I have a 3.5 inch LCD that I would like to power with a battery pack. Since I know precisely squat about electricity I would like to get suggestions and recommendations.

I would like to use AA batteries, and since I need 12 volts of power, I would need 8 of them, right?

The only thing I'm worried about is that fresh AA's sometimes start out with more than 1.5 volts and I don't want to over-power the LCD and damage it. Does the controller take care of regulating the power that makes it to the LCD?

Any pointers?


Tgreenwood

If you have the original power supply for it ,you could measure the output from it.
If it is regulated it will be at 12 volts but if its not regulated the voltage will be higher and you can safely use up to that voltage .
Most electronics will tolerate small variations and still operate properly
If it was made for automotive use it probably will be good to about 14 volts..

All household electronics are made to be used in many different power quality settings.

If your 12 volt adapter puts out 12 volts when your power is 120 volts during the day then it will only put out 11 volts when your power is 110 volts or less in the evening. Rural power (at least in Canada) is often well over 120 volts hovering around 130 volts. So a transformer there would put out 13 volts.

So there shouldn't be too much risk in going a volt or two over. (Of course i don't know the tolerances for this specific LCD so be vigilant.)

You will want to use a multimeter in series with the DC side (not the wall side!) of the 12 volt transformer and find out what how many mA (millamps) it pulls.

Most batteries are rated for 1800 mAh (mA hours).

So hypothetically if your LCD draws 500 mA, then 8 batteries in series would run for about 3 hours.

However the voltage also drops exponentially over time with use. So you could maybe expect to gain 2 hours time from the LCD.

There for if you were to connect 16 batteries. Parallel in pairs, and then put the pairs in series, hypothetically you could get 4 hours of LCD.

I would recommend using a car battery personally Then you would get 100,000 milliamp. And you don't have to put anything in series. And it would last for about... *math in head* 53 years.

I would recommend going to a hobby store and asking someone there about batteries used in model planes. Usually those batteries are rechargeable, and come in 1.5, 6, and 12 volt configurations. And have a special charger to go with them.

Of course this is all hypothetical and someone more experienced in battery literature (i'm a commercial electrician) might know more.

But that should be the general idea.

Almost all smal Lcds have a pretty wide electrical range.

I work with a lot of 2.5"-7" Lcds to make portables. And most can be run anywhere from 7.5v - 12v.

It's best to underpower them slightly than to overpower them. I would say to run it at 9v and it should work fine.

And be sure to use good rechargeables to get the best results.

Excellent advice!

It didn't come with a power supply/adapter/wall wart, all I know is it takes 12 volts. So, I can't check what the output should be.

I'll try the 7.5 volts first with AA batteries and see how it goes.

Thanks!

Tgreenwood

Well I have a portable 7" LCD in my car that is hard wired to the 12V system. When the car is running, the power systems is about 14.4V. When off and electronics running for a bit, it can drop to about 11V. I even had the LCD working when watching a movie in my car with the car off, and sub running full blast. The car got to around 9.8V and everything worked fine. Now the car took some time starting, but the LCD did fine. I'm kinda doing the same thing you are. I have a 160Gb media HD play i bought off ebay, and I'm looking at getting another 7" screen. I want to kinda make an IPOD video, but with ALOT more storage, and 7" LCD. I'm looking at Lithium Ion batts right now, but Li-Ions are not something you just plug and play.