DC-DC Step Up Converter Advice

[ToPFouraces]

Hey guys, I'm looking to build a raspberry pi laptop, and as part of that I need a way to power the LCD screen.

I have bought one of these DC-DC step up converters: http://hobbycomponents.com/power/698-xl ... -converter.
And I'm trying to power this screen (I believe it requires at least 12V 2A): https://www.amazon.com/Philips-Lp154wx4 ... B003TP4JBO.

I have a powerbank consisting of two 3.7V Li-ion batteries in parallel, which I have used as the input for the step up converter. I have wired up a 5.5mm barrel jack to the output, which plugs into an LCD board to power it.

I have tuned the output of the step up converter to be 12V, 3A. My question is: Is it safe to have 3A instead of the required 2A? Is there anything else I need to place in the circuit to ensure the safety of my LCD screen?

If this is unclear, let me know and I can attach photos

Thanks!

[tyler335]

Few thoughts...

- Can that screen even accept the signal from your raspberry pi (30-pin connector for screen)? I'm doubtful that it will work correctly.

- DC-DC converters tend to run hot. Don't place them by your batteries.

- Size your battery wires to the DC-DC boost converter rather large. If your screen is pulling 12V@2A then your batteries are going to be sending at least 6.5A to the boost converter just to run the screen (that is assuming that your screen is ONLY pulling 2A - Amazon doesn't say; ALSO this doesn't count in any other power draw from your batteries). MAKE SURE YOUR LI-ION BATTERIES CAN SUPPLY THAT CURRENT. Quickly discharging Li-ion batteries is dangerous! I would use a 12V battery and use a DC-DC buck converter for you 3.7V needs. BE CAREFUL!!! Make sure that the batteries have their safety circuits. When Li-ion batteries catch fire, things get nasty quick: https://www.youtube.com/watch?v=AAZ62tUtc0w

- As for power supplies/converters/etc., electrical loads (like your screen, RPi, etc) will only pull the amount of current that they require. You always want your power supply source to be rated higher than what your loads are. If you supply 3A and your loads only pull 2A, then you are fine. Like wise, if your power is rated for 3A and your loads pull 4A, expect lots of trouble and possible fire. (Btw, your DC-DC boost converter is only rated for 2.5A, not 3A.)

- Once again, your set up is a little risky. Be careful!!!

[ShadowFax]

@ToPFouraces, how are you going with the step up converter?
can you run the LCD with powerbank and that converter?

I am currently in the same situation as you, trying to run my 10 inch LCD driver board (RTD2660H) off my powerbank.
Last time I tried to use powerbank that has QC, but I got no luck.
The board is on, its just the screen showing blank.
But when I plug in 12V 1.5A power supply for my tv box, the screen is working.

[ToPFouraces]

Thanks for the reply tyler335. I looked into battery circuit protectors and realised it wouldn't be feasible to get a DC-DC step up converter and circuit protector that could boost 18650s to 12V 2A.

@ShadowFax, I can run the screen with the step up converter, but it is not safe since it exceeds the operating conditions of the step up converter. It will also drain the batteries to a point where they can no longer be charged and used, unless you have a battery protector in your circuit. However, it's not really possible to find these that output a current high enough for what we need.

I would suggest using a powerbank like this: http://www.ebay.com/itm/Multifunction-6 ... SwWxNY2gBW. This is a powerbank for jumpstarting a car. These powerbanks have USB outputs that can power a raspberry pi, etc. They also have a 12V 2A barrel jack output that should be able to power your screen. This is a much safer alternative that I would recommend.

I will be purchasing one soon, so I can let you know how it goes if you'd like.