Dorset-based Mobile Solar Chargers appeared like a knight in shining armour to loan me two versions of it's portable power-packs to try out.

Aqua Trek 7800mAh
This model is a compact, waterproof, rechargeable power-bank that can fit easily into your pocket. It can be charged directly from the mains, USB, PC or car USB.
The Aqua Trek model featured has a high-capacity “Grade A” Samsung battery with a capacity of 7800mAh, enough to fully charge my mobile phone four times, but there is also a 9000mAh version that will give five charges.
The power-bank is housed in a robust, shock- and dust-proof rubberised body with a USB port cover that needs to be securely closed to give the unit its 1m-depth rating.
This unit is fitted with an integral LED torch that will also flash SOS if the need arises.
The Aqua Trek is compatible with all USB 5V devices including mobiles, GPS, tablets, mp3s, handheld VHF radios and Intova and GoPro cameras.

Travel Solar 6000mAh
The Solar is a robust dual-USB charger with a battery capacity of 6000mAh (three mobile-phone charges). It can be charged from the same sources as the Aqua Trek but also has a solar panel that converts light to trickle-charge the internal polymer lithium-ion batteries.

The solar panel produces 100mAh and can recover up to a single phone charge after a full day in direct sunlight. The Travel Solar isn’t waterproof but does have a rubberised shock- and dust-proof body similar to the Aqua Trek’s.

In Use
I have taken both these models with me on multiple trips overseas. They have worked faultlessly, charging my electronics without
any fuss or bother. They’re compact and unobtrusive, slipping neatly into a pocket or bag, and they seem to hold their charge forever.
I’ve had the Aqua Trek on the deck of an inflatable, getting soaked as the waves crashed over the bow without the slightest hint of a short circuit. I’ve also topped up the Solar model after leaving it on my south-facing balcony all day to catch the sun.
I’ve charged my iPhone, iPad and iPod, and can report that the power-packs took a little longer to fully charge them compared to their generic mains USB chargers.
I’ve also tried to charge an Intova Sport compact video camera that I had on test, hoping to get enough power back into its batteries between dives, but alas a mere hour’s surface interval was insufficient to provide enough of a charge for the camera to be used for more than a few minutes.

Both of these mobile battery-chargers are beautifully constructed, work faultlessly and are small and light enough to be truly portable. Here, however, is the rub. Try as I might, I couldn’t find a real-world use for these power-packs, especially from a diver’s perspective.
I tested them by charging my devices, but
I didn’t “need” to do so. I didn’t actually find myself in a situation in which they were the only power sources available.
Everywhere I’ve ever stayed had mains electricity. Even on remote island retreats, there were plentiful two-pin sockets supplying 110V to charge everything I had taken with me.
The liveaboards from which I’ve dived have more charging sockets than you could need – all my electrical gear gets charged overnight while I sleep, giving a full day’s use before I need to do it again.
I can see lots of instances in which I would benefit from having these hi-tec devices available, but unfortunately they have nothing to do with diving, and this is, after all, a review for diver.
If I was back-packing, camping or trekking to some remote outpost I doubt if I would leave home without one. As a travelling diver I’d rather pack an extra T-shirt and use the plentiful mains charging facilities I’ve found wherever I go.
Now that I’ve said that, Murphy’s law dictates that next time I travel I’m going to be stuck on a deserted island in the middle of nowhere with a flat phone battery when I need to call for emergency assistance. Perhaps I should sacrifice that T-shirt and take an Aqua Trek just in case?

PRICE £44.95
BATTERY Samsung high-performance, 7800mAh capacity
BATTERY LIFE Minimum 500 full charges / discharges
CHARGE TIME 7hr (mains charger)
Diver Rating 7/10 

PRICE £34.95
BATTERY Polymer lithium-ion 6000mAh
BATTERY LIFE Minimum 500 full charges / discharges
INPUT Micro USB, 5V DC /1000mAh
OUTPUT 2 x USB 5V/1A and 5v/2.1mAh
CHARGE TIME (Mains) 5hr
CHARGE TIME (Solar) 45hr in direct sunlight
Diver Rating 7/10