V/1A? Or do I need the 2A?

3 years ago

If it's rated for 2A then it needs 2A. Devices don't over state their power ratings. They need what they need. The driver chip for the screen may be able to operate within a range of voltages but it's not the thing hogging all the power. It's the screen and backlighting that need the power.