How to power an old laptop screen with an old laptop battery ?

Hello instructors,

I'm currently playing with Rasberry pis, and I just started a new project.
I found information showing how to re-use the screen of a dead laptop via a controler board you can find on eBay.
I'm planning to integrate all this in a suitcase to create a mobile retro gaming console. It should be easy to add a simple 220V plug to power all this.
But I was just thinking it could also be nice to be able to use this on battery as I also have many laptop batteries @home.
Rasberry power input is about 5V 3A
Audio amp input is from 1.8V to 12V
Screen controller board is 12V 4A

Here is what I want to do :
> When plugged : Add a circuit to charge the battery via a 220V input. That circuit should also convert the 220V to the power needed for the Pi, the audio amp  and the screen.
> Unplugged : Add a circuit to convert the battery output to the power needed for the Pi, the audio amp and the screen.

I have no idea where and what to search for. Should I reuse the laptop power unit ? Any help would be highly appreciated.
Please excuse my English mistakes. This is not my mother tongue.

Downunder35m3 months ago

4A for a screen controller seems to be really excessive.
An old laptop would not be able to provide that power.
To make it run on batteries do yourself a favour and have a running system on "normal" power so you can take accurate measurements about the real power requirements.
From there first start to check what is available in battery options for this power.
Consider using a battery system with more than 12V, like 18 or so.
This way you have reserves and can use step down converters or simple power regulators like the LM series.
You might find that with the currently stated requirements the batteries you need might either blow the budget or the weight/size limit.

bbielecki (author)  Downunder35m3 months ago

Thx for your answer. That's a lot of information for my basic knowledge. Here is the board I bougt :

It's recomanded to be used with a 12V 4A power unit, and it's what I used when testing. It's working fine. You mean I should be able to power this with less than the recommanded power ?

If you check other (electronic) devices they often rate the recommended power supply far higher that what the device really uses.
Apart from a bit of overkill it is actually common practice.
Let's say your board would be really only using 2A at max and you use a 2A power supply.
In this case the power supply would be always at the limit and quickly overheat.
A 4A supply will not even get much above room temp...

But for battery use the first thing you really need to know is how much power everything actually uses as otherwise you won't be able to calculate how big the battery needs to be - in terms of amepere hours (AH).

bbielecki (author)  Downunder35m3 months ago

Thank you again for your precious knowledge sharing.

If I use a multimeter to mesure voltage and amp directly on the plug when screen is powered on and plugged to the raspberry, will these mesures give me a good indication of what I need as a battery power ?