When building autonomous project, providing enough power is the key to success. Our original project used quite beefy juice canister, 10000 mAh was a must as we had RPi 3, video stream, and two DC motors running at the same time. As we're now down scaling the whole project, our power source should shrink too. Or not?

Well, we're going to find out the only way we can: let's try it out! First of all, we'll pick smaller power bank which still has two USB outputs and a power button. Of course, one of those outputs has to be able to give us more than 2 amps while maintaining 5 V, so we'll pick manufacturer we can trust, keeping in mind the price/quality ratio :-)

Tadaaa, our first pick is RealPower's PB-6k 6000 mAh power bank - a German company should deliver, right? Once we've got our hands on it, we cycled it few times through charge - discharge stages, just to make sure it's going to be consistent through the tests. And now, the fun part starts!

Image by RealPower

First we installed Raspbian Strech Lite (AKA headless) version on a SD card and enabled WiFi and SSH on it (instructions on how to do that coming soon - don't worry, it's easy-peasy). The only thing added was a crontab line which is logging the uptime (yes, we'll share that one too) and we're set to go - all we have to do now is wait...

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So, one day and 14 hours later, our test was officially finished - not bad for a first run. While we're charging the power bank, it's time to try some tricks. It appears that HDMI connector onboard RPi Zero is pretty hungry even if nothing's connected to it, so let's turn it off. Fortunately, that's easy when running Linux, all you have to do is to add this line:

/usr/bin/tvservice -o

to /etc/rc.local. And we're good to go one more time...

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One day and 19 hours later we've learned that one line in one file saves five hours of uptime. Wow! We could save a little bit more by turning off a power LED, but is seems we'll lose more than we'll gain, so we'll forget about that one, as our uptime looks quite good right now.

Let's give our Zero something to do - we'll add 5 MP camera to it, and we'll run start script which will start onboard command server and video stream. How long will it hold out now?

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Of course, not so long, but 22 hours is more than good enough for us, we've nailed the power source at the first go. Yay!