If you’ve room in your bag or pockets for a portable battery bank, you need never run out of smartphone juice again. But it's worth choosing one consciously: a good battery bank can take a few people to a festival, powering everyone's speakers and phones, or get you through a week's driving abroad with your maps app for navigation. A lesser bank just gives a few hours' juice when you're stuck. Here's what to look out for before you buy...

There are battery banks in all shapes and sizes: from lipstick to cats, if you're into things that look like other things. But the cheap and small ones usually aren’t as good: make sure you read the number of mega amp hours (mAh), as this tells you how much charge the battery can take.

Low battery

Capacity is key

The latest smartphones have bigger batteries than their predecessors, meaning older battery banks (and their claims on how many charges they'll give you) are a bit out of date.

Phones vary in capacity, but most of the big brands' flagship phones from the past year or so float around 3,000mAh. Next year’s phones will hold more. And so on. 

To really ensure you don’t ever have to commute without your beloved screen, you should get something that will give your phone a few charges. Unless it actually fits in your wallet, don’t bother buying anything below 3,000mAh, you’ll just have to remember to charge it after every use, and you will of course forget.

10,000mAh is respectable, and you can get one in the shops for around €30, or cheaper online from eBay or Amazon. If you can spend more, and wait for delivery, you can get up to 30,000mAh, enough to keep the whole family from having to make eye contact for a few days. But check the size and weight before you buy, or you might end up (like me) lugging a brick everywhere you go just because "30,000 is better than 20,000". 

Hard luck of the Irish

If you’re planning on buying from Amazon, there’s an obstacle: new rules restricting delivery of items to Ireland, including lithium batteries.

Amazon delivery restrictions
We're not the only ones who can't buy lithium batteries: light bulbs are a different story

We Irish are no strangers to the label 'doesn’t deliver to Ireland'. There are workarounds - such as using parcel services giving us a Northern Irish address. In the case of the battery restriction, unfortunately, this doesn’t work. Amazon won’t deliver lithium batteries to NI either.

But there's one workaround:

An Post’s Address Pal is like the parcel services you may already use, but gives a mainland UK address. It’s slower than other services: taking between four and five working days to deliver, but maybe worth it if the product has free UK delivery.

If that's too much messing, buy from an Irish site or in shops: bear in mind, a lot of what's on the high street is low capacity. If it doesn’t say the mAh, assume it's low. 

Other features top check

Check the output of the bank and the needs of your device before you buy, particularly if you want to charge devices like tablets or laptops. 1 Amp is not going to be enough for a tablet - and it’ll be slow to charge your phone too - so check if there’s a USB 2.0 or better. But you don't need to buy a bank that says it's approved for your specific model or brand. 

Some of the beefier banks can even charge a laptop at 30W. To check if that means you too, pick up the fat bit (adapter) of your laptop charger and read the tiny print. If it says 30W or less, (and this is the output of the battery bank you're looking at) you’re in business. 

Other features you might like, which you might not find on the high street, are newer ports: such as USB Type-C, Apple’s lightning port, Qualcomm's Quick Charge (if your device is compatible) or Google's USB-PD. 

Ah, we can carry enough charge for ten phones in our pockets, but we're still no closer to decommissioning that drawer full of slightly-different cables.