As Li-Ion battery technology improves, we're seeing more mAh in more compact form factors. Compared to the emergency chargers and power banks we had five years ago, at least. The challenge is to take a realistically high amount of capacity with you in a form that you don't notice you're carrying. And the new Lumsing A1 mini scores highly in that regard, presenting just about the most compact way to carry around 6700 mAh, enough for at least two full recharges of a smartphone over 5V USB.

I've previously reviewed both wallet and briefcase chargers, so I can appreciate the compromises in capacity and portability in each design. And the new Lumsing scores pretty well, albeit at a price that won't break the bank. It comes in bare bones packaging, with just a short and simple microUSB to USB lead (though doubtless you'll have your own favourite cables already):

Designed principally for personal use, this compact accessory is finished in textured aluminium and comes with just the one USB output, but it's rated at 2.1A, so is OK for tablets and the most power-hungry smartphones. Do the maths and you'll see that it takes in the order of three hours to charge up from a high current source and then it's yours to carry around as needed:

The single USB port did the job in my tests, though, slightly disconcertingly, the USB jack inside the Lumsing accessory was ever so slightly 'wobbly'. This is probably not important, but I thought it worth noting - for those geeks as OCD as myself!

Note the LED in the photo below, by the way - as per the modern trend, this is a LED torch and is activated by a long press on the main status button, on the side of the power bank. Torch and emergency power functions do seem to go together well, so consider me a fan.

There are four 'quarterly' LED status lights, lit by the button. The A1 Mini is rated at 6700mAh, but as usual, this is at 3.7V, the internal voltage, so we're looking at about 5000mAh delivered at 5V over the supplied (or your own) USB cable to another device, such as a smartphone. This is still a good two complete charges for the average 2015 smartphone, which is more than enough to keep you and your partner (and maybe a kid or two) going on a heavy day out.

The big selling point here is the compactness - see the photo above, where I demonstrate it my average sized hand. The idea is to keep this tucked away in a coat pocket, I think, for emergency top up use (and torch?) in the long winter (this being the Northern Hemisphere!)...

Very decent value and worthy of your consideration - you can find it here on Amazon UK and here on Amazon USA. It's available in black, silver and 'champagne gold'.