USB POWER BANK // PORTABLE POWER SUPPLY

That is absolutely wrong.

The Amp-hour rating does not necessarily relate to the AMP-rating of the powerbank.

I have a power-bank where I can put my own cells in. I put in 6 good cells, so it is now about 20Ah (at 3.7V).  The converter for 5V is reasonably efficient and capable of 2A, so this one will power a pi just fine. But in this case the Ah rating is "20", and the current rating (AMP above) is only 2. The 'pi requires a current rating of about 0.7A. But because phones will charge anyway, people get away with claiming more than is technically possible. So you can buy 2A chargers that just tell the phone "I'm 2A", but then fail to deliver. The phone silently goes along.

mAh ratings are even worse when it comes to exagerating the numbers: most people are unable to verify the numbers.  I have 18650 cells that claim 5500 mAh, but are 600mAh in reality. Allow me to power my 'pi from that battery for a few minutes when I get to work. It'll work. (I'll connect the 4.2V from the battery to the 5V of the pi, and it will work like that. This saves a conversion step between the 3.3V-4.2V of the battery to the "official" 5V that the pi needs, and then back again to 3.3V, 2.5V, 1.8V that the pi actually needs internally....) (USB devices might not work: many need something closer to 5V to work. ).

Update:

I call my "raspberry pi2" "too". As the "officially 5V" line is below 4.65V, the power led is off. But...

too:~> uptime

12:40:32 up 6 min,  1 user,  load average: 0.00, 0.01, 0.01

too:~>

it works just fine. I was planning on taking an extra one of those batteries and make sure it was fully charged to make sure that this experiment went without a hitch.... I forgot. The battery was discharged yesterday to test a charger, but we didn't get around to fully charging the battery again. The battery is now at 3.7V, and the 'pi runs just fine. It has connectivity over the ethernet, my "HDMI->VGA" dongle will not work because it requires something closer to 5V. Similarly USB devices might not work, as they too require something closer to 5V. But for me, this construction is just fine. (I spent 5 minutes typing this: uptime is now 11min).

Update: After posting I tried running 4 processes at once. It ran for 22 minutes before the battery ran out. Note that although the battery claims 5300mAh, it is in fact only about 600mAh. And it was not fully charged. Also note that there was no  battery protection circuit anywhere: the pi continued to try to run when the battery got below 3.0V. This is not good for such Lithium Ion batteries. (but you can get away with it if you charge it immediately with the correct procedure....)

Hi Roger,

This is great to see. Good experiment! Will be interesting to see how long it lasts on a fresh battery. Quite long I expect if the battery is currently at 3.7V and it is still functioning.

Maybe several hours possibly : )

I expect about 40 hours on my 20Ah pack. (provided I don't use the 5V output of the power bank. Or if I only use that 5V for things that really need it like USB devices.

Update: the RPI ran 1:35 (one hour thirty five minutes) on the "about 600mAh shitty Chinese battery" now that I properly charged the battery before starting the experiment.....

P.S. Both the RPI and the battery seem to have survived the reverse polarity incident.... :-) :-(

Greg Fenton: will it work? Im no electrician but the vilros adapter indicate outputs 2.0 DC current and MaH is another thing that I don’t know about.

Wow roger I had that kind of thought well a lot hehe.. one of em is where that batteries of an AA that is packed like the RC car batteries as a jump start to boot the pi2 for several minutes or so, then a usb hook up to that battery, kinda like how smartphones are powered while charging, but I don’t know how to accomplish that hehe, but watching from youtube about using a USB powerbank most of it are on pi1.

Im trying to get this approach which is spot on! I want to do this with my pi2mB

https://www.youtube.com/watch?v=6nh11axTXQo

From Pi1 user manual it is stated possible and etc to use a USB mobile charger and models varies in mAh. All videos I found are all on pi1

For one on using powerbank is this

https://www.youtube.com/watch?v=x5e9woT5pEQ

But from pi 2 model b manual out of the box state that it is not designed to be powered from a USB port on other connected equipment, that it may result in malfunction and from Vilros manual requires a power supply of 5V providing atleast 700ma similar to pi1 manual

What worries me the most pi1 is somewhat 1^st Gen and in still on a testing phase just like PSP back in the days haha pardon me if im out of topic, and pi2mb is smaller in size with new features and has a separate RAM which I think voltage circuitry is tweaked out of the factory, buuuut it has a protection circuit when powered from the micro usb port..

If only there’s some vid on pi2mb using a powerbank will push me forward on my next thing plus I got this habit of burning my mod which scared me lol

I will charge up one of my USB power banks and run a script on the Pi that asks for a web page once a minute.

The first time it connects I will class as my start time, the last time it connects I will class as my end time.

I will let you know the outcome.

I will do the test with 2 power banks, one on a Pi and one on a Pi 2 to test the difference.

Neither will be running a desktop or have HDMI turned on.

I hope this will settle the issue.

Greg

What the pi2 manual tries to say is that powering the Pi (1 or two doesn't matter) from a normal USB port on your PC is not recommended.

The 'pi will use  up to 700mA which is over the maximum or 500mA that USB ports should be able to provide. And because the data lines of the raspberry pi power-port are not connected, a PC should actually limit the current to about 100mA and that's definitively not enough for a pi. Normal USB devices then request: "may I have more than 100mA?"  to which the PC replies: sure, go ahead! But in practice, most PCs will just provide 500mA or more even before the device has asked for more than 100mA.

All this does not apply to "chargers" that are clearly marked 1A or more.

Nod* default 5v usb 2.0 that draws from a PC

I thought “atleast 700mAh” is not more than that, but it’s a mod discussion right..but still im afraid to do this mod..heh. Great and easy to understand on the PC USB explanation. Thanx

Does that mean a power source more than 700mA is safe for the pi2mB?

I tested a 2-in-1 desktop charger that charges Li-ion 1320mAh battery for a phone that can be a power bank as well, when the battery is fasten to the charger. The USB port output 5.2V 800mA

I tested this on my phone 600 MHz Cortex-A8 which feeds DC 5.0V/1200mA to support my thoughts about pi2mB USB current, I did a cold boot on my phone, but wasn’t enough it only last for less than 20-30 sec then powers down. This could be the charger is not drawing enough current. Will testing this on pi2mB safe?

I tested the phone with the 2 usb ports 1)1A 2)2.1A of the power bank and both port testing 1 by 1  charges the phone, and this smartphone has a built in charging script if it is not enough power it will prompt me a message and its built for a usb powerbank right?

Does pi2mB have a voltage regulator? Because I saw a vid this person was using an additional board for voltage regulator on his pi1 don’t know if its model B or the default pi1 model, then power it up with a power bank.

Will this be the same result as with pi2mB? Meaning without an extra board with regulator

I did a mod from a PSU 12v DC to power a small car air compressor that feeds from a cigarette lighter power slot, changed it, so that I can use the house power outlet with a 3 pin plug, without knowing its mAh it worked this was because it’s a really direct current.

greg, do a video clip while youre at it..if you don't mind, please