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so these are cheap and easily available , and voltage is written as 5V ..but im suspecting reliability ..any way to use those batteries to power raspi ?

Kamalesh wrote:so these are cheap and easily available , and voltage is written as 5V ..but im suspecting reliability ..any way to use those batteries to power raspi ?

FWIW, I'm in the process of testing out this one:
http://www.cpmspectrepi.webspace.virgin ... arger.html
Initial tests seem promising, but I need to interpose a "power switch" since, currently, the only way to remove power, after issuing a sudo shutdown -h now command to the Pi, is to "pull the plug".
Trev.

Kamalesh wrote:so these are cheap and easily available , and voltage is written as 5V ..but im suspecting reliability ..any way to use those batteries to power raspi ?

yup, they just work out of the box. I can get a few hours from a cheap one (£7.99) while using its WIFI router function. I don't know how long this one (£15.99) can run a pi for, I got bored of waiting for it to run out after several hours (it was still displaying 3/4 battery life after 3 hours).

Interestingly the first one I mentioned (not tried the second) will act as a UPS, you can charge it while it is powering the Pi, it also has a on/off/wifi switch.

So is there a way to know from raspberry pi abouthow much battery backup is left ,like the battery indicators found in mobile phones ...also I hear complains that some of these batteries provide low voltage near end

Kamalesh wrote:So is there a way to know from raspberry pi abouthow much battery backup is left ,like the battery indicators found in mobile phones ...also I hear complains that some of these batteries provide low voltage near end

most of them have a series of LED's indicating power level, maybe you could set up a photodiode to monitor each one (or just monitor for the 2nd to last one going out)

Powerbanks work fine as power source for a RPi

Especially the ones that allow charging while powering the RPi, making it a cheap UPS solution.

The chinese (dx, banggood, miniinthebox, ebay) sell all sorts of these devices for low prices. Not all are that good, one died on me very quickly. But another one, a 20000 mAh (exaggerated ofcourse), lets a Rpi run for more than a day. It has a power indicator with a led bar of 5 leds, I recharge when only one is lit. Perfect for a timelapse on a location outside. I use it for more than half a year now and it is still working fine.

thanks for all ur replies , im trying to make a robot with it ...

Kamalesh wrote:thanks for all ur replies , im trying to make a robot with it ...

Then I definitely recommend the E-synch one I linked earlier, you can use that as your WIFI connection to a mobile phone or tablet. (separate power supply needed for motors)

(I'm doing the same, check my latest Dalek post for how to set up a webserver (which I am using as the control interface)

Not all of these work so well as a UPS. If AC power is removed, there's a brief drop in the 5V when it switches over, possibly rebooting the Pi. Oh and if your's doesn't have a switch, Adafruit (of course) has a short USB extender with an in-line switch.

I use both "Patriot Fuel + 5200mAh" and inexpensive asian ones, to good effect.

See

http://www.mikronauts.com/robot-zoo/sprite/

and

http://www.mikronauts.com/robot-zoo/elf-2wd-pi-robot/

Kamalesh wrote:so these are cheap and easily available , and voltage is written as 5V ..but im suspecting reliability ..any way to use those batteries to power raspi ?