Moshi IonSlim 5K Power Bank review

If you’re fed up of power banks that stretch the definition of ‘portable’, you might want to look at Moshi’s IonSlim 5K, which packs a 5,150mAh battery into a case scarcely thicker than a USB port.

The IonSlim is available directly from Moshi for £49.95, which is a bit steep for a battery of that capacity, but you’re paying a premium for the attractive design and minimal form factor. If you’re looking for something cheaper, check out our best power bank deals.

The size is what’s really impressive about the IonSlim and makes it one of the best power banks this year. Measuring just 130x70x8.5mm and weighing 143g, this is smaller and lighter than the average modern smartphone, but similar enough in dimensions that it can happily sit alongside one in a pocket.

The width is what’s really impressive – at 8.5mm it’s only fractionally thicker than the USB-A port – they really couldn’t have made this any thinner without dropping USB-A entirely, so this is about as portable as a power bank gets – matched only by the 7.8mm thick Flux Card.

It’s not only USB-A though – the IonSlim also packs a USB-C port to give you more options, and comes with a USB-A-to-USB-C cable included for easy charging of USB-C devices – though you’ll need to buy a separate Lightning adapter for an iPhone.

Charging is fast too. With 15W power output, you can fill your average smartphone back up to full within an hour or two, and it only takes a bit longer to re-charge the IonSlim itself. Check out our other tips on charging your smartphone faster too.

The 5,150mAh capacity is obviously going to be a sticking point for some. That’s about two full iPhone charges and around one and a half for a typical Android device – that means it’ll cover you for a day, but you can’t carry it around all week without regular top ups.

But then that’s not really how you’re likely to want to use the IonSlim. This isn’t for people who want to pack massive capacity with them, it’s better suited to giving your phone a quick top up while you’re out and about without having to lug around anything bulky. You can always follow our guide to making your phone battery last longer to help.

It helps that beyond the skinny build, the IonSlim is an attractive piece of kit. Dropping the matt black plastic that’s ubiquitous in power banks, this is encased in grey aluminium, giving it a slick, premium finish.

Beyond the USB-A and USB-C ports, there’s a single power button to begin charging your device (there’s no auto-on support here, sadly) and let you know how much charge is left, illustrated through a set of four discreet white LEDs.

The biggest feature the IonSlim is missing is passthrough charging – when you simultaneously charge the power bank and an attached device through a single mains outlet – but given this is firmly designed to be used on the go, it’s not too surprising.

There’s also no carry case included, though this is so slim you’re unlikely to want one too much. The included cable is also very short, at 10cm or so, reinforcing that this is best suited to slipping into the same pocket as your phone.