17' tablet (OPi normal)

KingNyx

You can raise that run time by figuring out ways to dim the screen, and turning the pi's futures off that you don't need. In the end we are pretty much jsut working with theory

gaara

I will see the result, and I remove some features if the working time is too low...
In theory with 42000 mAh@12V, It can run 4h without the sata drive, and without sound. So 2h is a good estimation, I hope !

KingNyx

Hopefully Your first battery in my opinion probably had some poor form of voltage conversion.

Because 42AH x 12V should be 504WH. Thats a lot of watts. If your pushing 30 watts that's a 50% efficiency which is garbage. You'd still be pushing 16 hours. at 22 watts you'd be pushing 22 hours.

Because those first times worked on that battery but im pretty sure it has conversion issues. Thus the extremely low run times. Your battery will be natively 12volts so you should see a higher efficiency.

gaara

Yes, my actual battery is a little tired, I have used it with a solar panel every day during 6 months (for a trip).
If this tablet is 16 hours working time, I file a patent now, and open a kickstarter !!
No, I don't think 16, even 10 hours should be possible. But it's permitted to dream XD

Pending the battery, the sata drive will coming faster, next week I think. So I could have a best idea of the consomption (and modify the code to boot with it)...
However, I will write a report of all my tests, when I have received the material. (some weeks for the battery, I'm living in France)

KingNyx

Unless im doing my math right that should be correct.

42,000 Mah = 42Ah

A x V = W
42A x 12v = 504W

22-25W per hour means it will be several hours of run time.

gaara

If this is the case, I could put better speakers.
I could also set the voltage to 14V, to have a better luminosity (it's an old screen, 2006 I think, so it's not the same as a IPS screen)
But 42Ah is also a theory, if I reduce 20%, it's 33.6Ah. And so 16 working hours !!
I will see, because there's always bad surprises...

KingNyx

Yah, you'll have to wait till you finish the real world tests to find out. It'll be cool to find out.

What is the battery you are using btw?

This is the one I plan to use... But its no where near the capacity of yours. http://www.aliexpress.com/snapsh ... erId=66155330191238

EDIT: http://www.alibaba.com/product-d ... mAh_1454289280.html

If that is the one you picked, the 30,000 mah is for the 5v socket on it. Not the 19 volt socket.  

The other technician was in today and he agreed that I calculated run time correctly. But only if the mah was correct, and like we thought they listed it for the 5V not @ 12V.

So its actually 150WH meaning itll run 22-25w for 6-7 hours if its not lieing about its capactity.

gaara

I take this one: http://www.aliexpress.com/item/4 ... es/32295702252.html
It seems the same as your link, but I don't know if inside is the same...

6-7 hours is like a normal -new- laptop, and decrease with time (mine is 2h now, 2011 asus laptop 6 cells)
So it should be a normal time even if it's 150Wh. I just want 2~3h. After, it's bonus time.
In fact I take the biggest one, with slim profile. I've seen others @50Ah, but they can delivery only 5V. This one is 12~19V (verified! :p).

And alibaba.com don't sell at individuals persons, only for professionnals. That's why the price is not displayed.
Only aliexpress can sell to us.

For your project, you can use a smalest one, because your screen is 7' if I remember!
In fact, screens are very gluttons of power, and CPUs pump nothing comparatively !

KingNyx

Indeed But I prefer long battery life. I will be using mine to watch anime while I wait for radio programming and firmware updates to finish when i'm out in the field. Plus the power goes out VERY often here. At least once a month for a day or two.

Youll still get good run time. But ALWAYS assume they match the Mah to the lowest Voltage. When they say 42,000 mah they mean for the 5volt usb on it. The milli-amp rating just says how many amps it can put out for an hour at a specific voltage. That number will drop as you go towards 19v.

so at 19 volts which it specifies it'll actually be 11,000mah. Or 210WH. Which is still excellent. Its just a cheap marketing trick.

gaara

On my laptop, it's a 11.25V@5600mAh battery (13' screen) The Asus screen board is optimized for 13' but the board I have bought is not really optimized I suppose...

Your battery is 12V@9800 mAh, but how have you found 11.000mAh for 19V ? Can we know for 12V ?