Smartphone battery packs: can a USB power pack beat the festival battery blues?

Darien Graham-Smith
16 Jul 2014

Until recently, there wasn’t much point taking your smartphone to a summer festival. With tens of thousands of people converging in the middle of the countryside, it was impossible to get a signal, and your battery was likely to expire on the first day anyway.

But things are changing. Coverage has improved markedly in recent years, and event organisers are starting to embrace mobile technology with official festival apps and onsite charging facilities – a more popular attraction than many of the bands, judging by the size of the queues.

Lowering the bar

For this year’s Glastonbury Festival, EE came up with a clever little thing called the Festival Power Bar – not a snack, but a baton-shaped battery costing £20 that could be easily carried around and used to recharge your phone over a regular USB cable as needed. Fully discharged bars could be swapped for freshly-charged ones at the EE tent, so you could keep on trucking without too much hanging around.

Predictably, the bars sold out long before the festival opened. Unfortunately, I suspect those who invested found themselves traipsing back to the exchange point rather more often than they’d anticipated.

That’s because the rated capacity of a Power Bar is a rather weedy 2,000mAh. According to EE, this is enough for “five hours of charge”, whatever that may mean. In practice, it doesn't take a senior wrangler to realise that this isn’t going to fully replenish the 2,600mAh battery of a Samsung Galaxy S4.

What might surprise you is the scale of the shortfall. When you discharge one battery to charge another, a lot of energy is lost in the conversion. How much charge you lose will depend on all kinds of factors, but a 30% drop between battery pack and phone is entirely plausible. In other words, using a mobile power pack is tremendously wasteful of energy  and it means that a moderate smartphone user could charge up from a Festival Power Bar at the start of the day and still find themselves on emergency rations before the Kaiser Chiefs finally get around to playing "I Predict A Riot".

High-capacity power packs

Of course, larger power packs are available. A friend of mine braved this year’s Glastonbury with a Proporta USB TurboCharger 7000 – a compact little battery roughly the size of a portable hard disk. Although rated at three and a half times the charge capacity of the EE Power Bar, this still only managed to charge her HTC One twice before it was completely drained. Happily, since the power pack itself charges by USB, she was able to refuel it at the recharge tent on the Saturday, and thus get through the festival.


My partner and I meanwhile had invested in something meatier: the Anker 20,000mAh Astro Pro2 charger. This wasn’t actually our first choice, but for some reason the 22,000mAh pack we originally ordered wouldn’t charge my Galaxy S4: I gather that some devices are finicky about their power requirements, and won’t charge if the voltage and current aren’t exactly as expected.

The Anker is a serious piece of kit: it's the size of a novel, it weighs a chunky 510g and it set us back fifty quid. But it charges all our devices, and also boasts a natty display showing exactly how much charge remains. We each got two charges out of it before it died – a more impressive feat than it may sound, since I’m still using my high-capacity 5,200mAh battery.

On account of its huge capacity, the Anker power pack charges from the mains rather than via USB, so at first we feared we wouldn't be able to recharge it at the tent. Thankfully, a nice man found us a spare three-pin socket tucked away in the corner, enabling us to refuel the Anker in a matter of hours, and stay in touch for the rest of the festival.

Power to the people

We were disappointed that our power packs didn’t make it through the entirety of Glastonbury, but they did allow us to minimise our time spent queuing at the recharge tent. If you’re going away for a shorter spell, a portable battery may be just what’s needed. It might also be a sensible thing to keep in a car in case of emergency – although official advice seems quite variable as to how long a lithium-ion battery should be left unused in a charged state.

What can be said for sure is that until battery technology develops a bit further – or until really huge battery packs become the norm – you’ll still need to use your phone sparingly at festivals. That, or resign yourself to queuing up for a periodic juice boost.

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