While many tech buffs will spend more time researching a future purchase than they do using the gadget they eventually buy, sometimes the best pick-ups are the last minute ones.
These last minute grabs are often made to solve an immediate problem, and a common problem for smartphone users is running out of juice in the middle of the day.
If you're an iPhone deployer who leans towards bouts of heavy usage, you may well be familiar with the depleting battery scenario. Thankfully, Mophie's extensive line of on-the-go charging solutions includes cases with integrated backup batteries - Juice Packs, in the manufacturer's parlance. The Juice Pack Plus is well regarded in iPhone circles, despite adding considerable bulk and pushing the weight of an iPhone 4S close to 200g.
The pocket-sized Mophie Juice Pack Reserve is another, more compact option to ensure you don't run out of power at the wrong time. It offers a modest 700mAh battery, far smaller than its stablemate, the Juice Pack Plus, which features a 2,000mAh battery.
However, the Juice Pack Reserve's real strength is its portability - it measures just 80.2 x 40.8 x 16.2mm and weighs only 40g. Those of us who misspent our youth fag in hand will immediately spot how the Reserve resembles a Zippo lighter, complete with flip-off top that reveals a 30-pin connector. In addition to being eminently pocketable, it's also a stylish toy – the rubberised grip feels great in the hand, and the do-gooding RED model looks especially slick.
So where you wouldn't necessarily sport the bulky Juice Pack Plus on a night out, the Reserve effortlessly slides into your pocket - a quick-fix charging solution that will replenish roughly half your battery life, based on our testing. You'll be able to phone in that crucial goodnight call, text the mates you lost earlier on, and then Hailo a cab home - all of which are just as important as picking up emails from your boss.
That said, the Mophie Juice Pack Reserve is not without its downsides. While the USB connector tucks away cleverly into the main frame of the device à la Swiss Army knife, this design can prove fiddly when it comes to charging and lacks the versatility of an extension cord.
Elsewhere, the battery status indicator – activated via a button on the bottom left of the Reserve's body - isn't hugely informative. Where the Mophie Juice Pack Plus features multiple LED lights to indicate various levels of charge, the Reserve offers a single LED that's either green (full), red (less than full), or blank (empty).
We also found the 30-pin iPhone connector to be a bit wiggly when actually plugged into an iPhone. The key ring attachment, which makes the Reserve more convenient for some, snapped off in a worryingly short time. Finally, unlike similar pocket-sized mobile charging solutions, the Reserve can't sync your iDevice while it charges, nor can you flirt with pass-through charging.
All of which makes it amazing that we've fallen in love with the Juice Pack Reserve. Despite an acute recognition of its faults, we found it a genuinely useful iPhone companion for daily use.
The best bit is that, compared to other Mophie gadgets, it's eminently affordable - a mere £30 compared to the £80+ you'd be looking at for a Juice Pack Plus. For professional situations, the Juice Pack Plus is still the only way to go, but the Reserve is a better-than-average sidekick, especially outside of the office. In fact, some pros may even find it a more attractive all round option that its big brother.