Power banks? Flashlights? Long life hand warmers? Oh yes!

I have to say that I wasn't expecting much from these, the Boiros 4-in-one rechargeable hand warmers, not least because the packaging was Chinese-generic and Boiros name was implemented in a couple of cheap stickers. However, the actual product is well made and works rather splendidly. Not least because of the potential for being tiny emergency power banks as well.

Note that in all the photos here, the refresh rate of the LCD displays is too slow for the camera shutter speed, so not all segments are shown in the images. But they're fine to the eye!

The units are charged (both at once via a single 'Y' cable, unusually) by USB Type C at 10W and a full charge takes 90 minutes or so from any Type C source you happen to have around. Output, if you want to use them as power banks, is via USB-A and also at 10W. But that's OK for emergency use, I suspect, especially with this lowest common denominator port.

The idea with these warmers is to use a couple of meaty power bank-grade Li-Ion cells to discharge through one or two heating elements per 'hand', giving a genuine full day of use, surprisingly. As a physicist, I'd have guessed that generating heat would deplete the small cells rather quickly, but it seems as if this isn't the case.

Giving, again, a surprising amount of flexibility, are 8 different heating settings per unit. So 4 settings for two heating elements, one in the front of each unit, one in the back. These correspond to target temperatures in Centigrade, so ('High' being double sided, 'Low' being single sided):

• H1/L1:38-42°C
• H2/L2:43-46°C
• H3/L3:47-50°C
• H4/L4:51-55°C

In practice, if you're going to grip these things 'bare', then the '3' settings are just too hot for comfort, but I think '3' and '4' might be more for inserting inside something else or an item of clothing. I did some benchmarking tests against the marketing claims (e.g. 12 hours for L2) and found that the warmers matched the numbers across the board. So yes, L2 (level 2, single sided) heat lasted for over 12 hours straight. Obviously, if you fire up both heating elements at level 2 then you're looking at six hours continuous output. 

Setting the heat level, firing up the torch (not very bright, but OK for finding keys or a lock or similar), or just seeing the current battery status, are all done through multiple and long presses of the two buttons on each unit, as shown, and it's all explained well in the paper instruction manual.

Before passing judgement on the warming functions, I wanted to comment on the power bank aspect. Although probably best left for emergency use because of the 10W output limit (per unit), having 7000mAh on tap in such a small pocket-friendly gadget is worth noting. Or 14000mAh if you have both units with you. That's enough to recharge several smartphones, even if not at lightning speed. They'll get you home, etc.

These hand warmers do - absolutely - work as advertised, but their worth depends on the use case. Because if your fingers are wrapped around a warmer unit then you can't do much else with that hand. The ideal use case is standing around in the freezing cold watching a kid's football game, that sort of thing, where you're having to be in a cold environment and just trying to keep your hands from going numb.

An intermediate use case would be, for example in my case, walking the dog in winter, where one hand is having to hold the lead and the other potentially either (temporarily) holding used poo bags or taking a phone call. Juggling hand warmers here would be more trouble than it's worth and (simply) good gloves would be better.

The marketing material shows skiers and hikers, but wouldn't those activities involve holding poles of some kind? 

So the actual effectiveness of pill-shaped hand warmers depends very much on why you want them - and we're all different. In practice, I end up keeping them in my coat pockets, so that I can get a hand blast/recharge whenever I feel the need, plus some of the warmth makes its way into my clothing, which also helps.

What I can say is that these work as advertised, are very well made (albeit in plastic), and have decent emergency power bank and flashlight functions. I see some negative reviews on Amazon, but my experience has been all positive.

I bought these at £32, which seems a good price, but like most Chinese-made products from brands you haven't heard of, prices do fluctuate, so your mileage may vary here.

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