My Pi 2 test is running now.
I would do a video but it is a little boring - "on.. still on.. still on.."
The Pi 2 is connected to a Pi Sense hat. When it runs out I will remove the hat and do a second test to compare them.

I did some tests the beginning of the year, unfortunately E14 seams a little difficult for members to search so we seem to be doomed to repeating our selves

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RE: USB POWER BANK // PORTABLE POWER SUPPLY RE: Raspberry Pi Zero - portable power source? Beginner's question RE: What battery to use for portable RPi? Raspberry Pi LIPO battery Pack Endurance Test

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With a Raspberry Pi 2, nothing plugged in apart from a PI Sense hat I got an uptime of almost 7 hours using a power bank. Pretty impressive and way longer than I expected.

00:18:16 up  6:53,  0 users,  load average: 0.00, 0.01, 0.05

The power bank specs:

5v/1000 mA

2200mAh 8.14WH

I had the LEDs running on the PiSense hat constantly.

If it can last 7 hours with the PiSense on a Pi 2 I would expect much longer on a basic Pi with no connections.

cat sense_test.py 
colour = (95, 95, 0)
background = (0,0, 63)
from datetime import datetime
import time
from sense_hat import SenseHat
import subprocess
sense = SenseHat()
while 1:
     #d = datetime.time(datetime.now()).strftime('%H:%M')
     d = subprocess.Popen("uptime", shell=True, stdout=subprocess.PIPE).stdout.read()
     print(d)
     f = open('uptime.txt','a')
     f.write(d) # python will convert \n to os.linesep
     f.write('\n')
     f.close() # you can omit in most cases as the destructor will call it
     d = subprocess.Popen("sync", shell=True, stdout=subprocess.PIPE).stdout.read()
     sense.show_message(d, 0.1, colour, background)
     time.sleep(60)

Greg Fenton how many ampere does it output? correct me if Im wrong please, any powerbank no matter how much mAH and A is labeled can power up the stock pi2 without any board attachment, and without overclocking the pi2 for the first time its booted with the powerbank

im thinking of a powerbank visually that is less thick, almost the same height and width with the case from a top view..would be awesome..compact looking

The power bank specs:

5v/1000 mA

2200mAh 8.14WH

So 1 amp.

Do a google search for powerbank 2200mah and you will see ones like mine.

That "1A" spec means that it should be able to power a raspberry pi.

The 2200mAh spec means that if your pi draws around 400mA, it will run for about 2200 mAh/400mA = 5.5 h.

Now this is slightly wrong, because the marketing guys at the companies making these things found a way to make their numbers look bigger than those of the competition (for a few miliseconds before the others started doing the same).

They don't specify the mAh at the output, but they specify the mAh of the battery inside. So that battery inside will have an average voltage of about 3.7V and with 2200mAh, you get 2200mAh * 3.7V = 8.14Wh.  If the output is at 5.0V, the device will be able to provide that same 8.14Wh minus losses at the output. or 1630 mAh at 5V (minus losses). Generally speaking the losses will be on the order of 10-20%, so you'll get about 1300mAh or 6.5Wh out of such a battery.

(Just calculating this through in the hopes that you guys will be able to do that on your own with your own numbers with this as a guide...)

Greg, will a 2600mAh 0.8A boot my pi2mB?

Roger, yeah the calculation is similar from the vid’s URL I posted since youre the 2^nd person who said this, now I know how to calculate mAH over current. Thanx roger

Check this out guys, making me even worry

http://professional--information.blogspot.com/2014/10/running-raspberry-pi-on-batteries.html

pi1 not model B has a voltage regulator and theres one capacitor compared to pi2mB it evolved to a mobile technology,no?

Similar to roger’s board ehe..

Haha sorry if I seem boring and stuff im still new with this raspberry pi

Hey you two have the same power bank and from the image roger posted it is not connected  to the micro usb.

0.8A should be enough to boot your 'pi. However if the guys who sold you that power bank like to exaggerate, the power bank may sag at currents below 0.8A, which would become "tricky": The 0.8A is close to the specified required current. You can try and see what happens. But be careful: Things might be different when the battery is less full.

All PIs have a voltage regulator. Several in fact. YOU power the PI with 5V, internally it needs (at least) 3.3V, 1.2V, 1.8V and 2.5V. Each is provided by a voltage regulator.

On the PI 1, all of them were provided with linear regulators. Those are inefficient, and one or two of them were replaced by a switching regulator on the PI 2.

It's possible that you see a physically big capacitor on the PI 1. Two options: They found a physically smaller version. Or they decided that such a big capacitor was no longer needed due to the different setup of the RPI. Suboption of the latter: that big capacitor was never really needed anyway....

(I know I have a PI 1 lying around here, that has an EXTRA capacitor soldered on, because (never do this at home!) when hotplugging stuff the pi would otherwise reboot.....)

Heh.. I knew my smartphone is not a good alternative test case for the pi2mB for a simple and safe example for current requirement (low powerbank output, reference from its power adapter spec in result boot the phone for a few seconds. As a guide picking out the right powerbank from the store, but was useless when I test on a branded sanyo powerbank and It powers the phone with either 1.0 and 2.0 Amps)

The power sags as in there is extra current flowing? What would happen when the battery is not full or becomes less full sir?

If it powers down I wont damage the pi2 right?

Sorry I can manage to do a trial and error test as I only have 1 pi and still gaining knowledge other than that I got other stuff that’s taking my time.

The 5v current is filtered by the regulator to what the pi2 requires? so either 1A or 2A is adequate and can be filtered by the regulator safely?

I got an eye candy getting a large mAh capacity, 2 usb port; 1 for the pi2mB and 1 for a usb hub . Still pending on infos.. Haha I guess it happens.. when u got a lot of device becomes unusable