ZeroLemon 15,200mAh JuiceBox Battery Charger review

The ZeroLemon JuiceBox is a nicely designed and high-capacity  power bank that can charge up your attached devices at great speed. Also see: Best power banks 2018

Unlike the majority of plastic power banks the ZeroLemon is encased in aircraft-grade grey aluminium, which makes it feel tougher and appear more premium than its £22.99 price would suggest. (That’s via Amazon UK, and the ZeroLemon can also be bought from Amazon.com for $21.99.)

The design is very clean, with the power bank largely clear of the specifications and logos that are frequently plastered over the sides of cheaper models. On one side is the company’s website address in relatively small print, and on the other is its logo.

Nicely rounded edges make the ZeroLemon feel good in the hand, though we should point out that this is a large and reasonably weighty device that is better suited to a bag than a pocket. At 162mm tall it’s a good inch taller than our phone, though roughly the same width, but its slab-like design makes it feel somewhat heavier than it is at 358g. Also see: How to charge your phone’s battery faster

The reason for all this weight, of course, is the amount of juice inside. The ZeroLemon is a 15,200mAh power bank, and the company makes various claims as to how many times it can charge Apple’s (now two generations old) iPhone 6. On the packaging it says it provides 840 percent extra battery for the iPhone 6; on the website it says it can charge an iPhone 6 up to seven times; and further down that same page it says it offers 570 percent extra battery for the iPhone 6. We’d be inclined to believe the latter.

To work out how many times a power bank will charge your phone you simply divide its usable capacity by the battery capacity of your phone. That’s the usable capacity – not the total capacity, since all power banks lose energy through heat generated and voltage conversion. Whereas some power banks can support up to 80- or 90 percent energy efficiency (and where they do their manufacturer shouts about it), the industry standard is in fact between 60- and 70- percent. See all power bank reviews

Given that 8.4 multiplied by 1810mAh (the capacity of the iPhone 6’s battery when new) is 15,204mAh, it is impossible for the ZeroLemon (which has a total capacity of 15,200mAh) to do as it claims.

Without a brand-new iPhone 6 to hand we can’t effectively test ZeroLemon’s claims, though we would hazard a guess that you’ll actually get around five and a half full charges for your iPhone 6. Still, that’s going to get you a lot further than would an iPhone 6 with a dead battery and no mains power supply to hand. Also see: How to improve smartphone battery life

We were disappointed to find the ZeroLemon supports neither passthrough charging (the ability to simultaneously charge it and an attached device) nor auto-on (you must push the power button to begin charging, which also activates the four-LED power status indicators). However, on its side are two full-size USB outputs rated at 3A. These aren’t certified Qualcomm Quick Charge ports, but they might as well be: each can offer up to 15W of power to an attached device, and should the device be able to accommodate all that power it will charge much quicker than it would from a lower-rated power bank.

ZeroLemon doesn’t specify the maximum power output of the device, so we’re not sure whether it can simultaneously support both USB outputs at 3A. Chances are you won’t be connecting two devices able to draw this amount of power at once, however, so each will take only what it needs. Also see: Best MiFi 2016

The Micro-USB input is also pleasingly fast, specified at 2A (or 10W). A fast input is essential for a high-capacity power bank such as this to reduce refuelling times.

Read next: Best desktop chargers 2016.

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