Review of Thermalution Heated Vest (Yellow Grade)

I wanted to wait a few months before finally writing a review for the Thermalution Heated Vest.  On a whim I purchased the Thermalution Heated Vest (Yellow Grade Plus) with the wireless remote controller.  I’ve been looking into getting an active heating system for use under my drysuit for some time but it has been hard to stomach the costs when I know the incredible markup on a lot of dive gear.

The Thermalution heated vest is an intriguing one.  Thermalution is a Taiwanese company / manufactured vest that is designed to work under a wetsuit or a drysuit.  The added bonus here is that if your drysuit floods it should still be safe to run your heated vest.  I really liked this idea and especially like the ability of being able to use this vest under a wetsuit.  It think it will be really good for winter diving in Mexico especially in the caves with a 7mm wetsuit.

Before I bought the vest I asked a lot of people for opinions on it.  I know 3 people locally that own them and they all seemed to be very happy with the vest.   Granted I don’t believe any of the 3 have experience with other manufacturer’s heating systems so it’s sometimes hard to get get good opinions and facts.   When I was in Scapa Flow in Scotland last month, there were also about 4-5 people on the boat that had these vests and they seemed to also like them.

A lot of the negative opinions I got were from people that honestly had never used them or tried them.  The chief concern about these vests are that the batteries are inside your drysuit.   I think it’s a valid concern. Most other systems on the market designed for drysuits use a bulkhead that goes through your drysuit inflator that connects to an external battery / power pack.  The benefit here is a way to isolate the battery in the event the heated vest or battery malfunctions.  External batteries are often much larger providing a greater runtime and wattage of a heating system.

The Thermalution vest has been batteries that are inside the suit. The removable batteries attach to the vest on the sides underneath your armpits.  They are unobtrusive and out of the way.  This means a few things. For one, you don’t need to install an additional hole or new bulkhead in your drysuit with wires.  You also don’t need to carry an external canister battery to run this heated vest.  The downside of course is that if these batteries or the vest malfunctions you really have no way of isolating the batteries.    The vest (Yellow Grade) is designed to be controlled with a wireless remote control (also waterproof) that allow you to turn the vest on/off and to cycle through 3 power settings (low/medium/high).

Ultimately it’s a risk-weighted decision that you will have to make on your own.  The batteries and vest are supposedly waterproof to 300ft (~90m).  If your drysuit floods the beauty here is you can continue using the heated vest as it’s also designed to work under a wetsuit.    In the world of exploding laptop batteries and cellphones being banned on airplanes due to battery explosion it’s a very valid concern.   Nevertheless..it is a risk I’ve decided to take, after all I figure I am already diving on a rebreather, sometimes in a cave or wreck (overhead environment)… What’s wrong with adding a little electric shock therapy or potential burn risk?   If you want to avoid all risks I suggestion staying inside your house and never going outside. Don’t bother scuba diving; it’s too dangerous.

First impressions?

The packaging is nice and the vest seems well put together.  The Thermalution manual is completely atrocious and might as well be written in Chinese.  Actually..I’m sure it was at some point.   It’s so badly translated into English (Engrish!) that I sincerely hope their engineering department has a better grasp on these things than their marketing or technical writing department.  Note: Thermalution if you’re reading this please hire a better English translator.  You could have the best product in the world but on first impressions this doesn’t instill a lot of confidence. Ultimately though the manual, although badly translated is pretty straight forward and it doesn’t take that much to figure out how to use the vest.

The vest itself is like a very thin and tight fitting rashguard.  Not a lot of bulk so it can be worm under your wetsuit or drysuit.   The batteries are on the sides underneath your armpits. I thought they might dig into your sides but I honestly don’t notice them at all.    So far I’ve worn the vest under a full 5mm wetsuit in the pool (over another rashguard) and under my drysuit. I had it sandwiched between two polypropylene base layers over a set of Fourth Element Artic undergarments.

Important: They recommend not putting the vest on next to your skin.

I actually tried this for an hour while sitting on the couch and I had a nice red pattern on my back from the heating element.  It didn’t burn my skin or anything but you could make out the outline of the heating element on my back for about 5 minutes.

Wireless Controller

The wireless controller is pretty small and can be stored in a pocket or clipped to a d-ring. It uses inductive charging so you don’t need take out batteries to charge it. I’m not even sure if the wireless controller is meant to be opened up anyway.  You cycle through the 3 power settings for the vest with a toggle switch.  There is one LED on the controller that has 3 colors to indicate which setting you are on (green for low, orange for medium and red for high).  It will blink every few seconds to let you know it’s on.

I kept the wireless controller clipped to the d-ring on my BCD while in the pool. In my drysuit I clipped it inside the side thigh pocket to keep it out of the way.

Diving the Thermalution vest in the pool under a wetsuit

For it’s first actual test I wore the thermalution heated vest for a ~4 hour pool session on low under my 5mm full wetsuit that is very well “loved” and compressed. The pool water is 79f but I honestly always leave the pool shivering.  During open water classes I’m doing a lot of briefings on the surface and there is sometimes not a lot of swimming around.  Even in a 5mm I get cold and I have lots of natural bioprene to help insulate me.

What can I say? The vest worked awesome. It seemed to stay on for the entire pool session so at least on low the advertised runtime is accurate. I did not come out of the water shivering. That to me is a huge improvement.  I did feel bad for my students so I had to specifically warn them to let me know when they were cold since I had a slight unfair advantage here.

Drysuit Diving

The real test here would be up in Esperanza quarry where the water temperatures are never above 39f-40f (~4c).  This is one of my primary reasons that I wanted to get a heated vest.  It’s very difficult for me to do more than two 60-70 minute dives in 39f water.   I am at the point now where I am wearing too many layers and losing flexibility.  I typically wear 3 mid-to-heavy weight base layers and two sets of long johns under my Fourth Element Artics undergarments. I know that ultimately upgrading to warmer undergarments will obviously help but I wanted to do both.  I’m looking at picking up a set of Santi BZ400, Fourth Element Halo 3Ds or DUI 450gr undergarments at some point but I figured I would get the heated vest first and buy some newer undergarments later this winter.

I put the Thermalution vest to it’s first test this Saturday (EDIT: this was a month ago..) when I went diving with my buddy Tom H. at True Blue / Esperanza Quarry.  The air temperature started out in the low teens (12F / 11C when I was driving through Vermont) and only reached about 25F degrees as we were gearing up.

Although we didn’t do a super long dive I could tell a huge difference. I kept the vest on medium for the entire dive.  I still need to experiment running it on low and high under my drysuit and see how it feels.  I figured low might not be enough and I didnt want to completely drain the battery on high if the runtimes werent accurate.

Dive #1 Max depth: 105ft  Runtime: 52 minutes  Water temp: 39-40f.  I ended up with about 8-9 minutes of deco and the vest seemed to help that. It was so cold in fact that my bolt snaps froze shut on the surface immediately after surfacing. One of Tom’s 2nd stages also started free flowing on the surface.

We ended up only doing one dive on Saturday but I met my friend Matt and Lea on Sunday for a couple more dives.

On Sunday the air temperatures were slightly warmer but still in the low 20s.  Matt’s plastic belt buckle for his can light shattered in pieces due to the cold while one of the plastic buckles on my Shearwater also shattered. Ah the joys of winter diving..

Dive #2 Max depth: 107ft Runtime: 42 minutes. Visibility: 20-25ft Water temp: 40-41F We kept this dive purposely short as Matt/Lea were using their stage bottles to conserve backgas for 2nd dive.

Dive #3 Max depth: 80ft Runtime: 47 minutes. Visibility: 20-30ft (better in some spots) and water temps of 39-41f degrees again.

I kept the vest on medium for both of these dives and turned it off during the surface interval.  The vest was still going strong as I came out of the water after the 2nd dive, granted both of these dives were pretty short.  I want to test it with some longer runtimes and see how I feel.

My core body still “felt” warm but my feet were and hands (even with dry gloves) were cold; I never really noticed this before.  Typically before it’s something my entire body would feel but now I am really only noticing it in my hands/feet.

I still need to do a few more dives with this system before I can really get a better gauge but so far I really like the Thermalution vest. What’s not to like about a heated vest?

UPDATE:  I wanted to wait a while before publishing this post but I have done another ~10 dives with the Thermalution Yellow Grade Heated Vest under my drsyit.  I really like this vest.  I’ve had zero issues so far. I did have a friend who bought one and had their wireless remote arrive DOA (dead-on-arrival) but it issue was quickly resolved by the vendor.  I’m mostly used the vest on Low and Medium settings as I was afraid of killing battery.  Medium has been fine for me in 39F water.