Shelly H&T and the Shelly Smoke – Battery Powered Humidity / Temperature / Smoke Sensors

December 5, 2018

Today on the hookup we’re going to take a look at two pretty unique new products from shelly, and figure out if they are worth adding to your smart home.

For a few months shelly has been posting on their facebook page about two new battery powered products that they have been developing.  Earlier this week they sent me some of the first production run for the Shelly H&T and the Shelly Smoke to review.  I’m going to put both of them through their paces in this video, but we’ll start with the smaller and more portable of the two: The shelly H&T.

Like other devices that we’ve seen from shelly, the H&T is extremely small.  It’s basically the exact same size as a golf ball, but with a flattened top and bottom to be able to set it on a surface without it rolling away.  Inside the H and T is a lithium CR123A battery strapped to a small board with an ESP8266 chip.

On the top is a button that puts the H and T in configuration mode where the wifi chip stays awake for roughly 3 minutes to get it properly setup.  Keep in mind that this is a pretty serious drain on the battery, so get it setup and then leave it alone.  Also, because the ESP8266 heats up when in use you should expect temperature readings to be slightly higher than room temperature when in setup mode.  Once the wifi radio is sleeping the temperature readings become accurate.

There is also a GPIO header similar to what you’d find on the shelly1 for flashing custom firmware, however, keep in mind that the software on the H and T relies heavily on putting the wifi radio to sleep to maximize battery life and provide accurate temperature monitoring, so unless you really know what you’re doing I wouldn’t mess with the firmware.

I would not advise putting tasmota on this device.

The H and T is triggered to send data both by an hourly schedule that you can adjust, oy by a change in temperature or humidity.  You can set the threshold temperature and humidity changes that trigger a wifi transmission via the web interface.

In order to increase battery life, Shelly also recommends that you use a static IP for the device to decrease the amount of time that the wifi radio needs to be on, since wifi is responsible for well over 90% of the battery drain.

By default the H and T works with the shelly cloud app, but Just like other shelly products you can configure it to use your local MQTT server instead.  It transmits three separate messages on these three topics each time it wakes up, the first is the current temperature, the second the current humidity, and the third is the battery percentage.  I’ve included the YAML that I used to add the shelly H and T to home assistant in the description below.

I’ve only had the H and T setup for a week so I can’t speak to the longevity of the battery, but it seems like if you avoid pressing the configuration button too often you should expect about 1% battery drop every 3 to 4 days, so assuming it will continue to function all the way down to 0% battery you can expect about a year of battery life.  If your house’s temperature fluctuates rapidly then you might see less battery life, if you have a well insulated house your H and T will wake up significantly less and you may see a longer battery life.

Now that we know what it is and what it does, we need to discuss the most important aspect, what role does it fill in your smart home?

One of the main advertised features of the H and T is to use it in conjunction with a smart outlet or a smart relay to turn on localized heating or cooling for a specific room.  My house was built in 2012 and has two central air units, one for upstairs and one for downstairs.  My heating and cooling is controlled by two ecobee smart thermostats so I don’t have much use for the H and T for this particular purpose.

The shelly H&T also works in the refrigerator to monitor temperatures and humidty if your family is prone to leaving the refrigerator door open, and it could even work in the freezer, which I know would have been extremely well received by my wife when she was breastfeeding my daughter and stockpiling breastmilk in the freezer.  She was constantly worried that the freezer would fail and she would lose her saved liquid gold.  Now that our daughter is 6, if our freezer failed we’d mostly just lose frozen dinners and ice cubes.

I have discovered that using the shelly H and T in your freezer does strange things to the battery.  My battery reads about 90% outside the freezer, and under 70% inside the freezer… clearly this is because chemical reactions are affected by temperature, but I was surprised at how significant the change was.  After being removed from the freezer the battery % slowly recovered to the same 90% level as before.

I know there are plenty of people out there who have much more complex heating and cooling solutions I their home and the shelly H and T may be the perfect device to enable smart control of those existing systems, it just doesn’t add a whole lot to my particular smart home.  If I’m missing some obvious important application of the H and T please let me know in the comments.


The shelly smoke however, is a product that I’ve been looking forward to reviewing and buying for months now.

First of all, let me say that smoke detector laws are no joke and they exist to keep you and your family safe.  I’m very willing to take on the risk and responsibility that comes with working with electricity when installing smart home equipment, but one thing I have absolutely refused to do is modify the smoke detector system in my house, but I also want to be alerted if I am out of the house and the smoke alarms have been activated.

The shelly smoke is a wifi enabled battery powered photoelectric smoke alarm, and in true shelly fashion, it’s also really small.  In addition to monitoring for smoke, the device also reports temperature in a similar fashion to the shelly H and T where you set a threshold temperature change to cause it to wake up and report its current status.

The shelly smoke is not a replacement for your current smoke detector system.  In the US there is very specific fire code that governs smoke detectors.  In new construction all smoke alarms must be interconnected so that if one of them is triggered they will all sound.  The shelly smoke cannot interface with these systems and therefore wouldn’t pass inspection.  But by placing a shelly smoke on each floor of your house in addition to your pre-existing smoke alarms you enable wireless notification of smoke events if you are out of the house.

It’s also worth noting that the shelly smoke is not a flame detector, it is a smoke detector.  Photoelectric smoke alarms work by detecting haze in the air, this haze could be caused by smoke, dust, or even steam.  Ionization alarms are for fast growing fires that don’t emit much smoke, whereas photoelectric detectors like the shelly smoke are for slow building fires that often produce significant amounts of smoke.

Inside there’s not much to see, it’s a battery, a buzzer, the actual photoelectric detector unit and the board containing the esp8266.  If you’d like more information about small photoelectric smoke detectors bigclivedotcom did a great destructive teardown of a very similar, but not wifi enabled unit on his youtube channel.

I did test the shelly smoke in some different situations like putting it over a candle I had just blown out and a pot of boiling water and it functioned exactly as expected in both cases quickly sounding the siren until the smoke or water vapor had cleared.

I love the shelly smoke and I’ll be purchasing two more of them to install in my house.  I’m going to put one upstairs, one downstairs, and one in the garage,

My one gripe with the shelly smoke is that it doesn’t also include a carbon monoxide detector.  I’ve spoken recently with the shelly CEO and he has told me that a standalone carbon monoxide detector is in the works, but that it is not planned as an upgrade or addition to the shelly smoke.

To setup the shelly smoke you’ll follow a similar method as the shelly HT.  FYI, when you receive your shelly smoke it will have a small piece of plastic preventing the battery from contacting the terminals.  Be aware that when you pull this plastic off initially it will beep loudly two times, most of the time I’m sure that won’t be an issue, but if you’re unboxing it at 10pm while your wife is fast asleep on the couch it doesn’t go over well.

After you initially power the shelly smoke you can connect to it via the shelly app, or if you plan on using local MQTT to add it to your home automation platform like me you can just connect to the wifi access point generated by the shelly and navigate to to access the web console.

From there you can put in your wifi information and hit save.  Once the shelly smoke is on your home network you can put in your MQTT information, change settings, and update firmware.  If at any time your shelly smoke goes back into it’s deep sleep cycle you can press the button on the side to wake it up for another 3 minutes, make sure you use a single short press, a long press will reset it back to factory settings and you’ll need to connect to the access point again.

Once you’re all set up the shelly smoke sends 3 messages whenever it wakes up from sleep.  The three messages are on these three MQTT topics, the first is for the current temperature, the second is for the presence of smoke and the third is to report the current battery percentage.   Just like the shelly H and T, The YAML I use to add the shelly smoke to home assistant is down in the description, you’ll just need to update it with the MAC address of your device.

The shelly H and T has just become available for purchase today for around twenty dollars via the shelly cloud website, no word on when it will be on amazon.  The shelly smoke will be available in early January and will be priced around forty dollars.  I’ll be sure to post an update when they can be purchased.  New shipments of the shelly 1 and 2 should be available on amazon as early as this afternoon, links are down in the description.

In other updates, Eric Powell suggested I try out the ESPixelStick firmware on my houseLEDS and after a dozen or so hours of learning how to sequence in xlights I’ve got a sweet music light show for this holiday season.  I’m still planning on making a plug and play music sequence with my year round holiday LED code, but this is a great stepping stone for me to learn the ins and outs of sequencing

I’m also excited to announce that I’ll be attending CES this year from January 8th -11th in Las Vegas.  I’ll be wandering around trying to find cool new products for the DIY smart home community, and I’ll also be spending some time at the Shelly booth.  If you’ll be attending CES and you’d like to meet up shoot me a note on twitter, or my email and we can make it a date.

Thank you to all my patrons over at patreon for your continued support, you motivate me to find time for this hobby even when life gets crazy.  At the suggestion of a few of my viewers I’ll be following in the docs footsteps and making a walkthrough video of my smarthome when I hit twenty thousand subscribers, so tf you enjoyed this video, please consider subscribing.  And as always, thanks for watching the hookup.

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