BMX SolidSafe power banks review: thinner, safer, and built for travel

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The BMX SolidSafe range combines semi-solid-state battery technology with Qi2 charging, premium materials and surprisingly slim designs. The Air 5K is the headline act, but the larger models may make more sense for everyday use.

Power banks aren't normally a particularly exciting category. Capacity is limited by airline regulations, charging might get a bit faster, and cases get thinner, but short of occasionally sticking a screen on one most portable batteries have been using broadly the same internal tech for years.

BMX is trying something rather more interesting with its SolidSafe range. These magnetic power banks use semi-solid-state cells, which contain considerably less liquid electrolyte than conventional lithium-ion batteries.

This is said to improve thermal stability and it'll reduce the risk of swelling, overheating and fire.

BMX SolidSafe Air 5K: the one that's getting the headlines

The £59.99 Air 5K is easily the most interesting of the three. It holds 5,000mAh, supports 15W Qi2 magnetic charging and up to 20W over USB-C, but the remarkable bit is the thickness - it's just 6.8mm at its thinnest point.

That qualification matters because the charging area itself sits slightly proud, but it's still absurdly thin for a magnetic power bank.

Let's get something straight, a 5,000mAh power bank isn't going to keep you off-grid for a weekend. Instead it's there to rescue your phone halfway through a long day without forcing you to carry around a battery resembling a house brick.

The titanium outer shell helps too. I like the feel and rigidity of it, and the whole thing comes across as considerably more premium than the plastic battery packs I've accumulated in drawers over the years.

The compromise is features. You don't get the colour display found on the other SolidSafe models. Four LEDs give you a rough idea of remaining capacity, and that's about it.

Charging the battery itself is limited to 15W too, which isn't especially quick by modern standards.

If your priority is having a battery slim enough that you'll actually carry it every day, this looks like the standout model in the range.

BMX SolidSafe 5K: probably the sensible choice

The standard SolidSafe 5K takes the same basic 5,000mAh idea and sacrifices some of the Air's spectacular thinness in exchange for more useful everyday features.

It's around 11.7mm thick and uses aluminium rather than titanium, but you gain a full-colour display showing remaining battery percentage and live charging wattage.

There's also a built-in USB-C cable that doubles as a lanyard. That might sound like a tiny thing, but I'm a big fan of power banks that don't require me to remember another cable. If you're carrying emergency power, it seems rather sensible to carry the means of getting that power into your phone as well.

Qi2 wireless charging still tops out at 15W, while USB-C output reaches 20W.

Capacity is perhaps the key stumbling block here, especially for the £59.99 price. A 5,000mAh internal battery does not mean 5,000mAh will arrive inside your phone. Conversion losses are unavoidable, and wireless charging wastes even more energy as heat.

That's not uniquely a BMX problem, but anyone expecting one of these little batteries to completely refill a modern flagship smartphone may come away disappointed.

I'd treat the 5K as a substantial emergency top-up rather than another complete phone battery.

BMX SolidSafe 10K: the one I'd take travelling

If you're less concerned about thinness and more interested in making it through a couple of long days, the SolidSafe 10K looks like the sweet spot.

As the name suggests, capacity doubles to 10,000mAh. It also raises wired output to 30W, adds a second USB-C connection and can charge three devices at once using the two wired connections and Qi2 wireless charging.

At 18.9mm thick and 230g, though, you're firmly back into conventional power-bank dimensions. Nobody is going to mistake this for the Air.

What you're getting instead is flexibility. There's enough capacity for around two phone charges, depending on the handset and how you charge it.

At £79.99, it also doesn't command an enormous premium over the two 5K models. For travelling, that would probably be my choice.