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Hotronic S4 Boot Heater Review

Hotronic S4 Boot Heater Review

Posted On 31/01/2021

Hotronic S4 Boot Heater review: If you have a problem with cold feet while having sports activities in the winter and you are looking for a high-quality boot heater to heat up your feet, then the Hotronic S4 Boot Heater is the right solution for your problem. Hotronic S4 Boot Heater is one of the top heaters that you can find on the market today and can be used almost in every footwear.

Our Verdict

As a top model from Hotronic brand, the Hotronic S4 boot heater has all great features that belong to one product of the highest class, including 4 different modes for heating, an incredible 178 F temperature of heating when it is set at the highest setting (84 F is the lowest temperature of heating at the lowest mode of heating), 21 hours non-stop heating on the lowest setting, the heater can be installed in any kind of footwear, also very important is that the insoles that come with these heaters can be easily customized to any foot shape and size and other more special useful features!

Hotronic S4 Boot Heater Review


The Main Differences between Hotronic S4 Universal and S4 Custom

The S4 Ski Boot heater is available in two variants: Custom and Universal. The two variants of the S4 model are completely identical in design and performance, the only difference between the two packs is that the Custom model does not come with a universal insole.

In fact, the custom variant is intended for people who want to install the heating element on their own custom footbeds or orthopedic insoles themselves.

While in the Universal S4 variant you will get all the elements and accessories you need to successfully install a boot heater in any ski boots or winter shoes. The Universal S4 comes with a universal insole so you can replace the insole with the one at the bottom inside the ski boot.

Otherwise, both variants of the S4 offer you a pair of heating elements, covers, battery and heater connectors, battery packs, and also a battery charger. You have exactly what you need for installing heaters in your ski boots.

Watch the Video Hotronic S4 Universal vs. Hotronic S4 Custom

The Heating Elements

The main task of heating in the S4 system is performed by ultra-thin heating elements. Their design is in the form of circular discs with thin charging wires attached to them. Each one of these heating elements will need to be placed into the insole of your boots (or in the universal insole that you will get in the Universal S4 package).

The small dimensions of the heating elements allow them to fit comfortably in any insole or footbed. But keep in mind that these heaters are only compatible with adult sizes. There are two most convenient places to be placed these elements such as the ball of the foot and just below the toes.

One of the sides of the heating element is with a sticky coating. This allows it to be securely attached to any insole or footbed. The circular shape of the heating elements allows heat to be easily transferred to a wider area of your foot.


Hotronic S4 Liners and Covers

Once you place the heating elements on the insole, now you need to cover the elements with a piece specifically designed for that purpose so-called liners or simply covers.

These covers are made of a special material called Cambrelle. Cambrelle is a synthetic fiber that has a great ability to absorb sweat and is very durable, it is mostly used as a material for lining for running, skiing, hiking and climbing boots. This is the main reason why Hotronic decided to use this material on their products.

This non-wool Cambrelle material is made from a double layer of nylon fiber and is the standard for the production of high-quality liners for outdoor boots and shoes. As I said, these Cambrelle liners have superior properties when it comes to moisture handling. Their way of working is that when you wear boots or shoes these liners absorb sweat from the skin on your feet, this way your feet stay dry and you feel comfortable. Simply, the moment you remove your boots, the moisture dries out of the liners.

The Cambrelle covers of the Hotronic S4 are designed to fit nicely when mounted on the insole and heating element. On the underside, the covers are sticky, allowing you to quickly and easily attach them to the insoles and heating elements.

The shape of these liners is the same as the shape of the insoles only that their dimensions are several sizes larger. This is a very useful thing because once you attach the covers to the insoles; it allows you to ideally shape them to your feet by cutting off the excess edges. Although the heating element does not cover the entire foot, the liner is capable of transmitting heat evenly to your feet.


Hotronic S4 Universal Insoles

These soft Hotronic insoles you will not get if you buy the custom package, they are coming only with the Hotronic S4 Universal. Their colors are red and are specifically designed to be used with wires and heating elements only. By using these universal insoles, you will have no need for trimming to shape them into the shape of the existing insoles in your footwear.

For making these insoles is used EVA foam, which gives softness to these compact insoles that weigh only 3 ounces (about 85 grams). These insoles are “one-size fit all design”, which means they will be too big for some sizes of boots and shoes. But that shouldn’t be a problem; you just have to trim off the excess to the ideal size of your feet.


Hotronic S4 Battery Packs

Same as the insoles, you will get a pair of battery packs. From the heating elements come out flat wires leading to the battery packs. Usually, in each boot is inserted one heating element and connected to one battery pack that is mounted on the boot.

This S4 battery pack is designed to be easily attached to the side of the boot or to the back of the boot using clips. S4 battery packs can be recharged and they use NiMH cells which are much safer to use than batteries using Li-ion and Li-po cells.

Also, NiMH cell batteries are better for use in cold weather, but especially in winter. This is one of the many reasons why NiMH cell batteries are especially used in winter footwear.

Another positive thing about NiMH batteries is that you can recharge them at any time without having to wait for them to fully discharge, and yet their capacity will not be reduced at all, as it is often the case with NiCad batteries.

Watch the Video How You Can Install the Hotronic Slide Strap Bracket


Multiple Heat Settings

Like many of the top heating systems used to heat clothing and footwear, the Hotronic S4 features adjustable multiple heat settings. Instead of three different temperature settings found in most heating systems commonly used in heated boots, heated socks, heated gloves and other types of heated clothing, this Hotronic S4 has an additional heating setting. Here is an overview of the four heating settings:

  • Level 1: is a temperature from 84 to 98 Fahrenheit degrees
  • Level 2: starts from 107 to 121 Fahrenheit degrees
  • Level 3: is from 122 to 138 Fahrenheit a degree
  • Level 4: it gives you a short burst of high temperature which is between 158 and 173 Fahrenheit degrees. This setting usually is used when you need an extra amount of heat to your feet in extremely cold weather. Level 4 will be activated periodically in intervals of 3 minutes. Also, you have an option to set the Level 4 to deliver a continuous heat, but you need to be very cautious to don’t get burned.

As you can see the heating system offered by the Hotronic S4 is more than enough to use in the most demanding winter conditions.


Hotronic S4 Temperature Management

For easier temperature management, the controls on this heating system are on top of the battery packs.

In fact, these are just two buttons, and between them is a series of 4 red LEDs in line. Each line shows you the current level of heating. They also tell you whether the heating system is on or off. These red LEDs are visible even in low visibility conditions.

By pressing these buttons you can easily adjust the temperature of your feet. One more thing you need to know about these red LEDs is that when you set the heating system to Level 4 to deliver continuous heating instead of short bursts, the LEDs will flash as a warning.


Hotronic S4 Battery Performance

It is normal that the battery performance of any heating system with adjustable heat settings is closely related to the way it is used. For example, if the system operates at the highest heating mode, it is obvious that the battery will have a shorter life than normal.

Below is an estimate of the battery life with NiMH cells in a Hotronic S4 heater in different heating modes.

  • Level 1: in this level, the battery life should be between 16 and 21 hours
  • Level 2: in this mode, the battery life is should be between 7 and 10 hours
  • Level 3: the average battery life is about between 5 and 7 hours
  • Level 4: and in the highest mode it will be from 2 to 4 hours

With controlled use, the batteries of this S4 Ski Boot Heater can warm your feet all day long which is truly impressive. Even more interesting is that the S4’s batteries are capable of delivering heat for more than a day to almost two days if set to work in the lowest mode.

Another thing, even after a few winter seasons of use, the capacity of these batteries still will be over 90 percent of their original capacity. This is another sign of the quality of the batteries that are built-in the Hotronic’s S4 boots heater.


Hotronic S4 Comes with Universal Charger

You will also get a high-quality charger along with this heating system. This charger has two sockets, one of them can be used for plugging into the US-style of sockets and the other one is for the European style of sockets. Another positive feature is that this charger has two connectors that allow you to charge both batteries at the same time.


The Installation of the Hotronic S4 Boot Heater

So, Hotronic’s S4 Heating System is really easy to install. It can be done at your local ski shop or you can even do it yourself if you have a little bit of time. All you need are basic supplies like a roll of duct tape and razor blades.

Some of the ski boots already have the slits and straps in place for installing a heating system. So you can just easily remove the current insoles of the boots and place the insoles of the Hotronic S4. Now attach the battery packs on the boots, and then insert the cables of the heating elements through the slits to connect them with the battery packs.

Even if the ski boots don’t have slits and straps, to integrate this heating system is still an easy job. Also, there are some YouTube videos on how to install the Hotronic S4 ski boot heaters where they are explaining the whole process.

Watch the Video How You Can Install the Hotronic S4 Custom


You Will Really Enjoy Skiing with This Boots Heater

The Hotronic S4 boot heater is not by chance one of the most popular ski boot heaters on the market. This is shown by the growing number of users. Anyone who wants to ski, hiking, run or mountain climbing even in the harsh winter conditions and if there is a problem with cold feet, there will be no problem in enjoying any outdoor activity using these high-quality Hotronic S4 Footwarmer.

If after reading this Hotronic S4 Boot Heater review, you think for some reason this is not the right product for you, then take a look at our best selection of the ski boot heaters on the market here and we hope you will find your ideal heater for your ski boots or your winter footwear.

Written by Miki Ristovski

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