# Will any external battery power a Raspberry Pi?

I am working on a project that needs the Raspberry Pi to work without a mains connection.

I have considered buying a 50000mAh USB power bank. Would this power a Raspberry Pi, and if so, would it power it for more than 24 hours?

• The power requirements depend somewhat on the specific Pi model (the B+ and A+ use less power than the B and A models; the A variations also use less than the Bs). – TomG Jan 10 '15 at 23:17
• Thanks TomG, I was going to buy an A+. Would it still use around about 5V power? – Joel Jan 11 '15 at 0:01
• Yes, they all run on 5V. – TomG Jan 11 '15 at 0:02
• My Model B has been running fine so far on 4 1.2v NiMH batteries for just over 20 minutes. Extremely efficient and hasn't given me any power warnings yet – TheJamaicanGuy Jan 11 '15 at 13:13
• It lasted for 2 hours 40 minutes before it started reboot-looping. Quite impressive – TheJamaicanGuy Jan 11 '15 at 16:49

Yes, most (but not all!) USB power banks are capable of powering a Raspberry Pi, since they usually have an output voltage of `5 V`. And yes, by using a (quite large) `50 Ah` power bank, you can definitely expect your Pi to run for at least `24 h`. See the long answer below for reasoning and further relevant aspects.

According to actual Raspberry Pi power measurements, the Model 3B+ consumes about `520 mA` when shooting 1080p video.

We first compute the electrical power of the Raspberry Pi in watts:

``````0.52 A * 5 V = 2.6 W
``````

Next, we have to consider the fact that the mAh rating of a power bank refers to its nominal cell voltage (which is `3.7 V` for a typical lithium-ion based power bank), and not to its output voltage of `5 V`. Thus, a `50 Ah` power bank has a capacity of about

``````50 Ah * 3.7 V = 185 Wh
``````

The expected runtime for your Raspberry Pi therefore is

``````185 Wh / 2.6 W = about 71 h
``````

The actual runtime will however highly depend on many unpredictable aspects like CPU usage, WiFi usage, connected hardware etc., so we'll just assume that the actual runtime will be at least `50 %` of the expected runtime. This also gives us a safety margin.

``````71 h * 50 % = about 35 h
``````

So, the actual runtime of your Raspberry Pi should be somewhere between `35 h` and `71 h`, depending on your setup. YMMV.

Please make sure to run sufficient tests with your power bank before actually using it in production!

## Further aspects

• Not all power banks are suitable for running the Raspberry Pi. Some will shut the power output down after some time, or interrupt the power output for a short time when you connect the power bank to mains.
• Many power banks can't be charged and discharged at the same time.
• You can even use a power bank as full-fledged UPS for the Raspberry Pi. All you need is a compatible power bank. If you don't already have one, the website lists supported brands.

As long as the power bank outputs 5V it will power the Pi.

It claims 50000mAh so it claims 2.5 amps per hour for 24 hours. Assume it will deliver half that so 1.25 amps for 24 hours.

If that is enough or not will depend on what you have connected and what the Pi is doing.

• Hi Joan, thanks for your answer. I want it to record from the Raspberry Pi camera module. Do you think this would work? ebay.co.uk/itm/… Also, what's the maximum SD card capacity for the Pi? – Joel Jan 10 '15 at 21:59
• I don't know about SD card capacity and can't comment on the suitability of any power bank, having no experience of them. The camera module uses 250mA so you should be OK. Hopefully together with the Pi you'll be using about an amp. – joan Jan 10 '15 at 22:04
• @joan I heard that the USB 2.0 cable have got a limitation of 500ma, whats happend if the raspberry needs more than 500ma? For example because use a camera, a wifi adaptar, etc. The 500ma limitation is apply to this or only to give power from raspberry USB? – dlopezgonzalez Nov 8 '15 at 13:59
• @dlopezgonzalez That's news to me. I know PC USB ports don't have to supply more than 500 mA. I've never heard that the cable is limited (except by flimsy wires, which is for cheapness). – joan Nov 8 '15 at 14:49
• Ok, so a power back with 5V and 2A in output in the specification will be provide 2A to the raspeberry without problem (or arduino). – dlopezgonzalez Nov 8 '15 at 15:32

Something to keep in mind is that some power packs will shut themselves down if there isn't enough of a power draw. For example, I have a New Trent PowerPak+ 13500mAH power pack, which shuts itself off after a couple minutes if it's only powering an Arduino or Raspberry Pi. (Plugging in my hungry smart phone prevents this)

Any USB power pack will certainly run it, as long as it doesn't shut off. As previously suggested, you can get an inline USB power meter, and if you take a measure of your Pi's power draw, you can calculate the run time of your setup.

• My first thought was a workaround could be to run a low-priority background process with a busy loop that keeps the CPU usage at least 40%. My second thought was xkcd.com/1172. – Carl Walsh Mar 2 at 18:21

Sources on the Raspberry Pi forums say the Raspberry Pi uses approximately 500mA add in the 250mA for the camera module, and round for a safety margin equals approximately 1A. A 50,000mAh battery will run 1A for 50 hours. Even with additional safety margin that is plenty to run for 24 hours.

• Is it possible to get the pi going on a lower mAH psu? Around 300-400mAH? – TheJamaicanGuy Jan 11 '15 at 11:31
• @TheJamaicanGuy I'm not sure, you would have to experiment. Try turning off every possible thing that uses power. Nothing plugged into usb, minimize use of the CPU, and perhaps even try turning off the red indicator light if possible. – user1558604 Jan 11 '15 at 13:59

I expect the battery you propose would be able to run your Pi for 24 hours. Depending on the model of Pi and what other equipment you have connected e.g. a USB keyboard would also draw some power, as would the camera module. I tested a Model B+ running from a 9,000 mAh battery which was configured with a WiPi adapter, running as a web server and WiFi hotspot and it ran for over 12 hours before the battery was exhausted. I suggest you consider trying the Model B+ and the Model A+ (which consumes significantly less power, but may not meet your project's requirements in terms of connectivity, USB ports, or RAM).See http://www.raspberrypi.org/products/ for info on the different Pi models.

I use inline USB power meters to monitor the power consumption. My current favourite is http://www.portablepowersupplies.co.uk/portapow-usb-power-monitor-v2/ and I have 10 which I use for my testing of Pi's and power consumption. You might find one of these helpful in your testing. Connect it inline with the power supply to the Pi.

The Raspberry Pi FAQs also has several topics that seem relevant e.g. on the power consumption of the camera unit and on power requirments generally http://www.raspberrypi.org/help/faqs/

In answer to one of your related questions, I use various sizes of SD-Card, up to 128GB in the older full-sized Model B, and 64GB micro-SD cards in the newer A+ and B+ I use branded, high-speed and relatively expensive models e.g. from Kingston, SanDisk, etc. Ask a separate question please if you'd like to know more.

And a final suggestion for now, if you want to be able to charge the battery while powering the Pi relatively few battery packs are capable of doing so. Again, you're welcome to ask a separate question if this topic is relevant.

If your powerbank can't give you that much power use a 12 volt lipo battery with BEC circuit. Try a BEC with 5V 3A output. In this way you can make your pi portable enough.

Check out this BattPi case on kickstarter

https://www.kickstarter.com/projects/719364198/raspberry-pi-case-with-real-time-clock-battery-and