It was only a few years ago that most of us looked forward to escaping the phone and computer for a week or two when we went away on our caravan holidays.

But then along came smartphones, which meant that your phone was now your camera, music player, web browser, link to Facebook and Twitter, and even a sat-nav.

Next came tablets, which are basically the same but with much more usable screens. Somewhere between came Kindles and other e-readers, which seem a little limited compared to tablets but come into their own when reading outdoors in bright sunlight, thanks to their reflective epaper screens.

The trouble is that hammering these devices for any length of time rapidly depletes their battery. And there’s nothing more infuriating than getting to the last chapter of a novel only to find that your e-reader is out of juice. Not something that happens with a good old paperback.

Touring with tech

Of course, if you’re sitting outside your van it’s easy to plug in your device.

But what if you’re at the beach or if your mobile-based sat-nav fizzles out halfway through a long walk? Clearly, being able to recharge your device on the move is pretty essential.

Fortunately, portable power banks are now readily available, very affordable, and many are small enough to keep in your pocket just in case.

Better still, most modern devices are designed to be charged from the 5V output of a USB socket, so one power bank with a 5V USB output will handle almost all of your phones, tablets and other gadgets.

Laptops tend to be the only exception, because they require higher voltages – typically 16-20V – to run or be charged.

Perhaps a power bank’s most important property is its electrical capacity, which is expressed in milliampere hours (mAh). The bigger this is, the better.

Low-capacity packs may only have enough stored energy to give a mobile phone a temporary boost, whereas larger-capacity packs will be able to fully charge a mobile – from flat – several times over, and service the needs of more electrically hungry tablets.

How we tested the contenders

We not only considered capacity, but also capacity against price, and capacity against physical size – the smaller the better.

Talking of tablets, some models only allow their batteries to be charged if they sense a certain level of electrical current coming in. So it’s a huge bonus if power banks can output 2.1 Amps or more, to guarantee success with tablets. Higher-output models also tend to charge smaller devices faster.

Next on the criteria list is connectivity. Generally, phones and other devices come with a charge lead that plugs into a full-size USB socket on a computer, so it’s important that a power bank has a full-size USB socket output for these charge leads to go into.

Some power banks also come with a lead that has a full-size USB plug on one end and a micro-USB plug on the other. This is beneficial because most electronic devices – Apple products being the exception – tend to accept their charging lead through a micro-USB socket. Effectively, the USB-to-micro-USB lead means that the power bank can charge a device directly.

As for replenishing the power bank itself, most have a micro-USB socket on them so that they can be connected to a phone or other device’s charger. And plugging the USB-to-micro-USB lead into said micro-USB socket allows the power bank to be connected to a computer’s USB socket, too.

Extra points go to units with even more connection options – such as adapters that allow direct connection to Apple devices – or 12V charge leads, which make in-car charging possible.

We also considered practicalities, such as lead lengths and whether there was a pouch, or on-board storage, to keep all of those vital leads and adapters together. We preferred units with more than one output socket too.

Finally we factored-in any extra features. These range from safe operation in damp conditions, through integral torches, to being able to jump-start a car’s engine.

Powerchimp 4A – two stars

We always like dual-function products and, on paper, this is a brilliant idea.

Primarily it’s a tiny (98mm x 65mm when closed) battery charger that can boost any combination of four rechargeable AA or AAA batteries, using just a USB socket for power.

Alternatively, put in four healthy batteries and the unit can do the charging. So, in principle, provided you can get your hands on AA or AAA batteries, you can always keep your gadgets topped up.

In practice, though, charging is incredibly slow, and you need the unit, plus several packs of AA cells, to rival the charging capacity of many others here.

Buy the Powerchimp 4A here from Camera King

Cobra JumPac CPP8000 – three stars

At 140mm x 73mm x 17mm, this is the smallest hybrid power bank/jump-starter on test here. In fact, it’s almost pocket-sized.

But, predictably enough, its engine-starting punch is less impressive than its rivals’. While 180 Amps of starting current is available, it’s only for a few seconds. Then again, that’s probably enough for a good many petrol and small diesel engines.

Used for powering devices, the internal battery’s 6000mAh capacity is respectable enough and the 2.1 Amp USB output provides fast charging and means it works with tablets.

The unit itself can be charged in-car at 12 volts or via a USB power source.

Buy the Cobra JumPac CPP8000 here from Amazon

Powermonkey Explorer 2 – three stars

An eye-catching design but a rather eye-wateringly high price, too, given the modest 6000mAh capacity.

However, the unit has one trick up its sleeve that sets it apart from the rest: it’s water-resistant up to the IP67 standard. So it’s definitely worth considering if you’re seriously into your outdoor pursuits, or if a trip away always involves a couple of days of walking and wild camping.

But water-resistance aside, this is still an impressively high-spec piece of kit. The capacity means you’ll certainly get a couple of full mobile charges per unit charge, and its 2.1 Amp output ensures fast charging and compatibility with tablets.

Buy the Powermonkey Explorer 2 here from Amazon

Energizer 50805 Car Jump Starter – three stars

Like Cobra’s JumPac, here’s another unit that can revive a dead vehicle. Energizer suggests a 2.0-litre engine limit for diesels, and 3.0 litres for petrol engines.

Also like the JumPac, this unit has a conventional power bank form, although it’s a bit bigger at 138mm x 83mm x 20mm. It’s still certainly small enough to live in a car’s glovebox, though.

The unit’s 7500mAh capacity is good for two to three mobile charges and should revive at least one tablet. Naturally, the USB output is the faster, higher-output type. The 50805 can be charged by an in-car 12-volt lead or a USB socket.

Buy the Energizer 50805 Car Jump Starter here from Amazon

Olixar Powercharge Portable Charger – five stars

Practical Caravan Editor’s Choice

Remember those old scientific calculators that used to come in their own wallet? Well in size and shape, Olixar’s all-conquering charger is a dead ringer.

Its actual dimensions are 143mm x 75mm x 18mm, which just about rules out trouser-pocket storage. Coat and rucksack pockets are a different matter though.

But while this isn’t the smallest pack here, no other product provides so much oomph for its size. A stunning 15,000mAh capacity will cater for several full mobile charges and more than a couple of tablet boosts. There are also two output sockets, one of which is the high-speed 2.1 Amp tablet-friendly type.

Kodak Power Bank 5200mAh – three stars

Whilst this power bank’s 5200mAh capacity is pretty average, it’s still quite a bit of charging power for the price, and the unit’s 45mm x 20mm width and depth make it a practical contender.

It slips into a pocket nicely, even if its 90mm length tends to dig in if you have to bend over sharply. The charge lead is a decent length too, at 33cm.

So, overall, we feel that this power bank is a good all-rounder. Bear in mind, however, that the 1 Amp output means that this isn’t the fastest charger, and it rules out use with iPads and most other tablets.

Being really picky, we suspect that the lead supplied may be lost easily, because there’s no form of on-board storage.

Buy the Kodak Power Bank 5200mAh here from Maplin

Kodak Power Bank 10400mAh – four stars

Kodak’s second entry sticks to the same successful formula as its first. And, again, it’s great value for money – 10,400mAh is a lot of portable charging power for £20. In reality, it equates to several mobile charges and more than one tablet boost.

It seems that Kodak has been keen to make the most of that generous internal battery: there are actually two output sockets and, yes, they can be used simultaneously – although only one outputs 2.1 Amps for tablets or rapid charging.

As before, solid performance is backed up by a practical design. At 21mm x 75mm x 90mm long, the unit is compact and pocket-friendly.

Buy the Kodak Power Bank 10400mAh here from Maplin

Olixar Powercard Portable Charger – two stars

The name gives away this power bank’s most striking feature: at 55mm x 85mm it’s basically the size of a credit card, albeit a 5mm-thick credit card. But it will squeeze into a multi-card slot in many wallets and purses, so we have to give the unit full marks for convenience.

Unsurprisingly, this isn’t the most energetic performer here. The somewhat restrictive capacity of 1400mAh won’t charge any mobile fully, so the unit is best used as an emergency phone booster – something to keep you connected, preferably with apps and Bluetooth turned off, until you get back to base. Tablets are obviously beyond its scope, too.

Veho Pebble Explorer – four stars

Here’s one swish contender that almost took the top spot. At just 75mm x 90mm x 22mm, the Pebble fits easily in a pocket, even if it’s first placed into the smart carry bag supplied, along with the long lead and included adapters.

Talking of adapters, the usual options of micro- and full-size USB plugs and sockets are complemented by a couple of others. Many will appreciate the iPhone connector, even if the mid-sized mini-USB plug is a somewhat leftfield choice.

Great versatility is backed up by a punchy 8400mAh capacity and dual fast/tablet 2.1 Amp outputs.

Buy the Veho Pebble Explorer here from Amazon

Ring RPP950 – two stars

At well over 20cm by 20cm, and weighing in at more than a kilo, this is nowhere near as portable as the other packs here.

But then few other products in the line-up have the internal punch to jump-start a vehicle’s engine if its battery has died. Or power a very intense built-in LED torch.

Naturally, these abilities mean that the internal battery is pretty hefty, making short work of phones, tablets and other gadgets. The trouble is, there are a couple of other heavy-duty battery banks here that are considerably more compact, cheaper, and just as feature-laden.

Buy the Ring RPP950 here from Amazon