Portable Power Solutions

[gothiclord]

Ok so I have been playing with my RPI for a month now, and have managed to get it doing all sorts of useful stuff, from being a web and cloud server, to acting as a VPN and wifi router.

Now I am finished playing, and want to get down to business, I bought the RPI for many reasons, but mainly to try a few experiments.

I am looking for a form of battery that can be used to power the RPI for portable use, for several hours at a time. Is this something that has already been done, or could be done, to power the RPI on the move, away from electrical sources (i.e. on a camping trip)?? and how long could such a device last??

[owencook]

I bought a 4xAA batter holder with an USB socket, here is my Au supplier item;
( http://www.jaycar.com.au/productView.asp?ID=MP3083 )

So 4xAA @ 2250mAh will run it for a couple of hours

[gothiclord]

That looks like a pretty cool solution, I have seen a number of rechargeable USB power packs, which I had been considering (designed as portable phone/tablet chargers). My main issue now is knowing how long the battery will hold up when running the RPI

I do have a portable solar solution planned (costing under £30), but will need a rechargeable battery pack for when the great british weather strikes.

Is there a rule of thumb on how long a battery will last based on the mah capacity? (of course I realise this would be reduced when using USB devices on the RPI)

[drgeoff]

Is there a rule of thumb on how long a battery will last based on the mah capacity? (of course I realise this would be reduced when using USB devices on the RPI)

Even better than a rule of thumb is the exact science.

Power consumed by RPi = 5 volts multiplied by current drawn.

For battery: Power multiplied by hours = battery volts multiplied by Ah (mAh/1000): Rearranging that gives:
Battery life in hours = batt volts multiplied by batt Ah divided by power consumed by RPi.

If battery is connected to RPi via a voltage regulator or converter then its effect needs to be taken into account.

A model B RPi is usually reckoned to draw 0.7 amps.

A 5 volt 2 Ah battery would therefore last 2 divided by 0.7 hours.

A higher voltage battery also rated at 2Ah connected via a linear voltage regulator would also last just under 3 hours.

A higher voltage battery (B volts) also rated at 2Ah but connected via a perfect switching regulator (100% efficient) would last proportionally longer: 2 times B divided by (0.7 times 5). In practice no switching regulator is 100% efficient. So reduce the time in line with actual efficiency.

If battery has capacity different from 2Ah scale the time to reflect that.

Note that putting cells in series (to increase the voltage) does not increase the Ah figure to use.

Also be aware that most quoted battery capacities are on the optimistic side and that capacity reduces with age so build in another reducing factor.

[gothiclord]

Ok so if I got this right, you divide the Ah capacity of the battery by the Ah draw of the device, so a USB battery pack with an 9Ah capacity & 5V output, should last just under 13 hours.

So in theory, combining this with a solar charger, I should be able to run the RPI 24/7, without drawing power from the mains (of course battery capacity and solar output dependant).

[Frans82]

Hi all,

I've used several RasPi's in a 12V mobile system.

With bluetooth dongle connected and 3G modem (for SMS) they are drawing 310 mA average at 12V
I'm using a standard (cheap) LM2596 DC stepdown switching regulator to go to 5V.

I've run this setup on this battery: http://dx.com/p/12v-9800mah-rechargeabl ... tery-90998
This will last anywhere between 11-14 hours.

I've also run this setup on this battery: http://www.deben.com/lithium-polymer-ba ... -pack.html
This setup lasts approximately 30 hours.

Hope this helps!

Cheers,

Frans

[gothiclord]

Now the Lithium Polymer idea is nice, my portable solar panel puts out 12v, and I actually do have a spare LM2596 and LCD voltage display, just sitting in my study (spares from building variable voltage e-cig mods). My only hang up with it is the cost, but may be a nice addition later on down the line.

[drgeoff]

Ok so if I got this right, you divide the Ah capacity of the battery by the Ah draw of the device, so a USB battery pack with an 9Ah capacity & 5V output, should last just under 13 hours.

Yes, if the battery is 5 volt you divide its Ah capacity by the current (A not Ah) drawn by the RPi.

[jphphotography]

I've been using one of these here and there http://www.usa.philips.com/c/cell-phone ... 72_17/prd/
A local liquidation place had them on for cheap so I bought a few of them, great for camping too! They already come with a micro usb end so no need to hack a cable together.

Oddly enough I was just looking at those Lithium packs on DX.com like 2 minutes ago! I'm running my "dev" pi off of 12V with an LM2596 board that a buddy of mine made (has RTC and serial) http://slavtek.com/m/img/pi/pi_ps.jpg he should have the pcb files up at some point if anybody else is interested.

I'd be curious to hear about your solar plans, I picked up some auto buck/boost boards from ebay for my own solar battery idea.

One of my main worries is what happens when the batteries die, how gracefully will the Pi go down? What risk of corrupting SD cards etc.

[Frans82]

I've integrated the PI into several products/concepts. None (!) of those close the PI down properly. They all just let the battery die or disconnect the power supply.

I have never had one corrupt SD card. Thats why I don't bother anymore closing down the PI properly. I just disconnect.

I consistently use this SD card: http://www.memorystunter.nl/contents/nl ... kaart.html

Cheers,

Frans

[gothiclord]

the solar panel I have is http://www.amazon.co.uk/gp/product/B005 ... automotive, which should be able to kick out enough juice, during daylight, to charge a USB battery pack.

The other thing to take into consideration, is that as long as there is light (it doesn't have to be sunlight), these things will produce electric (although using electric lighting defeats the point here)

[m0rgo]

Another factor to take into consideration is the type of battery you intend to use.

Although a particular battery will have a Ah figure, a lot of larger capacity batteries do not like being discharged completely and should ideally not go much below 50%

If you want to make full use of the potential Ah rating of a battery when away from a charging source, I'd recommend the 'Deep Cycle' type; which will tolerate being discharged closer to the theoretical full Ah rating.

My current set up, for remote use with amateur radio equipment, involves a couple of motorcycle sized lead acid gel batteries, with a 12V vehicle USB charger to connect to the RasPi.

[cleverca22]

this may also be usefull to read: http://spritesmods.com/?art=rpi_arcade

its basically an rpi with a battery pack, chargeable off usb
2 lcd displays, and a few buttons, and soft power on/off

[PercySwanson]

Ok so I have been playing with my RPI for a month now, and have managed to get it doing all sorts of useful stuff, from being a web and cloud server, to acting as a VPN and wifi router.

Now I am finished playing, and want to get down to business, I bought the RPI for many reasons, but mainly to try a few experiments.

I am looking for a form of battery that can be used to power the RPI for portable use, for several hours at a time. Is this something that has already been done, or could be done, to power the RPI on the move, away from electrical sources (i.e. on a camping trip)?? and how long could such solar panels last??

hello friend I know thread is bit old but have you got portable power solutions? I am working on similar project so can you give some useful tips? Waiting for reply thanks in advance:)

[JesusDoyle]

That looks like a pretty cool solution, I have seen a number of rechargeable USB power packs, which I had been considering (designed as portable phone/tablet chargers). My main issue now is knowing how long the battery will hold up when running the RPI

I do have a portable solar panels solution planned (costing under £30), but will need a rechargeable battery pack for when the great british weather strikes.

Is there a rule of thumb on how long a battery will last based on the mah capacity? (of course I realise this would be reduced when using USB devices on the RPI)

I do agree with you.. Solar power solution is ideal.. Even I am using solar power as portable charging..

[drgeoff]

I do agree with you.. Solar power solution is ideal.. Even I am using solar power as portable charging..

If you were looking out of my window right now, you might change your mind.

[Ravenous]

I do agree with you.. Solar power solution is ideal.. Even I am using solar power as portable charging..

If you were looking out of my window right now, you might change your mind.

Funny when someone resurrects an old thread from the Spring & Summer, and now it's mid-winter!

Solar is obviously a non-starter. Wind power would work today though! Or a water-wheel powered Pi...

[mattvenn]

I just did a tear down and test of a tecknet 3300mAh usb power pack: https://github.com/mattvenn/tecknet
With a Raspberry Pi model B it lasts for about 6 hours.

[Ravenous]

VERY interesting analysis, thanks for posting it. (The linked article about fraud batteries and dodgy chargers is useful too...)

[RredCat]

I want to make my device portable and looking for portable power as well.
I read in the specification that my Raspberry Pi 2 Model B needs 5v and 1.8A output for work.
I have a number of power banks that have next outputs: 5v and 1A, 5v and 1.5A and can buy 5v and 2A or 5v and 2.1A.
But I can't find 5v and 1.8A.
Powerbank with which output is better for my Raspberry Pi 2 Model B?

[drgeoff]

1. You don't need to exactly match the current requirement. You should always use a power source which can supply more than the RPi needs. The RPi 'pulls' what it needs. The PSU powerbank does not 'push' the current stated on the label.

2. A RPi does not consume 1.8 amps. About half of that is enough. But if you have peripherals plugged in .....

[mosespi]

owencook: I would not use those 4AA USB output packs with the Pi, most are NOT regulated, including the link you provided from jaycar. May or may not work well, depending on which Pi and how sensitive your USB devices are to an actual 5v supply.

A switching regulator (like the LM2596) is a good way to power the Pi. Some graphs from my UPS project to entertain you below. These run times are a good real world example of what you would expect from batteries feeding a switching regulator, which is about the cheapest and most flexible way to power your Pi.

Newer runtime tests on Pi 2 with 8xAA Batteries 12 hours 25 minutes!
and almost 10 hours on 6 x AA batteries!



Small 1.2AH SLA Battery with Pi 2 and 7" Foundation display 1 hour 41 minutes!


7.0AH SLA Battery with Pi 2 and 7" Foundation display a minute shy of 19 hours


Regards,
-Moses