Kuxiu is back with a new S3 portable battery that addresses most of the issues I had during my review of the S2, aka the “world’s first” semi-solid state power bank. It also introduces a few new ones, while adding useful features like a kickstand and integrated USB-C cable.

As a reminder, these are not true “solid state power banks” despite the marketing hype. The 10,000mAh Kuxiu S3 uses the same solid-liquid mixed electrolyte found in the S2, making it less prone to thermal runaway than the all-liquid Lithium-ion batteries found in most power banks. Kuxiu says its unique semi-solid state chemistry also lasts twice as long, making it good for about 1,000 charging cycles before the battery capacity drops to 80 percent.

The S3 is more expensive to purchase than other 10,000mAh power banks, typically rated for 300-500 cycles. It lists for $149.98 but is frequently discounted, selling for less than $70 at the time of this writing. At that price, it should be cheaper to own over its longer lifetime.

While it’s easy to discount the safety claim — don’t. In September, Anker issued a recall of 481,000 power banks due to the risk of fire and explosion. And just last week, INIU recalled 210,000 power banks sold on Amazon that were implicated in 11 fires causing over $380,000 in property damage. It’s been a busy year for power bank recalls.

Safety aside, Kuxiu has also fitted the S3 with lots of useful upgrades. In addition to twice the battery capacity, you get a folding metal kickstand, digital display, and detachable USB-C cable that tucks into the perimeter when not in use. You also get faster 30W charging input and Qi2 output up to 25W for devices that support the latest wireless charging standard.

On paper, this all sounds great — and it is — but that larger battery is heavy when used as a MagSafe charger, and it’s far less pocketable. At 106.9 x 71 x 22.15mm (4.20 × 2.79 × 0.87 inches) and a weight of 245.3g (8.65oz), the S3 adds considerable bulk and heft to my 187-gram / 6.6-ounce iPhone 15 Pro. Fortunately, the S3’s stronger array of 18 N52 magnets does a good job of holding everything together and properly aligned for charging.

To test the unit’s 10,000mAh (5,000mAh at 7.7V, or 38.5Wh) rated capacity, I plugged the S3’s integrated USB-C cable into a ChargerLAB POWER-Z C240 power meter, which then slotted into the USB-C jack on my iPhone 15 Pro. I was able to charge the iPhone from 0 to 100 percent once, and then again from 0 to 92 percent before the S3 power bank was empty. I measured 31.12Wh of useful output capacity for 80.83 percent efficiency from the DC/DC circuit, which is typical.

The flat, integrated USB-C cable that tucks into the S3’s perimeter is super useful. Power banks are getting all kinds of unnecessary features these days, but the value of having a cable always at the ready should not be underestimated. While the S3 can’t fully charge my MacBook Pro’s larger battery, it can provide a few extra hours of runtime. The maximum charging speed of the S3 is just 35W, however, which is on par with this class of batteries.

Kuxiu still sells the more portable 5,000mAh S2, which is currently available for $49.99. The bigger S3 currently lists for $68.99 and offers double the battery capacity, a display showing percent remaining, more powerful wired and wireless charging, and the convenience of a kickstand and USB-C cable always available.

Compared to power banks sold by the likes of Anker, EcoFlow, and hundreds of alphabet-soup brands like, um, Kuxiu, the S2 and new S3 semi-solid-state chemistry should be safer and cheaper to own, making them very hard to beat if you’re currently in the market.

Photography by Thomas Ricker / The Verge