The Raspberry Pi is easily the most popular mini PC by numbers sold – according to reports its quickly closing in on 1.5million. But while it’s normally powered by an AC USB power brick, there are plenty of occasions when battery power would be far more convenient.
One simple Raspberry Pi portable power option is what’s often sold as a ‘USB emergency charger’, which is basically two AA size batteries connected to a step-up DC voltage converter, outputting 5VDC at up to one amp (1A). It’s not a huge amount of power but enough to keep a Raspberry Pi powered up. It basically takes the 2.4/3.0V battery voltage of the two NiMH/Alkaline batteries inside and ‘steps it up’ to 5VDC, the USB voltage standard required by the Raspberry Pi.
Now obviously, we’re not talking about including a monitor, keyboard or external storage in this little power setup. But if you’re thinking of outdoor, low-power, single-function applications for you R-Pi, the USB charger idea is well worth a shot. It’s pretty simple to operate – install your two AA batteries (yes, they can be NiMH rechargeables), flick the switch on the side (you can’t see it in that shot), plug your USB power cable in and the other end into the microUSB port on your Raspberry Pi and up it comes.
If you’re using Sanyo Eneloop-style 2000mAh batteries, you should be able to power a Raspberry Pi on its own for around two hours. (That’s based on a power requirement of approx 2.5-3.0-watts to keep the Pi running). Using single-use Lithium batteries like Energizers would make the power source last longer – first, because of their higher capacity, but also their higher voltage increasing the overall efficiency of the step-up conversion.
You can find these ‘USB emergency chargers’ on eBay for under $2 – and that includes shipping. They’re probably the easiest, cheapest and most efficient way to portable-power a Pi (when used with NiMH cells) that you can get. There are plenty of other options including SLA (sealed lead-acid) and Lithium-ion batteries; you can even power your Pi off your car battery if you want – the trick is obtaining a clean, regulated 5VDC supply with up to one amp of current. Where you get your portable power from doesn’t really matter as long as it’s safe but provided you can get that 5VDC@1A power, you should have no trouble powering a portable Raspberry Pi (sans monitor, external storage and the like of course).
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