infray Hand Warmers Rechargeable, 1-Pack Hand Warmer Reusable 5200mAh Electric Portable Pocket Warmer/Power Bank, Double-Sided Heating USB Hand Heater Great Winter Gift for Women Me

I am finding this device helpful with my cold hands, but as a power bank, I consider it for ’emergency top up’ only — that might be useful one day. Tests confirm its capacity is much lower than the advertised 5200 mAh.

As a hand warmer, using over several days in a variety of situations, one ‘wish’ was that it had a more easily ‘touch’ recognisable button, if it is out of sight and you wish to turn it on/off or increase the level, without having to see it. I found I needed to use a thumb nail to ‘find’ the button and operate it. It warms up fairly quickly (you notice it almost immediately), from 22 degrees (ambient) to 40 degrees in one and a half minutes, 50 degrees in about 3 minutes and started cycling (as described below) from 54 degrees after about 4 and a half minutes, this on the lowest setting.

This arrived in a neat sleeved cardboard box, with USB-C adaptor and USB-C cable, pouch and instruction sheet. It was very discharged, the charge indication LEDs barely glimmered. Charging took a while, initially trickling in at 0.13A for a while, before it eventually ramped up to almost 2A, when it was 2/3 full, it began a slow reduction to zero. I wasn’t timing it, but I’d guess it took over 4 hours in total. The supplied charging cable worked and measures just under 50 cm in length.

Hand Warming use:
Starting from fully charged, in a room at an ambient temperature of 21 degrees Celsius (as all figures below are), the measured temperature results were as follows. In use, the black pads only heated, the white areas are not, although when charging at maximum rate, the bit near the USB-C socket did get slightly warm.

Initially, the lowest heat setting (one red LED) gave a surface temp. of 52 degrees Celsius; this was about as much as my bare hands could tolerate in direct skin contact. This seemed to be constant and equal on both sides. After a while, you do notice it cooling to 38 degrees before heating again to about 50 degrees*, this taking over a minute for each phase. * after 4.5 hours continuous use, it only reached 47 degrees on each cycle, as charge depleted.

The next heat level (two red LEDs lit) gave a surface temp. that varied between a maximum of 57 and then fell to 46 degrees Celsius, before warming again to 57. This cycle repeated, with the heating and cooling phases lasting about 50 seconds each.

At the highest heat level (three red LEDs), gave a surface temp. that varied between a maximum of 64 and then fell to 52 degrees, before warming again to 63. By now the battery level was reporting as being between 33 and 66%, two blue LEDs. The maximum attained fell over successive cycles, retesting the heat levels now gave results of 37 degrees, 56 degrees and 66 degrees. The latter two are too hot for my bare hands but will be useful outdoors when wearing gloves. At any point in time, a double-click on the button changes the LED colour to blue which indicates the battery level remaining.

After 3 hours, most on the maximum setting, it was still providing 56 degrees, despite showing a battery level of between 0 and 33%, I turned it down to lowest level and it remained effective for another 4 hours, after which, it turned itself off. A few hours later, an attempt to turn on was ineffective, as it turned off again after just 2 seconds — so once discharged, it needs recharging, there’s no hope of a little more heat.

Starting charge commenced from 1.6A and grew to almost 2A (as advertised), it seemed to take about an hour for the capacity to reach the 1/3+ level and 45 mins to reach the 2/3+ level. It took somewhat over the 3 hours stated, and absorbed 4300 mAh, well short of the advertised 5200 mAh, but I accept this was only the second cycle after its deep discharge during shipping. When charging is complete, current drops to just 1.5 mA, and the 3 blue LEDs remain lit.

The heat pads are obviously temperature regulated, using it indoors will not drain as much power as using in a colder environment, so we should expect shorter heat periods when used outdoors. This can be offset if the device and your hands are both insulated from the worst of the cold – kept in a pocket, for example. The regulation is loose though, some 10-12 degrees between heating and coasting (cooling).
I have circulatory issues which result in both hands ‘feeling the cold’, however my right hand measures 3 degrees colder than my left. I find that unless the ambient temperature is 23 degrees or more, that right hand especially feels chilly, even indoors.

One aspect I’d personally mark this down for would be its small size, it is much smaller than my “L-XL” hands, measuring 10 cm (4″) long by 5.5 cm (2.2″) wide. For the record, it weighs 135 g. The heat pads are 8.5 cm x 4.8 cm, but that is not to say it is ineffective and the shape and styling is nice. Ideally, I’d have two, one for each hand, as their length is about the width of my palm and the reverse side would warm my fingers and thumb. As it is, I alternate from hand to hand, which leaves the other hand free for tasks.

Power Bank use:
It only has the one USB-C connector, which is why they supply a little adaptor from USB-C to USB-A socket (assuming you don’t lose it), enabling use as a power bank, taking power back out from the same connector used to charge it, unlike traditional power banks. I connected a USB test load to it and set the discharge current to 2A, the stated rating. It supplied 5v up to 0.5A draw, this initially dropped to 4.86v at the 2A and reduced from there with time. I noted that the blue LEDs indicating capacity dropped from 3 to 2 lit within seconds of connecting the load. Voltage had fallen to 4.3v after 25 minutes, still with two LEDs lit. Temporarily reducing load to 1.5A increased the voltage to 4.9v. I set it back to 2A and after an hour and a quarter (75 mins), the charge state had fallen to one LED and the voltage to 3.8v at 2A, it began cutting out and restarting. I reduced the load current to 1.5A and the voltage rose to 4.7v and the second LED lit again for a couple of minutes. I left it running at 1.5A load, which it managed for another 27 minutes before it resumed cutting out as voltage had again reached 3.8v. Reducing the load to 1A gave another 7 minutes before the cutting out happened again. All the while, the one blue LED remained lit. Load reduced to 0.5A (volts back up to 4.9), but it only lasted another 5 minutes. Load reduced to 200 mA, it lasted further 10 minutes, then finally the last blue LED went out and it was dead.

On the second full charge, it gave two blue about 55 mins later after start and finished charging in somewhat over 3 hours, it absorbed 4338 mAh, not much more than the first time. I used it intermittently for hand warming for a couple for days and topped up the charge each afternoon.

The third full charge took 3.5 hours and absorbed 4217 mAh, a bit less than last time. I then left it off overnight and the next day, switched on at the lowest level to see how long it lasted, the listing says “4-8 hours”, I achieved 5.75 hours. The (fourth) charge to replenish absorbed 4232 mAh.

As a backup power bank, it works (as long as you don’t misplace the USB-A adaptor, or only need USB-C), but has runtime limitations, particularly at the full 2A load, although for most users, I doubt this will be a problem at all (as they’ll not be drawing the full 2A).

I note some competitors have a built-in USB-A socket (for similar price), while others come in a two-pack (for about 1.6 times the price of this one). This is not a bad product, hence 4 stars, but other choices might suit your needs better.