A smartphone battery charge never lasts long as you really need. While the modern handset is packed with features, they all consumer energy and, as a result, poor battery life is one of the downsides to most smartphones on the market today. Some models have replaceable batteries, which is great, but if you’re one of the many millions of iPhone owners out there, that just hasn’t been a possibility.

While Apple themselves have always tried to tell us that the batteries are more than adequate (I personally get around 14-16 hours of use out of my iPhone on average) they now offer their own battery case, which is neither particularly good value or even close to being attractive. Fortunately, a phalanx of third-party manufacturers are ready to step in with suitable accessories.

One of them is Phinexi, that produces a range of smartphone battery cases, supporting the Apple iPhone 6/6s and iPhone 7. While battery cases are generally thicker than you’d desire, these new models are slimmer than most, if not all, competitors available on the market today.

The case provides an additional 2600 mAh of additional battery power in a form factor that is just 3.8mm deep and 2 mm thicker than the iPhone itself. Considering that the standard iPhone 6s battery capacity is only 1810 mAh, this gives your phone an additional 140% of power – an impressive feat considering it weighs just 68 grams.

It’s attractive too. I have had a couple of different battery cases over the years. They have all worked well but added bulk and somewhat spoiled the lines of an otherwise good-looking phone. This battery case is attractive and could easily pass for a standard case.

The integrated battery is fully encased in silicon and stretches to the bottom and both sides of the case. The grippy silicon outer ensures the phone is far less slippery than naked, so you should have a solid grip on the handset at all times. The outside silicon edge has sealed buttons for volume and power, with cut outs for the mute/rotation switch and speaker/headphone socket. Meanwhile, the rear of the battery case includes a cut-out for the camera lens and flash.

As an additional feature, the bottom of case has a heart-shaped button which, when pressed, illuminates a series of LEDs showing you the charge status of the battery. Depressing this button for more than a second will turn on the battery – you will hear a tone to confirm charging has begun.  These lights remain lit while they are charging the phone, extinguishing as the available power is depleted.

Now with the majority of third-party chargers, power is connected via a USB cable. In truth, this isn’t really a problem at home as most will have spare cables lying about from a plethora of other devices – but it is another cable to have to remember to pack when away from home. The beauty of the Phinexi case is that it charges using a standard Lightning cable that comes with each and every iPhone. Not only does this port allow you to charge the iPhone and case simultaneously, but as a first, it also allows you to sync data on the phone too. So, you don’t actually need to ever remove the phone from the case.  Charging both the phone and the case completes in under three hours and it’s claimed that the case can fully charge your phone (on its own) in around 45 minutes.

As stated, I think the design of the case is great. Vitally, it doesn’t detract from the design of the iPhone too much and offers much-needed protection.  In use, the top of the handset is exposed, to make inserting and removing the phone as easy as possible. There is, therefore, a small risk of damage due to that top edge being exposed, but given how awkward some cases can be to work with, you’ll have the benefit of added convenience.

It’s a slight shame that there isn’t more of a lip on the front of the case to give a little bit of extra protection to the screen when it’s laying down flat. But, many of us choose to use a screen protector and Phinexi do, in fact, sell their own screen protector which would help with this problem.

So, the case looks great on the phone and adds protection without bulk. But how is the performance?  Well, the battery performance is fantastic. The case charges as quickly as promised and syncing runs seamlessly whilst using the phone. With the battery case in place I could get well over a day’s heavy usage out of the phone and when being used sparingly, battery life would stretch easily to two days.  I was pleasantly surprised at how much additional juice such a slim battery could provide.

I should note that Phinexi had sent me an earlier version of their battery case that had a number of performance issues. Following feedback, they sharpened their pencils and came back with a case that, in my opinion, looks better than the original and, more importantly, performs as it should.  Kudos should be given to Phinexi, as not every manufacturer would or could make such wholesale improvements in such as short space of time. Be sure, however, you purchase the latest generation of their case, however, for best performance.

With the iPhone 6/6s maintaining considerable popularity, the Phinexi Battery Case has a large user base to go after, but they have also introduced a case for the iPhone 7 too. As I have recently upgraded to an iPhone 7, I will be looking at one of these myself.  The Phinexi Battery Cases are currently priced at £44.99 and £49.99 respectively.