9v display, what battery/regulator to use?

Hi there,

i need some advise for choosing a good battery for my display. My display comes from an old portable dvdplayer. The dvdplayer runs on 12volt.

I took the screen out of the dvdplayer. The screen can run on 7.5volt (probably also on 7.4) but runs better on 9volts and it also works with 12volt.

I tested a normal rechargable 9v battery wich can run for ±30 minutes. [size=85]http://www.amazon.com/Energizer-NH22BP-9-Volt-Rechargeable-Battery/dp/B00000JGN9[/size]

Now, because i want to use the screen for a PiGRRL [size=85]https://learn.adafruit.com/pigrrl-raspberry-pi-gameboy[/size] i want a good rechargable battery that can run for at least one hour.

[size=85]---- Questions ----[/size]
I dont know anything about step-up or step-down regulators, i also dont understand what A stands for in “5 A switch allows for input currents up to 5 A” for example.

What are my options?
Is it possible to attach this battery [size=85]https://www.pololu.com/product/2226[/size] to 9v step-up regulator and how long will it power my screen?

If this is possible how long will this battery work? [size=85]https://www.pololu.com/product/2220[/size]

Or is this just not working at all and do i need to get a bigger battery and use a step-down regulator?

[size=85]---- Recap ----
I need some advise for choosing a good battery for my display.
I want a rechargable battery that can run for at least one hour.
The screen can run on 7.5volt but runs better on 9volts and also works with 12volt.
I tested a normal rechargable 9v battery wich can run for ±30 minutes.


There is a blog post on our web site that discusses the way batteries are rated and the sorts of things that go into determining how long a given battery can power a load. I recommend reading it carefully to better understand what a rating like A (amps) means for an electrical load and how that rating relates to battery life.

Generally there is a range of voltages that electronic components like displays are designed to operate at. Often times, consumer products like a portable DVD player will have different voltage ranges that the various components that have been integrated inside it will require, so they often contain multiple voltage regulators to change a supply voltage to the voltage required by a component or group of components. A voltage regulator like our step-up regulators (which increases the voltage from input to output) or step-down regulators (which decreases the voltage from the input to the output) can be helpful if you have a supply voltage like a battery that is different from the voltage required by a load.

Also, you should be aware that the voltage rating of a battery like a 9V or 12V battery is a nominal rating and that the actual voltage provided can vary by several volts as the battery is charged and discharged. How did you determine the input voltages for your display? If you are only trying batteries with different nominal voltages, I suggest using a multimeter to determine the actual voltage that the battery is supplying to the display to determine where it runs acceptably.

I cannot say which of our regulators or batteries might work for your application with the information you have provided so far. Once you know what voltage you would like to power the display with it should be possible to use a multimeter to determine the amount of electrical current (amps or A) it requires at that voltage. With those numbers, it should be possible to determine if we carry a battery that will power your display for a specified length of time and to determine whether a voltage regulator in your setup might help.


Hi Natan,

Thanks for you reply. At my first post i did just attached a voltage adapter (where i could change the voltage) to the + and - of the screen.

Now i have mesured the actual voltage from the dvd to the screen. Its around 9volts. I also mesured the current its -0.47. I attached some photos with the multimeter outputs.




Since your screen draws about 500mA, you would need to find a 9V battery with a capacity of at least 500mAh if you want it to run for an hour. The highest nominal voltage of battery that we carry is 8.4V, but it sounds like that might be fine for you. Please note that 8.4V is only the nominal voltage, and the actual voltage will be higher when fully charged and lower when discharged.

If you wanted to use a battery with a higher or lower voltage, you would probably want to use a regulator, and then depending on the voltage you want to use the capacity you would need to get an hour of life out of it would change. If you do want to use a different voltage, let me know and I might be able to suggest some regulators or batteries that would work.

- Grant

Hi Grant,

Thanks for your reply.

I would like to use the 8.4v battery, do i need any regulator for it?

If possible i want to recharge the 8.4 battery with a 9v dc power adapter. Do i need any regulator for that too?

I will order it as soon as i know :slight_smile:

- Maurice

From your description, it sounds like your screen might be okay running as long as the voltage is around 9V, in which case using an 8.4V battery without a regulator will probably work for you. As I mentioned, 8.4V is the nominal voltage and fully charged the battery pack can have an actual voltage over 9V. If you want to add a regulator to be on the safe side and make sure the your LCD gets a steady voltage, you could add one like this step-up/step-down voltage regulator to your system.

To charge the battery pack, I recommend using an actual battery charger. We have the iMAX B6AC V2 charger, but there are many chargers you can get to charge NiMH battery packs. Alternatively, you could make your own battery pack using a battery holder and individual AA or AAA size rechargeable batteries.

- Grant

Hi Grant,

thanks again for your reply. I still have one final question before i decide wich battery i am going to use.
Is it possible to connect two regulators on one battery? Check the image for an example

- Maurice

Yes, you can supply power for two regulators off of one battery, like you show in your diagram.

- Grant

Hi Grant or another reader :wink:

i finally found time for my project again and orderd this battery
its 3.7v and draws 6600 mAh.

Now i want to use two step-up regulators to charge my raspberry pi 5v, and my screen 9v (see above).
There are several regulators in the shop ( i can choose step-up or step-up/step-down). Wich regulators in the shop are the best for me? And is my bettery ok to use?

- Maurice

That battery sounds like it will probably be fine. For the regulators, you want to make sure the voltage regulators you choose can supply enough current for the devices you want to power. The efficiency graphs on our regulator product pages can generally be used to get a rough idea of the absolute maximum current the regulator can do for specific input and output voltages. If you want more specific advice, please let me know that input and output voltage you want from each regulator and the current that each will need to do.

- Grant

I want to use the battery for input voltage.
Then this will be the input/outputs:

3.7v to 5v/2A (Raspberry pi 2)
3.7v to 9v/500mA (Screen)

Which regulators are the best to use? Please share the url so i can order :slight_smile:

For the 9V regulator, one of our 9V Step-Up Voltage Regulator U3V50F9 should work, and one of our 5V Step-Up Voltage Regulator U3V50F5 should work for your Raspberry Pi.

- Grant

Hi Grant,

thanks for all your help. I just ordered the regulators. I will share some photos from my project when the Raspberry and LCD Screen are working :smiley:

- Maurice