The technology behind rechargeable heated jackets

The technology behind rechargeable heated jackets


As early as 1912, physician Sidney Russell invented what could be called the world’s first electric under-mattress heated blanket – a concept that would later be developed into a practical, thermostatically controlled blanket by prolific inventor George Crowley in 1930. Crowley adored his invention and one remained on his own bed even after he passed away in January 2000, remaining in regular use by his wife.

Once Crowley had put the finishing touches on what would become the first modern electric blanket it became only a matter of time before the combination of fabric and active electric heating would make its way to apparel. In 2001 the North Face MET5 became the first electric heated jacket available for sale – a pioneer of the technology, MET5 was selected by TIME as one of their best Inventions of 2001, however, as with many trail-blazing products, it was burdened with an obstructive $500 price-tag.

Other major brands have entered and departed the heated jacket arena since with differing degrees of success, largely tentatively, with rechargeable heated jackets developed as projects aside to proven and established clothing and outdoor wear collections. In recent years, however, new products have found success in the market thanks to revolutionary improvements in fabric heating technology and reliability – these next-generation jackets are created by brands such as 8K with stylish, versatile heated jackets the sole focus of their attention, which should come as no surprise, as for a heated jacket to become your everyday jacket, it must also be a brand’s everyday product.


Much like George Crowley’s electric blanket, 8K Flexwarm jackets are loved and used regularly by the people behind them, with the latest collection of revolutionary heated apparel for women and men arriving in Autumn 2018.


Many of the heated apparel products currently in circulation use carbon fibre heating technology, which has been used for some time, carbon fibre can be found in many heated jackets going back several years. As carbon fibre is the most common technology available, it’s currently the best standard for comparison to the Flexwarm® heating technology found in 8K Apparel.


Comfort & Heat Distribution

Carbon fibre heated clothing works using strips or tubular heating elements, like wires, that are spaced across the heated areas of the jacket to provide warmth.

While these elements are flexible to allow the user normal movement, they are more rigid than the apparel itself so do reduce flexibility. As the jacket heats up, areas directly in contact with these narrow strips will naturally be hotter than any areas in between – this means the temperature is fundamentally uneven and must spread outwards from each source, losing energy in the process.

Flexwarm® uses an ultra-thin film layer as a heating element, allowing the jacket to flex and move with you as normal to retain the level of comfort you’d expect from high-quality apparel. This layer provides a uniform source of heat that’s flush to the fabric and heated throughout, rather than relying on heat to spread from narrow, individual elements – this means warmth can be passed directly through the fabric efficiently and effectively without any uneven hot or cool spots and eliminating the need for excessive layering.

Heating Time

When the thermometer has fallen below zero and you need to head out, you brace yourself for the cold – you know that it’s going to take a little time for your body to come to terms with the change in temperature, so you want your jacket to heat up, and heat up fast. In testing, Flexwarm reached 40-50 degrees up to 3 times faster than carbon fibre.

Flexwarm® technology reached 50°C / 122°F in just 360 seconds, in comparison carbon fibre, took 16 and 37 minutes respectively – In context, if you’re taking the dog for a walk wearing a carbon fibre jacket, you’ll reach a comfortable temperature just in time to walk back into the house and take off your coat. Flexwarm® technology, on the other hand, will have you nice and toasty in no time.


The Perfect Temperature

Carbon Fibre’s uneven heating makes it very difficult to assess when the jacket is at the correct temperature, as some areas won’t quite have warmed up yet while others may be at risk of getting too hot – these jackets usually have vague controls such as low, medium & high – you wouldn’t settle for this on your thermostat at home, so don’t compromise when it comes to a heated jacket.

Flexwarm® technology puts you in control of exactly how much heat you want from your jacket, and thanks to the even heat distribution Flexwarm® technology provides, a Flexwarm® heated jacket can climb to a specific temperature and then retain that temperature as required without any areas exceeding it, or not quite reaching it before the cut-off.

Energy Efficiency

Heated jackets require a portable power source, so many include a removable power bank. A power bank adds smartphone-charging functionality but has a limited volume of energy to work with. This makes energy-efficiency incredibly important for keeping the cold out, your phone charged and avoiding the additional burden of constant recharging.


For a heated jacket to remain lightweight and comfortable it needs to strike the correct balance between the power storage, size and weight of its power bank, so simply adding a larger battery would simply add weight – making the jacket lopsided and cumbersome. 8k Flexwarm jackets are efficiently designed to use a lightweight 5V power bank, whereas carbon fibre jackets usually require at least 7V – this means 8k Flexwarm jackets use less power despite heating faster and more evenly than carbon fibre counterparts.

Also, the less precise heating settings on a carbon fibre jacket (low, medium, high) mean that the jacket can’t distinguish a precise temperature, whereas Flexwarm® technology uniformly heats to the exact temperature you’ve chosen and then controls the power input so as not to exceed it or fall below it. 

Machine Washing

Outerwear needs to offer durability, your jacket regularly takes a beating from the elements, whether it’s rain showers, wind, snow or sleet, nature leaves a mark. So, you need to be able to safely wash your heated jacket without worrying about destroying the heating elements. In testing, we found that carbon fibre wire heating performance diminished after 28 washes and ultimately failed after 40 washes. Flexwarm® technology exceeded the testing and continued to perform correctly beyond 50 washes.


Stay Connected

One of the truly groundbreaking capabilities of Flexwarm® is the ability to embed Bluetooth, delivering the unique capability of providing real-time temperature data that can then be controlled via the Powered by Flexwarm app. 8K Heated Apparel has been designed to harness this feature, designing a range of outerwear that pushes the boundaries of wearable technology in fashion and  creating a truly unique experience when worn.


 You can watch the  8K Flexwarm revolutionary heated jackets in action here

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