17' tablet (OPi normal)

KingNyx

Nice! Good results! I only knew that one from experience. I've had screens say 5-12V when they wont turn on before 9V. The other issue could be the amps the battery can put off. So it could work on a higher amp rated battery.

Getting a battery pack and cutting it open is an excellent idea since the charging circuit is super important on a lithium battery that changes amperage as it fills up.
The fact that upping the voltage from 9-12 barely brought the amperage down kind of bothers me. You could probably get some resisters and drop the amperage down a bit before the screen. Which should prolong battery life.

Im guessing they have a switching power supply inside the battery and its using extra juice to get it up too 12V and thats also where some of the power is going. But the screen taking the same amperage at a different voltage could be changed since obviously itll run off 9watts. So you could put a resister in and get it down and it should still turn on.

KingNyx

Also keep in mind many batteries lie about their MAH. So always be prepared for 5-10% less run time than you originally planned on getting.

You might consider doing some circuitry and programming to get a battery percentage running inside the tablet too.

gaara

Yes, It's a little complex.
I think 5V and 7.5V doesn't work because the amperage of the battery is too low. But the screen is more luminous with 12V or 14V, so I think I will power with 12V.
The problem of these battery is.. the price ! 100$ for a 30000mAh@12V... So I must be sure before by it :p
But I havn't choice because there's the integrated circuit (protection charge/discharge, balance between cells etc) and the charger. If I buy all separetly, the price will be the same. And more difficult to build.

You say that I can try to add a resistor to decrease the amperage, and so prolong the battery life? why not, but the voltage will be the same? (I'm zero in electronic)
And the screen needs about 0.9A, so if I add a resistor, it will pump more of Ampers from the battery, no ?

I havn't understood your second explaination, and the second resistor.

For the mAh, yes it's always theory... That's why if I'm not sure to do it really. I maybe forgot the battery system, and build the tablet just with a sector power. (100$: I must think before buy!)
And for the program part, that should be great, I have just seen a driver in the kernel to do that. But I don't know how it works, and what is the detector to use it.

KingNyx

Honestly the only thing you can do to make sure the MAH is high enough is to buy one with 5~10% more mah than you actually want. Then you get either more or equal to what you actually wanted.

What I mean with the resister is that your screen needs about 9-11 watts. But even when you raise the wattage it keeps using roughly the same electricity or even more, dropping the amount of time you can run it off that battery for. A resister makes it so only so much amperage or voltage (depends on the resister) can get through. By limiting it too 0.7 amps at 12 volts, instead of 0.85 amps, you'll be able to increase your overall run time. It would be roughly 20% more efficiency as far as the screen goes.

KingNyx

When I get a development card I plan to use a breadboard with some resisters and diodes to wire out a mathematical algorithm. That way the circuit would work in ten segments and when wired to the battery tell me how much juice is left and relay it too the correct pins based on the number.

But right now its theory, but Ill share it once I start my project.

gaara

Ok, so if I have understood I must try differents resistors to see the limit I can put, until the screen shout down. This for juice economy.
For example, I start with 0.9A, then 0.85A, 0.8A etc.. and I see how much I can go. But I think I need also try with playing a movie, because I think the screen pump more of juice in that case (not sure, I will try tomorrow)
I must also think about the sound... that's pump also a lot of juice

I wait for your project to explain me the use of diodes (lightened I suppose?)
If you can write a sheme, it could be great!

Thanks for your explanations

KingNyx

Exactly!
I dont mind explaining it out, thankfully I can edit and add more detail if you need. Being able to ask questions make it a lot easier.

Generally with screens its the refresh rate and backlight that take up the juice. The screen is always refreshing at 60hz. So playing a movie wont make any difference, just uses more power on the PI's GPU. (As far as my electronics knowledge goes anyways)

Sound doesnt use all that much. You can make a radio that has headphones without any batteries. Just using the radio waves. many headphones can run off a 300mah battery for 10+ hours. It jsut depends on the speakers themselves. More volume means more power. Also the sensitivities of the speakers effects it. Less bass makes it easier on the battery. Low tones take a lot more juice.

Shipping from china to me is about a month, so it'll take some time to wait on my project to be able to start. My screen is here and im waiting on the battery, so once it gets here I can help you with figuring out how to make that screen more efficient.

gaara

All right, your help will be very appreciate !

About the sound, I have seen theses speakers. Maybe 2x4W is too much, my choice was for a sound quality. If you can say me if it can be adapted, or if 2x2W is better.
Anyway, I'll purchase the speaker (+DAC maybe, if need) at the end of the build, when all the others things will be ok.
For the moment, the most important is the screen and the battery. 30.000 mAh is the minimum, I would like to balance power and thikness.

Have you purchassed the Orange Pi Plus ? I have the normal model.

For the SATA I have seen this today: adaptater m-SATA and 60 Gb SSD. It's the smaller solution (and faster) I have seen for the moment. The consomption is only 2W.

KingNyx

You want this: http://www.aliexpress.com/item/H ... or/32284124158.html
You just need a cable with two Dc power cables like I just showed, if you used the other thing their it would require a pci-e port which the Orange pi doesn't have.

I wouldn't bother with that SSD either. http://www.aliexpress.com/item/O ... or/32290597355.html Go for this and just take the four screws off to get it out of the casing.

Im (hoping to be) getting the Orange pi plus. Because thickness isn't a problem for me so I can get the battery required to run it as long as I need.

AS for the speakers. Your hardware right now will be around 22 watts if you add in loss of efficiency. So keep that in mind. Adding 8 watts worth of speakers will push you towards 50% more battery usage.

This is quieter but has more bass: http://www.aliexpress.com/item/N ... 5mm/2043370442.html

This is louder but more like a tweeter: http://www.aliexpress.com/item/U ... tts/1323886603.html

gaara

Yes, I already have the SATA cable.
For the SSD, my link was a SATA->mSATA adapter, but finally I found a Sandisk X110 64Gb on eBay, cheaper. I won a bid: 27+4€
This question is solved
For the speakers, 1.5W or 1W is the maximum, I will take this, you're probably right. Do you think I can plug them directly on the Jack output, or need a little amplifier to hear something?
Today or tomorrow if I have time, i will make some try with another ssd (64gb) to see the duration of my little battery. But I must make a backup before, it's my old laptop ssd...

Argg.. boring chapka