It happens all the time and doesn’t spare any of us. At first, our brain receives alarming signals due to stiffening, cold fingertips. Arteries and veins of the extremities are already withdrawing warm blood towards major organs. You will probably think it’s nothing - I’ll move my fingers a little, I fin a bit faster and it will be better soon. No, it won't.

Next, your brain can no longer focus on anything but the feeling of cold. You become indifferent to the world around you and your dive buddy. Chills and muscle twitching brings relief for only a second, and after a while, you no longer feel whether you are pressing the inflator button or not. You want to ascend as soon as possible, but you are too deep for that. Your buddy doesn’t seem to have the same problems as you, so you don’t want to spoil his dive. You are thinking about showing him the "I'm cold" sign in the next few minutes. The chills stop. You also start feeling your bladder pressing, so you can't wait for the end of the dive - even if you are prepared for it, peeing underwater is not comfortable. You start to get lost in your own thoughts, and you are no longer paying attention to which way you are going. You fall into indifference and apathy, which can lead to a very dangerous situation, threatening the health and life of yourself and your buddy.

This is obviously the darkest scenario describing the crossing of the border called hypothermia. Most technical and recreational divers have some experience in getting close to this level of cold, so the most important thing is to know how we can prevent this from escalating into something worse.

First of all, diving should be safe, pleasant and fun. We are not Navy Seals, we do not fight for life on the sea battlefield, we do not have to prove to anyone how tough we are.

We are warm-blooded creatures, which means that the external temperature of our body should oscillate within the limit of 36.6 ̊ C, and our internal temperature should be about 37.2 ̊ C. 2-3 degrees of difference can already strongly affect our well-being and the way our brain works. Water with a temperature below 36.6 ̊ will take the warmth from our body about 25 times faster than air does, which is why divers all over the world must use exposure suits for dives in colder water.

For those who dive in waters located within a temperate climate, the cold accompanies us at every step of our diving career. It’s near impossible to do a basic scuba diving course in Europe without diving under a thermocline, which can usually be felt at around 9m of depth in summer. Most of us begin our underwater adventure using a wetsuit, which in the early stages of learning how to control your buoyancy works well enough. However, with increasing depth and longer dive times, wetsuits will no longer do the job. Anyone who plans on a year-round active underwater exploration of the most popular dive spots of our region must seriously consider purchasing a drysuit. Fortunately, we have a huge selection in the market, where drysuits can be adapted to all our needs and sizes.

A drysuit gives us freedom and security. Modern solutions straight from NASA have taken us to the future, but sometimes it’s easy to forget that the suit itself does not retain any heat, so it doesn’t actually keep our bodies warm. This kind of suit is only a barrier between our skin and the water, with its sole purpose being to keep us dry. Undersuits and good thermal underwear are what will maintain the temperature of our body and delay the heat from escaping. Many diving equipment manufacturers offer a variety of insulation options for summer and winter, from synthetic to natural materials. Everyone can find something for their diving needs, but if we are diving throughout the year, we definitely need to stock up on a thick, winter undersuit, which reduces our mobility no matter how modern the cut or superior compression quality of the material.

Fortunately, clever designers from diving laboratories came up with the idea of heating underwater. That's right, not support, but heating. This was an extremely important breakthrough solution in the world of scuba diving equipment. On the market, you can now find heated vests, gloves and even whole heated undersuits. Cables run within the insulation material, and can heat to up to 45 ̊ C. Such a tremendous amount of warmth can extend our stay underwater for up to an hour.

Another major challenge was the design of the casing with efficient batteries supplying the heating cables. For example, placing the battery inside the suit poses a large risk of burns. From time to time, the media reports on problems with "exploding" batteries in laptops or smartphones, which results in subsequent bans on bringing such items on board of an aircraft. An example close to home would be the accident of a British diver who suffered a painful burn while descending to a depth of 50m. He dived in a drysuit, inside which he set up his catalytic heater battery-powered chemical heating system. Most likely, the overheating of the poorly protected battery led to a small explosion in the vest, which resulted in a deep chemical burn on the diver's back.

It is fair to say that placing the battery inside a suit results in the inability to react quickly in the event of excessive heat or even ignition before, during or immediately after the dive. As such, placing the battery outside the suit really is the best and safest solution. This allows us to get rid of a problem in a few seconds and avoid painful consequences.

We at Ammonite System are diving lovers just like you. Over the past years, we have collected your opinions, listened to your needs, and tested all possible solutions ourselves. This has resulted in our highly anticipated line of heating batteries - ACCU THERMO SYSTEM by Ammonite System.

As such, we proudly present to you our three brave musketeers:




What connects all our batteries is proven solutions and original, proprietary ideas that you will find only in AMMONITE SYSTEM. The most important thing in every battery is a heart made of lithium-ion cells with unprecedented current efficiency. After connecting the heating elements and torch, the maximum power supply is up to 200W, and DC voltage of about 12V.

As mentioned above, we are divers ourselves, so we know what is useful for demanding technical divers, and we also understand the needs of recreational divers who make shallower dives. There is no need to take excess heavy and unnecessary equipment with you on every dive. All our batteries have a charging port that can be optionally used to connect any of the Ammonite System umbilical torches. This means that one single battery will power your torch and for example a heating vest! However, for deeper dives, we recommend following the principle of equipment redundancy. We should not expose ourselves to a sudden loss of main light and heating at once due to one unexpected failure, as we all know how the domino effect and the accumulation of problems work underwater. When performing advanced dives, we would therefore always recommend to carry separate power sources.

Each of the accumulators has an LED Indicator which shows the battery charge level, as well as a system that tests whether the entire heating system is properly connected so that after the start of the dive there are no surprises.

The LED Indicator is located on the upper part of the casing, right next to the charging and E / O port. Indicates the battery performance status and provides information on the current power level. The LED light up for 4 seconds in a mode corresponding to the level of charge:

  • green, continuous - from 100% to 75% charge
  • green, intermittent - between 75% and 50% charge
  • red, continuous - between 50% and 25% charge
  • red, intermittent - less than 25% charge.

All the batteries also have modern, electronic protections against deep discharge, over-charging of cells and undesirable overload and short circuit.


With slightly stiff fingers and thick gloves, handling small buttons, switches or zips can be extremely difficult and annoying. That is why our batteries come equipped with a reliable magnetic switch, which has a pronounced stroke even with the thickest gloves or shapely hands. Two-stage power control means effective power management and extends battery life.

Our standard cable is the “Intelligent” E/O cord, which is an electronic system that protects the E/O cable connector against external damage. This smart system is also equipped with sensors that cut off power when the cable is disconnected and recognises when to restore it when reconnected. In practice, this means that when you dive without the heating device cable plugged in, nothing bad happens to your battery and E/O cable! You can then plug your heating system in and disconnect during the dive as needed.

We know how stressful packing equipment before travelling by plane can be, so it’s something we also took care of. The transport of lithium batteries is subject to international regulations, which vary depending on whether transport is by sea, land or air. All our lithium-ion (Li-Ion) batteries meet the requirements of UN Transportation Testing (UN/DOT, 38.3) standards. To ensure safety in transport and guarantee your successful trip, we provide UN 38.3 certificates, which you can show to airport security staff.

Heating batteries from the ACCU THERMO series are a guarantee of reliability packed in solid casing protected by two O-rings and a safety valve. Their small size is ideal for attachment to the waist belt or wing plate. They are compatible with heating devices of all the most popular manufacturers and come with a full 3-year manufacturer's warranty.

What is the difference between our cold musketeers?

In terms of the casing, ACCU THERMO TYPE 14 and ACCU THERMO TYPE 24 are made of a combination of light and durable polymer (Delrin®) and hard-anodised aluminium. The first of them has greater resistance to high water pressures, as much as 16 ata or about 150m deep. TYPE 24 is prepared for pressure up to 11 ata or about 100m deep.

ACCU THERMO TYPE 24 SPECIAL is a battery designed for the most demanding divers with extreme needs. It is made of hard-anodised aluminium, resistant to corrosion in salt water, the toughest weather conditions and mechanical damage - even scratches. We have ensured its proper functioning up to a pressure of 21 ata, i.e. about 200m!

ACCU THERMO TYPE 24 SPECIAL and ACCU THERMO TYPE 24 have a nominal capacity of 23.45Ah , which provides a lot of positive energy underwater (measured at 100% light):

  • Heated gloves 30W - 8h
  • Vest 55W - 4h 20 '
  • Undersuit 110W - 2h 10 '
  • Gloves +  vest - 2h 50 '
  • Gloves + undersuit - 1h 45'
  • Charging time - 8h

For divers who do not spend 90% of their life underwater or those who are looking for a spare battery for advanced dives, we recommend ACCU THERMO TYPE 14. Divers can use this battery effectively to power a smaller number of heating devices, and the possibility of quick charging will make repetitive dives a lot less hassle. TYPE 14 with a nominal capacity of 14Ah will satisfy any scuba diver, not only recreational (measured at 100% light):

  • Heated gloves 30W -4h 50'
  • Vest 55W - 2h 40 '
  • Undersuit 110W - 1h 20 '
  • Gloves +  vest - 1h 40 '
  • Gloves + undersuit - 1h 20'
  • Charging time - 4h

Being warm underwater is not a sin! Let's ensure our comfort, allow ourselves more pleasure from underwater trips to another world and increase diver safety as much as possible. The AMMONITE SYSTEM and our battery line is made for us.