Now this is a rugged power bank that looks like it means business. The EasyAcc Rugged Power Bank is as useful as it is tough - find out more in our EasyAcc 20,000mAh power bank review. Also see: Best power banks 2016.

EasyAcc’s Rugged Power Bank has three aces up its sleeve:

1. Its high-capacity. Rated at 20,000mAh, and with an industry average of 65- to 70 percent efficiency, you should see at least 14,000mAh from this device for charging your USB-connected phone, tablet or other device. That would fill a Samsung Galaxy S7 nearly five times, and an iPhone 6s eight times.

2. Its tough design. The EasyAcc Rugged Power Bank has IP67 certification, which means it is totally protected against dust, shock and water - provided you keep its port cover closed. Also see: Best MiFi 2016.

3. Its price. This power bank may lack some features of its high-end rivals, but just £33.99 from Amazon UK (or $49.99 from Amazon US) is a great price for a rugged power bank with this capacity.

The EasyAcc’s unique industrial design really appeals. It’s a large green rectangular plastic slab, protected with a arrow-patterned black jacket that’s bolted into place. At one end is an LED flashlight that is big enough to actually be useful when you’re out in the great outdoors; it cycles three modes: constant, flash and SOS.

And that’s sort of the point of a power bank: they come into their own when you are away from mains power and unable to charge your smartphone or other USB-connected devices, such as a tablet or GPS device. You’re more likely to have need to call on one when you’re in the middle nowhere than you are anywhere else, so it makes sense to build in protection from the elements and enough capacity to keep you ticking over several days.

To the side of the flashlight is a plastic port cover that you pinch to release. A rubber seal ensures dust and water are kept out of the EasyAcc’s two USB- and single Micro-USB ports, while a second piece of rubber tethers it to the bank. This is essential, since the second you lose the port cover the device loses its IP67 protection. (Note that it’s protected from the elements only when it’s not in use, since attaching a USB cable will prevent the cover closing.)Also see: Best desktop chargers 2016.

This isn’t the first rugged power bank we’ve tested. There’s also the smaller and slightly cheaper 10,400mAh SandBerg Outdoor PowerBank, from which we’ve already managed to rip off the rubber seal protecting the ports, and the more expensive 15,000mAh, IP66-ratedLimeFuel Rugged L150XR power bank, with which we’ve experienced issues in re-charging via the Micro-USB port. Of the three, this EasyAcc is easily our favourite.

In common with this EasyAcc the LimeFuel offers two USB outputs, and both are rated at 2.4A (12W). However, the device can support a maximum output of only 4.2A (21W), which means with two devices plugged in the most either can reach is 10.5W. Things are simpler with the EasyAcc Rugged Power Bank: one port is rated at 2.4A (12W), which will accommodate tablets and phones that can accept a fast input; the other is rated at 1A (5W) and suited to smaller devices such as smartphones and GPS gadgets. You can plug any device into the faster output without harming its battery, but some tablets (particularly iPads) may be fussy with the slower output. Also see: How to improve smartphone battery life.

Our only issue with these ports is that there’s no way of knowing which way around they go without reading the specification on the rear of the device and then matching it up with the output labelled Output1 or Output2 (with no space - we’re not sure which is more annoying). It would have been better if EasyAcc had labelled these ports with their output rather than giving them a meaningless name.

When you need to charge up your phone or other device you simply plug it in and press the button on the front of the device. This button is also used to turn on (or off) the flashlight with a double-press, and once it’s on you cycle through the modes with a single press. The EasyAcc will automatically turn itself off 30 seconds after the device has finished charging or is detached from the bank.

Four blue LEDs (two sit either side of the button) are used to show you how much power remains in the bank. With power banks of this capacity we usually prefer to see LCDs that give an accurate readout, because the 5,000mAh jump from LED to LED is enough power to charge an iPhone twice. Of course, LCDs add to the price, and one of the things we like about the EasyAcc is its good value.

The EasyAcc does not support passthrough charging, which is a pain. With such a high capacity it will take some time to refill its own battery, and it would be useful to be able to charge both it and your phone without taking up multiple wall outlets on your return home. It’s good to see the Micro-USB input is rated at 2A (10W), however, and it will charge relatively fast given a compatible adaptor.