Review of the 'SMARTCOBY ULTRA SLIM 3K,' an ultra-thin and lightweight mobile battery that can be attached to the back of your smartphone for charging.



Osaka-based digital equipment manufacturer

CIO released the ' SMARTCOBY ULTRA SLIM 3K ' mobile battery in January 2026, touting it as 'one of the world's thinnest mobile batteries.' Its design makes it compact for both carrying and charging. I was looking for a mobile battery that was easy to carry around, and CIO's new product seemed promising, so I requested a review and had them send a unit to the editorial department. I then tried out the SMARTCOBY ULTRA SLIM 3K.

SMARTCOBY ULTRA SLIM 3K | CIO Co., Ltd. Official Website - Charger & Mobile Battery Manufacturer
https://connectinternationalone.co.jp/cioproduct/mobilebattery/smartcoby/cio-mb10w1c-3k-uswl7/

The packaging for the SMARTCOBY ULTRA SLIM 3K.



The contents include the SMARTCOBY ULTRA SLIM 3K unit, a USB-C charging cable, and instruction manuals.



The SMARTCOBY ULTRA SLIM 3K comes in two colors, silver and black, and the one we'll be using is black. The SMARTCOBY ULTRA SLIM 3K has a battery capacity of 3000mAh/3.88V, which is 11.64Wh.



Holding it in your hand really highlights how compact the SMARTCOBY ULTRA SLIM 3K is.



The SMARTCOBY ULTRA SLIM 3K measures approximately 104mm in height and 70mm in width. Here's a comparison with the iPhone 16, which measures 147.6mm in height and 71.6mm in width.



Furthermore, the SMARTCOBY ULTRA SLIM 3K is characterized by its ultra-thin design, measuring approximately 4.98mm thick. Here's how it compares to the iPhone 16, which is 7.8mm thick.



The actual weight of the SMARTCOBY ULTRA SLIM 3K is 84g.



The right side contains information such as the authentication number.



There is nothing special on the top and left side.



The bottom of the device has a power button, a USB-C port, and an indicator light.



The back looks like this.



To begin using the SMARTCOBY ULTRA SLIM 3K, first press the power button and confirm that the indicator light illuminates.



You can charge your smartphone by connecting it with a USB cable. The charging time is up to 150 minutes, and the output using the included USB-C cable is 5V x 2A, for a maximum of 10W.



Furthermore, if your smartphone supports Qi wireless charging, you can charge it simply by attaching it to the back. Below is a picture of the SMARTCOBY ULTRA SLIM 3K attached to an iPhone 16; it sticks on with a magnet. The Qi wireless charging output is a maximum of 7.5W.



Below is a picture of an iPhone 16 being held in the hand with the SMARTCOBY ULTRA SLIM 3K attached. Because the SMARTCOBY ULTRA SLIM 3K is quite thin, it's easy to operate the phone while charging.



Furthermore, the SMARTCOBY ULTRA SLIM 3K has a built-in anti-loss tag that is compatible with the iPhone's '

Find My ' feature. The 'Find My' function is said to work for about two months even if the mobile battery is depleted, so it will be useful if you misplace it somewhere. To register it with 'Find My,' first press and hold the power button until you hear a 'beep' sound.



Open the 'Find My' app on your iPhone and tap 'Add Item'.



Select 'Other items that can be brought'.



Since 'CIO-MB10W1C-3K-USWL7' is displayed, tap 'Connect'.



The location and address of the SMARTCOBY ULTRA SLIM 3K on the map are displayed.



The SMARTCOBY ULTRA SLIM 3K has a capacity of 3000mAh, which is roughly enough to charge an iPhone 16 about 0.4 times, an iPhone 15 about 0.5 times, and an iPhone Air about 0.55 times wirelessly. It's not suitable for repeated, full-charges, but it's incredibly convenient for everyday use, being lightweight and slim for quick charges. For those who find their smartphone battery is sometimes just a little low, this compact mobile battery is a very useful option.

The SMARTCOBY ULTRA SLIM 3K is available on Amazon.co.jp for ¥8,980 (tax included).

Amazon.co.jp: CIO Ultra-thin Mobile Battery [4.98mm] MagSafe compatible Qi Wireless Charging 7.5W 3000mAh Lightweight [approx. 82g] Find My compatible Anti-loss SMARTCOBY ULTRA SLIM 3K Compatible with iPhone 12 / 13 / 14 / 15 / 16 / 17 / Air series: Computers & Peripherals



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in Hardware,   Review, Posted by log1e_dh